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Chapter XIII

Contents

CHAPTER XIII

The Epidemiology of Cold Injury

GENERAL CONSIDERATIONS  

    Studies made in ETOUSA (European Theater of Operation, United States Army) during the winter of 1944-45 clearly showed that cold injury is a component of mass trauma and that is behaves in accordance with epidemiologic laws. It was thus demonstrated again that the biologic principles that govern disease as a community problem hold equally well for trauma, including trauma caused by cold.
       
    Before cold injury is discussed from this point of view, certain general facts concerning epidemiology must be stated, as follows:
       
    Epidemiology, according to Gordon,1 may be defined as medical ecology and may be interpreted as the influence of the total environment upon the reactions of living things. By this concept, health is the equilibrium of all the factors which come into play to influence disease or injury in man. Agent, host, and environmental factors make up the total epidemiologic potential, and their equilibrium, or their lack of equilibrium, determines the presence or absence of disease or trauma in any given community.
       
    The agent is the specific cause of trauma or disease. The host, man, has many inherent qualities which predispose him to, or which protect him against, injury or disease. The environment in all its aspects, physical, biologic, and socioeconomic, constitutes the medium through which agent and host are brought together to cause injury or disease. Man's equilibrium in health may become a lack, or absence, of equilibrium in trauma or disease through (1) actions of the agent, (2) reactions of the host, (3) functions of the environment, or (4) the interactions of any two, or of all three, of these epidemiologic potentials.
     
    With the acceptance of this concept, the causation of disease or injury is not limited to any specific micro-organism, or to any single agent, such as cold. Multiple factors are always involved. Epidemiology embraces both multiple causation and the multiple mechanisms through which multiple causative factors interact. An understanding of the effect of the interactions of causative factors is essential to a comprehension of the whole epidemiologic problem. Epidemiologic analysis of total cause and effect is the only sound basis from
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1 Gordon, J. E.: The Strategic and Tactical Influence of Disease in World War II (Preventive Medicine and Epidemiology). Am. J. M. Sc. 215: 311-326, March 1948.  


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which a clear picture of the total situation can be derived; it is also the only sound basis upon which an effective program of prevention and control can be built.  

Application of Epidemiologic Principles to Cold Injury <> 

    All of these generalizations are applicable to cold injury. The specific causative agent is cold, or cold in association with wet. A number of host factors determine the susceptibility of the soldier to these agents. The interplay of agent and host factors is governed by a number of environmental factors.
       
    The total causation of cold injury is complex. This is not so much because any single factor involved is complex but because of the interrelation of the multiple factors which come into play to make up the mechanism of cold injury under variable circumstances. It is not at all difficult to classify these several factors according to agent, host, or environment. What is difficult, in the analysis of the over-all problem, is to determine the relative weight. which should be assigned to each single factor.
      
    Interpretation of World War II experience of cold injury.- The interpretation of the cold injury experience of World War II may be approached in several ways, as follows :

    1. The first approach is an endeavor to interpret this experience from the point of view of broad causality. It has been established historically, both by experiment and experience, that cold and wet, singly or associated, are the preeminent causal factors in cold injury. They are the conditions which must be present if it is to occur. Historically, mass cold injury has occurred only in time of war, only then in the cold or wet-cold season, and only then under circumstances of military stress that bring about unusual exposure of the soldier. Exposure has two components, degree and duration. Time, or duration, thus becomes an additional component of broad causation.
       
    With these fundamental concepts established, it is possible to investigate how the several modifying factors of agent, host, and environment impinge upon the core of causation. The chronicle of cold injury in World War I and the field investigations of cold injury carried out in World War II were along these lines and pointed toward the determination of the factors which made up total causation.
       
    2. In view of the constancy of the basic causative factors of cold injury, that is, cold and wet, a second approach toward the problem is logically directed toward the study of modifying factors. This particular study is limited to individual factors or to circumscribed groups of the several causative components of cold injury. The effect of cold injury is readily measured in terms of numbers of cases and time lost as a result. It is difficult to count and measure the modifying factors which may chiefly determine the prevalence of the injury. Many of them are intangible host factors, such as fatigue, nutritional status, or the effect of a previous cold injury. Environmental factors such as command leadership, discipline, and training are even more difficult to measure precisely.


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    It would have been fairly simple to measure the agent factors of cold and wet in World War II if detailed records of temperature fluctuations and precipitation had been made a part of the record of each division. They were not. Average weather data were recorded by army areas, but in no theater do records exist of the detailed day-by-day fluctuations within division areas.
       
    3. A theoretical method of approach is to assign relative values to each of the factors implicated in cold injury and to study the trenchfoot record in each division in the light of these values. This method permits a composite evaluation of the circumstances which are favorable and unfavorable to trenchfoot. As a practical matter, when this method was used, low ratings generally were associated with good division records for cold injury, but the distinctions were not drawn finely enough to establish reliable quantitative multiple-factor relationships.
       
    Twenty-one infantry divisions in the European theater were rated by this method for the months of November and December 1944 according to type of combat action, clothing supply, rotation, training and experience, shelter, and terrain, in addition to the basic factors of cold and wet. Details of this study are recorded elsewhere (p.366). In general, it may be said that the selection of qualitatively significant factors by multiple correlation techniques was restricted by lack of precise measurements for factors presumed to be important on the basis of previous experience. Significant correlation could be established between the cold injury experience and the degree of combat, as well as cold injury and shelter. Significant correlation could also be established, though to a lesser extent, for rotation as well as terrain. Had more precise data been available, multiple regression studies of these factors might have made possible the assessment of relative factor weights.
       
    However, in spite of its limitations, this study bore out, in general, the ratings already established for the various divisions in relation to their cold injury records. It also confirmed the feasibility of evaluating the modifying factors in cold injury for which precise quantitative measurements are not available.
       
    4. In the absence of data ample enough and precise enough to permit statistical measurement of the influence of such factors of concern to the individual soldier as leadership, training, clothing, fatigue, or foot discipline, some other method had to be found to assess the role of these and other factors involved in cold injury in World War II. None presented itself except the epidemiologic approach of studying organizations ranging in size from battalions to divisions by the selection of periods of time and situations in which only one factor seemed to vary in comparison with other organizations of similar size operating under identical or almost identical conditions.2 This method, which is applicable to agent, host, and environmental factors alike, has been utilized in this chapter to study the modifying agents of cold injury. All possible factors
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2 All data concerning the various divisions and other organizations used for unit case histories and other studies in this chapter were obtained from the appropriate records on file in the Office of the Surgeon General of the Army.


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have been evaluated by this method. In addition, the influence of certain of them has been assessed in part by the rating method and statistical procedures already mentioned.  

ANALYSIS OF SELECTED DIVISIONS BY CORRELATION STUDIES <> 

    The experiences of 21 divisions on the Western Front in November and December 1944 were studied, by the technique already described in the light of six factors of environment, in an attempt to weigh the impact of these factors on the incidence of trenchfoot. These factors, namely, combat action, rotation policies, weather, shelter, terrain, and troop experience, constitute the independent variables among which interaction may take place. The dependent variable is the incidence of trenchfoot.
       
    Since none of these factors are susceptible of quantitative grading, a subjective scoring of their intensity was set up (see footnote 1, table 11), ranging from (1) least predisposing to (4) most predisposing. Each division was then rated separately for November and December, and the data were recorded, together with the actual numbers of cases of cold injury each had experienced (tables 11 and 12).
       
    Data concerning temperature and precipitation could not be weighed in relation to other factors because, as already noted, they are available only as means for whole army areas and thus do not fluctuate by division. Similarly, criteria for measuring training and experience are gross and thus do not vary significantly between the divisions or between the 2 months covered by the analysis.
       
    Clothing supply was a theater problem. All divisions were affected to some extent. No division was without supplies, but no division was fully equipped. Variations between divisions in this respect were not great, and the moderate improvement which occurred in December affected them all. The influence of this factor can therefore be judged only by isolated circumstances, such as were created, for instance, when overshoes were left behind by order.
     
    Before a statistical analysis of these data was undertaken, it was necessary to find a linear function of the incidence which was roughly related to the independent variables. The logarithm of the incidence was found to fulfill this requirement. Next, the usual procedure of computing correlation coefficients was applied for each of the six independent variables and the dependent variable (table13). The coefficients of combat action and shelter were found highly significant. Those of terrain and rotation were of borderline significance. The paradoxical finding that the coefficient of weather, which is a basic factor, was entirely insignificant could be explained only by the nature of the data. As pointed out earlier in this chapter, these data were general and incomplete. During the period chosen for the study, the weather seems


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TABLE 11.- Scores of 21 infantry divisions, European theater, by cold injury modifying factor, November 1944


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TABLE 11. -  Scores of 21 infantry divisions, European theater, by cold injury modifying factor, November 1944 - Continued


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TABLE 11.- Scores of  21 infantry divisions, European theater, by  cold injury modifying factor, November  1944  - Continued
 


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TABLE 12.- Scores of 21 infantry divisions, European theater, by cold injury modifying factor, December 1944


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TABLE 12.- Scores of 21 infantry divisions, European theater, by cold injury modifying factor, December 1944 - Continued


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TABLE 12.- Scores of 21 infantry divisions, European theater, by cold injury modifying factor, December 1944 - Continued


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to have held fairly constant, so that it could not greatly influence variations in the trenchfoot incidence. The correlation coefficient for training and experience versus incidence can be disregarded, since it was rather low.

TABLE 13 - Cases of trenchfoot in 21 infantry divisions, European theater, November and December 1944, in relation to ratings of several predisposing factors

     Of the four apparently significant factors left after those just discussed are eliminated, shelter and terrain appear to be of the same nature, both being determined by the topography of the area. It is therefore feasible to combine them in one score by simply averaging the individual scores. With the combined score, a significant correlation is found with trenchfoot. The weighting of each of the three factors, rotation, combat action, and shelter-terrain, is possible, by means of multiple regression analysis. However, this complicated procedure would scarcely be profitable, since it would reflect only the relative weight within this particular situation, while other relative weights might be applicable to other situations, in another area of combat, for instance, or in another season. The relative importance of the three factors cannot be evaluated, but some interrelation can be found by the first order of correlation coefficients between their independent variables. There is a certain interaction between combat action and rotation (table 13) but no correlation between rotation and shelter. A third significant correlation between combat action and shelter adds further uncertainty to their evaluation.
       
    The result of this analysis can therefore be summarized as follows: In an area with relatively bad weather, factors of the military environment were of more importance than weather in determining trenchfoot. Among these, combat action and shelter seemed to be of highest importance. Rotation policy was less influential. No relation between trenchfoot and troop training and experience could be found. Thus, within the broad causation of trenchfoot, certain factors of environment were found to influence incidence  


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CHART 6.- Trenchfoot incidence rates, United States and British forces in Italy, October 1944 through March 1945

when the weather was highly favorable for the occurrence of this special type of cold injury.
       
    This analysis of cold injury in 21 divisions on the Western Front in November and December 1944 does not entirely bear out the epidemiologic findings of detailed unit surveys presented later in this chapter, especially in regard to such factors as the influence of weather, training and experience, clothing supplies, and rotation. The discrepancy, in itself, emphasizes the need for much more detailed data by units if, in the future, a valid statistical analysis is to clarify the roles of the several modifying factors in the causation of cold injury.
       
    Interaction of combat action and season.- The statistical analysis just recorded was limited to a short period of the winter in Europe which was highly conducive to the occurrence of trenchfoot. Data on the incidence of trenchfoot among United States and British troops in Italy from October 1944 through March 1945 throw a different light upon certain factors. Trenchfoot was more frequent among United States troops, as is shown by the rate by months (chart 6, table 14). Combat action, however, varied for the two forces, as shown by battle-casualty rates. It is possible to correct the trenchfoot incidence for combat action by relating the rate of trenchfoot to that of battle casualties. When the rates thus obtained are plotted against the months of occurrence, two facts emerge. The first is that there is a distinct seasonal effect, with the peak in January and February. The second is that the apparent difference between British and United States troops seems to be without significance (chart 7, table 14). The interesting point in these data is that the seasonal


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CHART 7.- Comparison of ratios of trenchfoot to battle casualties in United States and British forces in Italy, October 1944 through March 1945
 
TABLE 14.- Comparative incidence rates for trenchfoot cases and battle casualties, United States and British forces in Italy, October 1944 through March 1945


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factor was originally hidden by interaction with the military operation. The severest combat action took place during the months when the temperature was highest, but the trenchfoot incidence was apparently the same throughout the whole period. When the interaction of combat action and season was dissolved, however, the relatively higher incidence of trenchfoot in the colder months became evident, and it was then possible to explain the differences in the incidence of trenchfoot in the two forces by differences in their exposure.
 
EPIDEMIOLOGIC ANALYSIS OF AGENT, HOST, AND ENVIRONMENTAL FACTORS
 
Agent Factors
 
    Cold.- Cold is the predominant agent in the production of cold injury, just as it is also the immediate exciting cause of tissue damage, irrespective of the influence of extraneous modifying factors. If the effect of cold is described as loss of body heat, the role of wetness as one of the modifying factors in cold injury is more easily comprehended. Experimental studies, the experience of armies in previous wars, and the experience of Arctic explorers and of the inhabitants of cold countries leave no doubt of the part cold plays in the production of cold injury.
       
    The role of cold and the mechanism of the production of cold injury have been described in detail elsewhere (pp. 404 and 235) .
     
    Man is a tropical animal and is therefore highly susceptible to the effects of cold. The temperature of the human body and, to a lesser extent, that of the feet is kept independent of the temperature of the environment by two mechanisms. The first is natural means, such as metabolism and the circulation. Metabolic heat is distributed to the periphery by way of the circulation, upon which the hands and feet are particularly dependent for the maintenance of a temperature independent of that of the environment. Any factor that tends to impede the circulation (p. 390) would therefore be expected to render the hands and feet more susceptible to the action of cold.
       
    The second means by which the temperature of the body is kept independent of that of the environment is artificial, the use of clothing. When man is reasonably well clothed, lie is not greatly affected by dry cold above the freezing point. This was clearly established by the experience of British troops in World War I. Losses from trenchfoot were promptly and markedly reduced by the simple expedients of using trenchboards and wearing gum boots, which allowed the men to reach the trenches dry-shod. After these measures had been adopted, exposure to moderate degrees of cold (from above freezing to 50º F.(10º C.) did not cause significant cold injury.
       
    The evaluation of cold as an agent factor in the production of cold injury would be simple if the effects were in direct proportion to temperature. Then a simple relation between temperature and duration of exposure could easily


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be expressed. The situation is not so simple. The effect of cold as an agent in cold injury is, as already indicated, best described as a loss of body heat, a concept which serves to explain the role of wetness as a modifying factor. Since loss of body heat is the important consideration, the relation of cold and of several other factors becomes complex. Heat loss may be much greater at temperatures above freezing than it is at temperatures below this level if wetness or other factors expedite the process. The loss may be much less at temperatures below freezing if the soldier is properly insulated with clothing and can keep dry. Under these circumstances, it is both expedient and advisable to regard cold as an agent in cold injury which acts in the same manner in which a bacterium acts as the agent in an infectious disease. Similarly, it is well to view the modifying factors that determine the extent and seriousness of cold injury in the same way in which various circumstances may influence the invasiveness of micro-organisms.
       
    Wet.- In the causation of cold injuries that occur in the range of temperatures above freezing, the synergistic relation that wet bears to cold may again be compared to the synergistic relations of certain micro-organisms to each other in the causation of infectious disease. Because of the physical properties of water, wetness enhances the effect of cold. Body heat is readily conducted to the outside atmosphere from the feet and other parts of the body through wet stocks, shoes, gloves, and other articles of clothing. Evaporation of water in wet clothing occurs with substantial additional cooling effects, even when the outside atmosphere is cold and humid.
       
    Wetness has other undesirable effects. It causes clothing to cling closely to the skin and thus eliminates the insulating layer of air ordinarily present between the skin and the clothing. Air spaces between layers of clothing and air in the interstices of the clothing are also lost when the clothing is wet. Dry, intact skin, because of its horny layer, has inherent insulating properties that are destroyed by wetness. Finally, water or wet clothing in contact with the skin for long periods may cause maceration, which in turn increases the likelihood of trauma and infection.
       
    The synergistic effect of wetness is highly important because many military operations conducted in winter take place at temperatures at which wetness combines with cold to produce cold injury. Since cold, as temperature, and wetness, as precipitation, are components of weather, and in this capacity are also environmental factors, both will be discussed in greater detail under the latter heading (p.404).

Host Factors
 
    The host factors responsible for cold injury are inextricably interwoven with the same human attributes that cause soldiers to perform well or poorly in battle, that build up high morale or result in indifference, and that motivate men to fight to the bitter end on one hand and to desert on the other. These are human attitudes, traits, and resources. They are, at one and the same time, physical, mental, and emotional. No precise standards of measurement are


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available for them, but a full understanding of them is the essence of leadership and command function.
       
    Leadership and personnel have been accorded a vast amount of study in the past, and extensive research on human action, attitude, and motivation are currently under way. In some of these studies, great emphasis has been placed upon the psychology of war and on leadership, while in others the chief attention has been given to physical attributes. There is considerable doubt, however, whether all of these studies, and the knowledge derived from them, have been utilized to the best advantage. It has been proposed that the Armed Forces might, with full justification, establish and support research to study man as a whole and to evaluate influences of all kinds, physical, mental, emotional, environmental, and all others that combine to cause men to react and perform as they do. Until this or some similar approach to the measurement of human host factors can be accomplished, it will be impossible to evaluate thoroughly the factors that influence cold injury, combat trauma, neuropsychiatric conditions, and disease.
       
    Because of the absence of satisfactory methods of measurement, the evaluation of host factors is necessarily imperfect. It is based on observations made in wartime, opinions, and such crude measurements as are possible. Nonetheless, by these methods, the important role of host factors is made clear, as is the need for greater understanding of them and for precise methods of measuring them. In spite of these lacks, the crude methods necessarily used in World War II made clear the important role of host factors. The questionnaire submitted to 1,018 trenchfoot casualties and to an adequate control group toward the end of the war (p. 400) furnished material that, together with unit observations, demonstrated both host and environmental influences.
       
    Age.- No conclusive evidence exists that age, per se, influences individual susceptibility to cold injury in the age range of military combat soldiers; that is, 18 to 35 years (table 15). Observations on shipwrecked mariners and passengers suggest that persons below the age of 17 and above the age of 40 years may be more susceptible than those in the years between. These phenomena can be explained by the instability of the cardiovascular system, its inability to adjust to stress in the younger group, and the generally lowered adaptability of the circulatory system in those in middle age and older.
       
    In 1,018 trenchfoot casualties surveyed in Zone of Interior hospitals in 1945 (p.400), age distribution bore no relationship at all to cold injury (table 15). These were chiefly combat troops, and the age range was narrow. Age seemed similarly without influence in the 144 patients with trenchfoot who were surveyed by Berson and Angelucci 3 in hospitals in Italy and who were compared with 877 soldiers hospitalized for other reasons.
       
    In one sense, age does play a role in the susceptibility to trenchfoot. Observations made at the 1st Arctic Aeromedical Laboratory and reported by
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3 Berson, R. C., and Angelucci, R. J.: Trench Foot. Bull. U. S. Army M. Dept. No. 77, pp. 91-99, June 1944. 


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Miller 4 emphasize the importance of physical fitness in withstanding the stress of cold. Since physical fitness is, as a rule, likely to be less in older age groups, an increased individual susceptibility probably could be shown in them. In combat units, however, this would not hold, since the physically unfit are screened out by intent at the time of induction and by the exigencies of battle experience if they have passed the initial screening.
 
TABLE 15.- Age at last birthday of 1,018 patients with trenchfoot, hospitalized in Zone of Interior
 
      Sex.- No data came out of World War II to justify the consideration of sex as a host factor in susceptibility to cold injury. This might be expected because of the military circumstances. Members of the Women's Army Corps were not exposed to conditions conducive to cold injury. They were utilized in the larger headquarters and in hospitals and, in both locations, had shelter, food, and ample clothing. Nurses were assigned as far forward as evacuation or field hospitals in army areas, but the installations were always under canvas or in other sheltered locations. The hospital sites, it is true, often became quagmires, but exposure was not great, and adequate clothing, including galoshes, was provided. Furthermore, the nature of their work kept the nurses, for the most part, in heated shelters.
       
    Race and geographic origin.- The role of race and geographic origin as host factors in cold injury is not well clarified by data recorded for either of the World Wars.
       
    Gilcreest 5 recorded the unusual prevalence of trenchfoot among American Negroes in World War I with a great deal of humor, but his comments concerning cold injury among men of this race in combat are neither convincing nor informative. In World War II, observations in training areas in the United States, as well as in Italy and on the Western Front, furnished no indications that United States Negroes or other soldiers native to Southern States
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4 Miller, A. J.: Physical Fitness for Strenuous Work in Relation to the Survival Situation in a Cold Environment. Report of Project XIV, 1st Artie Aeromedical Laboratory, Ladd Air Force Base, Alaska, 1948.
5 Brownrigg, E. M.: Frostbite in Shipwrecked Mariners. Am. J. Surg. 59: 232-247, February 1943. [Includes discussion by Edgar L. Gilcreest, pp. 245-246.]


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were any more or any less susceptible to cold injuries than were other troops. Combat comparisons are not valid because a large proportion of Negro troops were assigned to service organizations and did not suffer much exposure.
       
    Such combat records as do exist, however, suggest a possible racial susceptibility to cold. The 92d Infantry Division, a Negro combat unit, was exposed to cold in Italy, in the winter of 1944-45, when protection was far better understood and clothing far more adequate than in the previous winter. Although the total incidence of trenchfoot in the Mediterranean theater was greatly reduced for these reasons, this particular division supplied one out of every three cold casualties reported. A possible explanation is that the unit was new to combat and lacked the battle training and experience with cold which other Fifth U. S. Army divisions possessed in the second winter of fighting in Italy.6

    It was also observed that trenchfoot was relatively more frequent in Japanese-American soldiers than in other United States troops.7 The rate was high in the 100th Infantry Battalion (Separate), composed of Japanese-American soldiers, although it was attached to a regiment (the 133d Infantry) in which the rate was low because foot discipline was excellent. The explanation offered by the commanding officer of the regiment was that Japanese-American soldiers were peculiarly susceptible to cold injury because of the delicate construction of their feet. The regimental surgeon was of the same opinion.
       
    Not a great deal of information exists about other troops. In World War I, the French used Senegalese troops on the Western Front in 1917 and had a high incidence of "frozen feet" in the middle of April, when cold injury was negligible among other French forces. Brazilian and Hawaiian troops fighting in Italy in the winter of 1944-45 had a high incidence of trenchfoot. 8 The original injuries were thought to be more severe than in North American troops, and recurrences were unusually frequent. Inexperience and newness to combat probably accounted for a part of this record, as in the Negro division just mentioned, but racial susceptibility cannot be entirely discounted.
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6 Later studies confirm the Mediterranean experience concerning cold injury in the Negro. In the winter of 1951-52, a special cold injury research team, commanded by Lt. Col. Kenneth D. Orr, MC, made an extended study of the etiologic, pathologic, epidemiologic, clinical, and therapeutic aspects of these injuries. The report of the work of this team was published on 1 April 1953 (Summary of Activities, Cold Injury Research Team Korea, 1951-52, Report No. 113, Army Medical Research Laboratory, Fort Knox, Ky.). This report (p. 418) stated that Negro soldiers proved to be a significantly greater risk for attack by frostbite (6 times) than other soldiers when all environmental conditions were equalized. At the regimental level, the Negro rate was 35.9 per 1,000, compared to 5.8 per 1,000 for white soldiers. Negroes also showed more severe injuries than white soldiers. Differences in tissue susceptibility were neither proved nor disproved.
    
     Additional confirmation of the apparently greater Negro susceptibility to cold injury is also found in a report by Maj. Gen. Alvin L. Gorby, in Essential Technical Medical Data for January-March 1956, United States Army, Europe. During February 1956, the number of reported cases of cold injury exceeded the total reported for the cold injury season of 1954-55. While cold injury was the outstanding morbidity problem during this month, it was considered remarkable that the incidence was not higher and the severity not greater, since the winter of 1955-56 was the most severe in Europe in the past century. On the other hand, while the incidence of cold injury was not inordinately high. a large proportion of the cases occurred in Negro troops, which indicates, as previous studies have indicated, that race is a predisposing factor in this condition.
7 Annual Report, Surgeon, VI Corps, Seventh U. S. Army, 1944.
8 Toone, E. C., and Williams, J. P.: Trench Foot: Prognosis and Disposition. Bull. U. S. Army M. Dept. 5: 198-210, February 1946.


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    The evidence of racial susceptibility to cold is thus fragmentary. It is certainly not sufficiently convincing to prevent the employment of presumably susceptible races in winter operations, such as those in Europe in World War II, although better knowledge of this host factor might strengthen the decision to use certain racial groups in service echelons or in light holding defense operations pending a long period of acclimatization. As a matter of fact, acclimatization and adaptation to climatic environment are difficult to separate from purely inherent racial susceptibility or lack of susceptibility. All races can acclimatize to cold, to some extent, at least, and can learn to do the things necessary for survival in the cold.
       
    The Eskimos furnish the outstanding illustration of this ability. The white man can acclimatize to the arctic cold, but he never develops inherent protective mechanisms equal to those of the Eskimos, who, as the result of long development, undoubtedly possess a racial tolerance to cold. Eskimo babies wear no clothes. They are carried in pouches on their mothers' backs, in skin-to-skin contact, and they are removed stark naked, in weather far below zero, for excretion, feeding, and other care, without apparent harm. The Eskimos, furthermore, know the value of protective clothing and of special care of the feet. All their clothing is layered and loosely fitted. The inner layer, of caribou skin, is worn with the fur to the wearer's skin; a second, outer skin is worn with the fur outside. For footgear, Eskimos wear sealskin mukluks, which are loosely fitted, changed frequently, and discarded when it is no longer possible to chew them into pliability.
       
    Previous cold injury experience.- There seems no doubt that previous cold injury predisposes the soldier who has experienced it to further trauma from cold. The degree of predisposition varies in proportion to the severity of the original injury, recurrence being most frequent when the previous injury has been moderate to severe.
       
    It was thought that some of the cases of cold injury which occurred on Kiska were early recurrences of the injuries which had been sustained on Attu, though the possibility of recrudescence rather than recurrence could not, of course, be completely dismissed (p. 99) . In Italy and in Europe, however, there was no doubt of the seriousness of recurrent cold injury.
       
    Lt. Col. (later Col.) Fiorindo A. Simeone, who made a special investigation of trenclhfoot in the Mediterranean theater in the winter of 1943-44 and in the following winter (p.101), estimated that 15 percent of all casualties from this cause who were returned to duty might be expected to have recurrences. He also expressed the opinion that a man who had suffered a cold injury would be particularly susceptible to the effects of cold if he were exposed again within a few weeks or a few months. The course of events substantiated his opinion. Although only 2 percent of the personnel of all divisions of the Fifth U. S. Army suffered from trenchfoot, 18 percent of all patients hospitalized for this cause had previously been hospitalized for it. Twenty-two percent of the cases observed in December 1944 were instances of recurrence (8 percent from the winter of 1944-45 and 14 percent from the previous winter), and, in January


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1945, 23 percent of the cases were recurrent (18 percent from the winter of 1944-45 and 5 percent from the previous winter). The conclusion of Berson and Angelucci, that previous exposure is not an important factor in susceptibility to cold injury, is not in accord with the conclusions of others. The explanation probably is that their studies were made before the factor of previous exposure had begun to exert its heaviest influence.
       
    Recurrent trenchfoot in the European theater was first encountered in the Seventh U. S. Army, many of whose components had fought in Italy the previous winter. On 30 November 1944, an officer from the Preventive Medicine Division, Office of the Chief Surgeon, ETOUSA, noted in a memorandum on trenchfoot in the Third and Seventh U. S. Armies that, between 1 October and 18 November, 1,441 cases had been reported in the Seventh U. S. Army and that about 50 percent of these were instances of recurrence. The experienced divisions from which most of these recurrences came had few new cases except among Japanese-American troops. These troops had suffered heavily from this cause in Italy and had the same experience in France. Other estimates of recurrent trenchfoot in soldiers who had sustained cold injury in Italy the previous winter ranged from 30 to 35 percent.
       
    When investigators from the Office of the Chief Surgeon, ETOUSA, questioned the surgeons from various combat divisions concerning recurrent cases of trenchfoot and their opinion of the susceptibility to subsequent cold injury of those who had previously experienced it, it was the consensus that men with prior injuries were more susceptible to subsequent injury. The following endorsement forwarded by the Surgeon, 45th Infantry Division, to the Surgeon, Seventh U. S. Army, was based on the opinions of all surgeons in the division and was representative of the opinion in the whole theater:
      
     a. Trench foot in Italy, especially if of such a degree as to be classified as moderate, did render the men susceptible to vascular disturbances in the feet between the period of landing in Southern France and the onset of weather cold enough to actually precipitate trench foot.
    b. Persons who have had trench foot will not tolerate well intensive marching, even though the weather is warm.
 
    Incidentally, the surgeon of the 2d Infantry Division recorded that men who had suffered from frozen feet in Michigan during winter maneuvers 2 years earlier were the first to succumb to cold trauma in the 1944-45 campaign on the Western Front.
       
    The situation with respect to recurrence is excellently summed up in a report from the 23d General Hospital covering data from 5 November to 1 December 1944 and included in Essential Technical Medical Data, ETOUSA, for November 1944:
       
    Of 122 so-called recurrent cases, 58 patients had received previous hospital care for cold injury. They had spent a total of 3,788 days (10.3 years) in hospitals, and 749 additional days in reconditioning. Many of them had been returned to A (full) duty, and had remained on full duty for several weeks, but closer analysis showed their activities to have been of a limited nature. These men were really a burden to their commands because of frequent sick calls, the periods they spent in quarters, their constant complaints of foot pain on walking and in wet, cold weather, and the necessity of transporting them in vehicles when


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the troops advanced. Return to combat conditions frequently caused prompt relapses, especially in men who had sustained their first cold injuries in France. Patients with recurrent cold injury did not have a more severe grade of injury than those primarily affected, but their tolerance to wet and cold was definitely less.
 
    Medical officers responsible for the management of trenchfoot did not at first comprehend the ready susceptibility to subsequent cold injury of men who had previously sustained such injuries. They soon learned the lesson. In the winter of 1943-44, for instance, 50 percent of all men with trenchfoot treated at the 45th General Hospital in Italy were returned to full duty.9 In the second winter, when the risk of re traumatization by cold had become more clearly understood, only 2.1 percent were returned to full duty.
       
    Experiences in the European theater also showed that the usefulness to the Army of a man who had sustained a cold injury was likely to be limited. On 1 December 1944, the Commanding General, Third U. S. Army, wrote to the Theater Chief Surgeon that serious consideration must be given to the rapid replacement of able-bodied soldiers in the rear by men who had suffered from trenchfoot and who could do duty as military police or truck drivers or who could work in other posts in which they would not again be exposed to wet and cold.
       
    During the week ending 24 February 1945, the Office of the Surgeon, United Kingdom Base, surveyed one general hospital chosen at random from each of six hospital centers in respect to the trenchfoot situation. The disposition of the patients indicated that the lesson of recurrent cold injury had been learned. There had been 1,828 dispositions in a total of 3,769 admissions for cold injury in these six hospitals up to and including 21 February 1945. Of this number, 192 men had been returned to general duty (11 percent) ; 672 had been returned to limited duty (37 percent) ; 443 had been sent to convalescent hospitals (24 percent) ; and 520 had been evacuated to the Zone of Interior (28 percent) . In short, and assuming that the men returned to full duty had been able to stand up under it, which is a highly unlikely assumption, 89 percent of 1,828 combat troops had been lost from combat duty because of cold injury. The results were somewhat better in the hospitals which had stressed early, active exercise and had conducted special classes in rehabilitation.
     
    These dispositions were far from the optimistic predictions advanced early in the winter. In the 1944 report of the 108th General Hospital in Paris, in which 150 beds had been set aside for the investigation of cold injury, the estimate was that only 10 percent of the casualties from this cause would have severe enough injuries to require evacuation to the Zone of Interior and that 37 percent would have injuries mild enough to permit their return to duty within 60 to 90 days. As a matter of fact, about a third of all patients admitted with cold injury as the primary diagnosis had to be evacuated to the Zone of Interior and 18 percent received Certificate of Disability discharges.
       
    One reason why it was thought that recurrence would not be a factor of major importance in field forces on the Western Front was that the evacuation
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9 See footnote 8, p. 380.


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policy encouraged the removal to rear echelon medical installations of men with even mild injuries if their symptoms lasted more than 2 or 3 days.10 With a triage and evacuation policy of such strictness, opinions were expressed as late as January 1945 that recurrent trenchfoot would not be great in combat soldiers. Recurrence did take place, however, when many casualties originally evacuated with apparently mild injuries were returned to combat duty; the importance of previous cold injury as a host factor in the causation of this type of trauma thus was proved again.
       
    When the weather became warmer, many hospitals began to send larger proportions of their patients with cold injury back to full duty, or to limited duty, on the ground that they would not be exposed again to extreme cold or wet cold. This policy was also not successful. Men returned to even limited assignments did not usually hold up well under their duties, and many of them eventually had to be evacuated to the Zone of Interior.
       
    The evidence collected in Italy and in the European theater thus left no doubt that the wisest plan of disposition was to return all casualties with cold injuries, unless they were very mild (first degree), to the Zone of Interior for possible assignment to a theater where the climate was more moderate and their services could be better utilized. The loss of time was enormous when they were returned to full or even limited duty in a cold climate. It would have been wiser to retain in the theater in which they had sustained their injuries only those who had some special talent for the war effort. Even when this plan is followed, the residua of cold injury (p.284) will often make these soldiers a burden rather than an asset to their organizations.
       
    Because so many men with recurrent cold injuries lacked any objective evidence of the disease, their management was particularly difficult. When there was obvious tissue damage, the decision was simple, but no test was available by which physiologic disturbances could be demonstrated, and, in the absence of sound proof to the contrary, complaints had to be accepted at their face value. At that, malingering was suspected in a surprisingly small number of cases.11
       
    Inherent constitutional factors.- Lewis, in his discussion of chilblains and in his reports on cold in general (p. 235) , has shown that the individual response to cold varies greatly from person to person. This fact is generally accepted, though the inherent constitutional reasons for the variability are not readily apparent. The Raynaud and Buerger syndromes are well known and easily recognizable clinically, but the abnormal physiologic processes upon which they are based have not been satisfactorily explained. It is not at all clear why moderate cold should act as a trigger mechanism in one person, setting off the typical response to cold, including blanching and even blue coloration
____________
10 Minutes, Trenchfoot Conference, Office of the Chief Surgeon, ETOUSA, Paris, 24 Jan. 1945.
11 Another interesting feature of the report of the research team which studied cold injury in Korea during the winter of 1951-52 (p. 380) was its confirmation of the experiences in the Mediterranean and European theaters concerning the effects of previous cold injury. A previous injury was shown incontrovertibly to predispose to a second attack (p. 417). The attack rate among soldiers who had had no previous injuries was 2.6 per thousand, compared to 5.0 per thousand for men who had previously sustained cold injuries.


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of the skin, while in other persons under the same conditions of exposure sensitivity is very much less marked.
       
    Lange and his associates,12 who accept the thesis that sensitivity to cold varies widely from person to person, take the position that susceptibility is rather constant in the same subject. They subjected volunteers to spot-freezing, applying to an area 5 cm. in diameter a metal capsule at 3.6 º F (-15.8ºC) for 30 minutes. Exposures that consistently produced extensive gangrene in the total exposed area in some volunteers did not cause tissue breakdown in others, in spite of repeated tests. Lange and his group believe that by means of standard test procedures to be developed from investigations such as these it may be possible, eventually, to screen persons with an unusually high sensitivity to cold.
       
    German students of cold injury have repeatedly emphasized the importance of individual susceptibility to cold. Block,13 for instance, concluded that the vasomotor constitution of the particular soldier is the determining consideration and that asthenic types are most susceptible. Stucke 14 found that men who had followed indoor occupations were more susceptible to cold than those who followed outdoor occupations and that persons whom he described as vagotonics suffered most severely of all.
       
    Gohrbandt,15 who studied this phase of cold injury thoroughly, divided persons who suffer from cold into two groups, (1) those who show no overt residual signs after injury and (2) those who continue to show signs and symptoms, such as impaired circulation in the skin, low temperatures in the extremities, sensory disturbances, hyperhidrosis, and inadequate muscular response to exercise. Men in the latter group he regarded as constitutionally susceptible to cold and fit for military duty only in warmer climates. In his opinion, an army medical service should include a vascular center, one of the functions of which would be the differentiation of personnel who are susceptible to cold and those who are not. He did not consider that it would be practical for the unit medical officer to undertake this task.
       
    Gohrbandt regarded the vagotonic or bradycardic individual as extremely susceptible to cold. In this group, he placed all those with pulse rates of less than 68 per minute and those with any proneness to allergic spasms, dermatographia, and early fatigue. He regarded sticky sweating of the hands and feet as a commonly associated symptom. He also quoted Koch's dictum to the effect that cardiac vagotonics are potentially circulatory sympatheticotonics and suggested that men who answer this description should not be assigned to service in cold climates. This is a sound principle. Its development and
____________
12 Lange, K., Weiner, D., and Boyd, L. J.: Frostbite: Physiology, Pathology and Therapy. New England J. Med. 237:383-389, 11 Sept. 1947.
13 Block, W.: Die Bedeutung des Vegetativen Nervensystems beim Zustandekommen Õrtlicher Erfrierungen. [The Significance of the Autonomic Nervous System in Frostbite.] Arch. klin. Chir. 204: 64-83, 20 Dec. 1942. Abstract in Bull. War Med. 4: 268, January 1944.
14 Stucke, K.: Kãlteschãden and Erfrierungen in Felde. [Cold Injuries on Active Service.] Beitr. Kin. Chir. 174: 1-10, 30 Nov. 1942. Abstract in Bull. War Med. 4: 507, May 1944.
15 Gohrbandt, E.: Wiedereinsatz Frostgeschadigter. [The Return to Service of Soldiers who have Suffered from Frostbite.] Zbl. Chir. 70: 1584-1586, 30 Oct. 1943. Abstract in Bull. War Med. 5: 552, May 1945.


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practical application, however, await a better understanding of the physiologic abnormalities involved in susceptibility to cold and the development of simple specific tests along the lines of those proposed by Lange and his associates.
       
    Ian Aird, who abstracted Gohrbandt's article which has just been summarized, commented editorially on the more specific type of susceptibility to the local effects of cold (that is, hereditary cold fingers, chilblains, Raynaud's syndrome, and the conditions which give rise to them) and criticized him for not including them in his discussion. In Aird's own opinion, cold susceptibility can be detected on a moderately cold winter morning merely by inspecting the hands of the men who are drawn up on parade. This kind of testing is an obvious improvisation. It is no more capable of weeding out the persons who are less than grossly susceptible to cold than sick call inspection can identify a man with rheumatic heart disease who presents no gross physical signs.
       
    The captured German medical officers and noncommissioned medical officers who were interviewed in January 1945 in the European theater (p.204) consistently mentioned the constitutional makeup (that is, the state of the sympathetic and parasympathetic nervous systems) as a factor in cold injury. They also commonly expressed the opinion that age, previous cold injury, and the use of tobacco influenced individual susceptibility to cold injury. 16
       
    The theory has been advanced that persons who present cold agglutinins in the blood may be more susceptible to exposure to cold, and may present higher percentages of intravascular agglutination and ischemia as a result, than those in whom this finding is absent.17 On the basis of this theory, Loewenthal studied 24 patients with trenchfoot and obtained data which he interpreted as indicating that cold agglutinins were found more often in their blood and tissue fluids than in the blood and tissue fluids of the normal soldiers used as controls. Boland, Claiborne, and Parker,18 who also found a higher incidence of cold agglutinins in patients with trenchfoot than in normal controls, stated that these agglutinins were invariably present in the patients with gangrene who were included in their series. The significance of these observations remains to be elucidated.

    In a survey of 158 patients with trenchfoot on the surgical service at the United States Army General Hospital, Camp Butner, N. C., then serving as a trenchfoot center, it was observed that over 95 percent fell into the group of cases described by Gage 19 as vascular variants. These men had previous histories of hyperhidrosis, cold feet, nervousness, which sometimes seemed
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16 Observations of the research team which studied cold injury in Korea during the winter of 1951-52 indicated a negative correlation between the use of tobacco and frostbite. There was a highly significant difference in the use of tobacco among frostbite victims and their bunkermate controls, with the men with frostbite consuming far less tobacco than the nonfrostbitten controls. Possible psychiatric factors may explain this finding.

    The report of the team bore out to some extent Gohrbandt's theory that the bradycardic individual is particularly susceptible to frostbite. The mean pulse rate of cold injury casualties was 75.3 per minute compared to 86.8 per minute for controls.
17 Report, Lt. Col. Fiorindo A. Simeone, MC, to the Surgeon, Fifth U. S. Army, subject: Trenchfoot in the Italian Campaign 1943-45.
18 Boland, F. K., Claiborne, T. S., and Parker, F. P.: Trench Foot. Surgery 17: 564-571, April 1945.
19 Letter, Col. I. M. Gage, MC, Headquarters, Fourth Service Command, to Brig. Gen. Fred W. Rankin, Chief Consultant in Surgery, Office of the Surgeon General, 23 Mar. 1945.


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hereditary, and other evidence of sympathetic imbalance. They stated that they had developed cold injury under circumstances in which large numbers of their associates had not. A number of them presented marked dermatographia, with wide hyperemic flares along the pencil marks.
 
Preexisting Pedal Deformities, Infections, and Circulatory Abnormalities  

    In this same connection, Col. Charles B. Odom, MC, Consultant in Surgery, Office of the Surgeon, Headquarters, Third U. S. Army, noted that the number of deformities such as claw foot, hammertoes, and other pedal deformities was extremely high in patients with trenchfoot as compared to the rest of the hospital population. 20 He wondered how some of these men had ever been accepted in the infantry, and he had no doubt that when they sustained cold injury they were far worse off than men with normal feet. Other observers commented that men with circulatory deficiencies, flat feet, and other foot troubles were foot conscious, reported on sick call promptly, and therefore tended to have milder forms of cold injury. If, however, they could not obtain care, or if they were treated improperly, they presented a severer form of injury, after less exposure, than men without previous foot disabilities.
       
    In both the Mediterranean and the European theaters, there was a large amount of fungous infection of the feet. It caused a good deal of concern, particularly in the European theater, because of the potential loss of manpower to which it might lead. Investigation showed that the incidence was related to a number of factors, including poor foot hygiene, the type of duty assignment, the use of shoes with rubber soles, the use of extremely heavy British-issue socks in warm weather, variations in the care of showers, failure to use preliminary foot baths, and the use of previously worn hospital slippers which had not been sterilized. The control of these factors invariably reduced the incidence of fungous infection. There was no apparent connection, however, between previous fungous infection of the feet and the development of cold injury.
       
    An attempt to determine the possible relation of previous injury or disease to the occurrence of trenchfoot was undertaken in the Mediterranean theater but was not conclusive.21 A review of the histories of 144 patients with trench-foot who were admitted to a hospital in North Africa in the first winter of the Italian fighting showed no higher incidence of previous disease or injury than was found in a control series of 877 patients admitted to the same hospital for other causes. The distribution of possible etiologic factors, indeed, was strikingly similar in both series.

    Fifty patients with trenchfoot who were studied intensively in Italy in November 1943, soon after the epidemic nature of the condition was realized, were investigated from the standpoint of dorsalis pedis pulsations. These
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20 See footnote 10, p. 384.
21 See footnote 17, p. 386.


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pulsations were not palpable in 11 men after a week of hospitalization, which is very close to the proportion (25 percent) found absent in 125 casualties with trenchfoot studied later in another general hospital in Italy. The over-all frequency with which these pulsations cannot be palpated in men of this age group, while it is not known, is almost certainly not as high as 25 percent. In neither of these studies was it possible to distinguish cause from effect, and conclusions concerning the etiologic significance of these observations are not justified.
       
    A postwar study, by Silverman,22 of the dorsalis pedis and posterior tibial pulsations in 1,014 infantrymen revealed that one or both were absent in 13 percent, although absence of both pulsations on the same side occurred only five times in the entire series, and both pulsations were absent in both feet in only one case. The posterior tibial pulsation was more frequently absent in Negro subjects, and the dorsalis pedis in white subjects. Both arteries were found to show wide anatomic variations, and Silverman emphasized that these variations should always be taken into account before pulsations were reported to be absent. The material in this survey, the conditions of which were carefully controlled, seems comparable to that studied in the Mediterranean theater.
       
    In the Pacific, Col. I. Ridgeway Trimble, MC, consultant in surgery, felt strongly that men with circulatory anomalies of the lower limbs would be particularly susceptible to trenchfoot. He therefore made a serious, though unsuccessful, effort to have screening from this point of view made part of the preliminary physical examination (p.222).
       
    Physiologic processes.- While it is not within the scope of this volume to discuss the general physiologic processes involved in heat production in the body, or to describe the mechanisms of human-heat regulation, these functions cannot be entirely ignored. They are intimately related to the nutritional status of the host (p. 394), and lowering of efficiency or other alterations may account, in part, for the influence of recent infectious disease (p. 390) on cold susceptibility. When there is an excessive loss of body heat because of low environmental temperatures, the metabolic rate rises in an effort to maintain a balance between heat loss and heat production. The principal sources of the compensatory heat are the liver and the muscular tissues, especially those of the extremities. The mechanism involves increased tone of the skeletal muscles, involuntary muscle reactions, such as shivering, and the contraction of the smooth muscles of the skin which results in gooseflesh. All of these reactions consume energy and eventually produce fatigue. Some hemoconcentration also occurs, and there is probably an increase in the rate of circulation of the blood.
       
    Numerous observations have been made on the basal metabolic rate in relation to environment, though none of the studies is conclusive. It is generally believed that thyroid function is increased in cold climates, and there is
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22 Silverman, J. J.: The Incidence of Palpable Dorsalis Pedis and Posterior Tibial Pulsations in Soldiers. An Analysis of Over 1,000 Infantry Soldiers. Am. Heart J. 32: 82-87, July 1946.


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some evidence that oriental races and white men living under the same climatic conditions have different basal metabolic rates.23 White persons living in tropical climates appear to have reduced metabolic rates. By comparison, rates for Eskimos are higher. 

  Experiments have been carried out under the auspices of the Medical Research and Development Board, Office of the Surgeon General of the Army, to determine changes in thyroid activity in hypothermia by the use of tracer radioactive iodine. Lange, Gold, Weiner, and Kramer 24 conducted experiments on rabbits to observe the possible protective effect of thyroid administration against cold injury. Animals given thyroid in amounts sufficient to raise their basal metabolic rates between 30 and 50 percent had a reduced rate of loss of body heat and a decided prolongation of survival time, which could be increased by as much as 54 percent when the optimal dosage of thyroid was administered. Conversely, there was an increase in the rate of loss of body heat and a reduction of survival time, in comparison with normal controls, when thyroid function was suppressed by the administration of thiouracil. The protection afforded by thyroid administration Was not immediate. There was a timelag of 4 or 5 days after the drug was given before any protection against cold was discernible. These studies suggest that the level of the basal metabolic rate may serve as an index of susceptibility to cold, and also suggest that personnel with depressed or borderline rates may be unsuited for military service in cold climates. 

  Selye,25 who studied the protective physiologic mechanisms which come into play as a result of long-continued stress of various kinds, concluded, in general, that mild stress reactions may be beneficial but that reactions which are excessive or of long duration may give rise to diseases of adaptation. Cold is an agent of stress.
        
    The general adaptation syndrome may be subdivided into (1) the alarm reaction, which may be followed by shock phenomena, including hypothermia, hypotension, hemoconcentration, increased capillary permeability, and depression of the central nervous system; (2) the stage of resistance, which follows upon continued stress and the development of adaptation, characterized by enlargement of the adrenal cortex and increased secretion of cortical hormones; and (3) the stage of exhaustion, which occurs when the degree or duration of stress is such that adaptation fails and defenses are lost.
       
    The defense mechanism, Selye has pointed out, is intimately related to the activities of the hypophysis and the adrenal glands, the hormones of which play an important role in metabolism. In McFarland's studies (p. 393), which include the stress factor of fatigue, information is summarized on the relationship between fatigue and the excretion of the 17-ketosteroids. In
____________
23 Best, C. H., and Taylor, N. B.: The Physiological Basis of General Practice. 2d ed. Baltimore: Williams and Wilkins Co., 1950.
24 Lange, K., Gold, M. A., Weiner, D., and Kramer, M.: Factors Influencing Resistance to Cold Environments. Bull. U. S. Army M. Dept. 8: 849-859, November 1948.
25 Selye, H.: The General Adaptation Syndrome and the Diseases of Adaptation. Practitioner 163: 393-405, November 1949.


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extreme cases, this observer believes, there is a significant positive correlation. He also believes that further study of neuroendocrine changes would be valuable, since, if these reactions are a part of adaptation to all stresses, accurate and useful indexes of fatigue and other stresses might thus be determined. If McFarland's theory is correct, a promising avenue of approach to the cold problem would seem to be opened.
       
    The Medical Department Field Research Laboratory, as part of its investigation of the physiologic effects of cold, endeavored to determine the factors which control the secretion of the various endocrine organs under conditions of stress, including cold. It was found that hyperglycemia produced in experimental animals by orally administered glucose caused an increase in adrenal cholesterol and that an insulin-produced hypoglycemia caused a decrease. The results thus indicate, respectively, an inhibition and a stimulation of the adrenal cortex. Loss of cholesterol from the adrenal gland, which was observed in experimental animals exposed to low temperatures, was interpreted as evidence of decreased resistance. When aqueous adrenal cortical extract was administered to animals exposed to cold, it prevented the lowering of the adrenal cholesterol to the levels observed in control animals.
       
    The understanding of these various inherent constitutional factors is, at best, imperfect at this time, and further investigation along these lines is essential if military management of personnel under stress, including the stress of cold, is to reach an optimum level of effectiveness.
       
    Recent infectious disease. - Russian authorities, especially Ariev (p. 240), laid great stress upon recent infectious disease, in addition to wounding and other trauma, as a factor predisposing to cold injury. Their principal concern, however, was with severe frostbite, not trenchfoot. Neither the World War I nor the World War II experience with cold injury affords a basis for this point of view or for any other authoritative opinion concerning the influence of infectious disease on susceptibility to cold trauma. On the other hand, it is a reasonable assumption that the physical stress of an infectious disease would increase susceptibility to cold by lowering the efficiency of the circulatory system, reducing the local skin resistance to trauma, increasing fatigue, and, in general, decreasing physical fitness.
       
    Posture and dependency.- The position of the host has a decided influence on the incidence and severity of cold injury of the lower extremities. When Lange and his associates restricted the movements of rabbits during exposure to cold, they observed a decided decrease in survival time in the restricted animals as compared with that in animals exposed to the same conditions but left free to move about.
       
    Attention has already been called to so-called shelterleg, a type of injury similar to trenchfoot, which occurred in persons sleeping in deck chairs or on benches or boxes, with the lower extremities dependent, in the cool, damp air-raid shelters in London (p.9) . Dependency was also shown to be an important factor in immersion foot in surviving shipwrecked sailors, who had been compelled to sit or stand for several days in lifeboats or on rafts, with


391
 
little opportunity for movement and with their feet wet or in water. The records of frontline units afford many examples of the high incidence of cold injury among men pinned down by enemy fire and forced to remain sitting or squatting in wet, cold foxholes for long periods of time. There were also numerous excellent individual and small unit illustrations of men similarly pinned down who had moved their feet and legs sufficiently to ward off cold injury. In one instance, cold injury developed among all the men in one frontline unit except those who left the position daily to go after the rations.
       
    Fatigue. - The role of fatigue in the development of trenchfoot is difficult to isolate as an entity. Fatigue develops in proportion to the duration and intensity of stress. Similarly, the development of cold injury is related to the period of exposure. Time is a factor in both fatigue and cold injury, and periods of stress and exposure are likely to coincide. Fatigue is also inherent in exposure to cold, especially when loss of body heat and shivering are taken into consideration.
       
    For these various reasons, difficulties arise in the evaluation of the host factor of fatigue. Crude measurements can be made in terms of old and new troops, and by the comparison of the incidence of trenchfoot in troops in the line or in combat for a few days with the incidence in troops in line or in combat for many days. Wartime data do not provide good examples of any specific studies made to determine the influence of fatigue in the production of cold injury, and the general data available by units are not specific enough to permit correlation studies to demonstrate its effects. As in the matter of individual training, it is necessary to make assumptions and draw broad conclusions from circumstantial evidence alone.
       
    Fatigue is interpreted as meaning exhaustion of strength because of toil and weariness. It is mental and emotional as well as physical. It is important as a host factor in cold injury, if for no other reason than that soldiers, when they are fatigued, are less willing as well as less able to carry out such simple preventive measures as removing their shoes, putting on dry socks, massaging their feet, and exercising to restore the efficiency of the circulation in the lower extremities. Under circumstances of fatigue, discipline generally deteriorates, the deterioration including one of the key points in control of trenchfoot; namely, discipline of the individual soldier in carrying out measures for his own protection.
       
    Soldiers in the trenchfoot opinion survey to be described (p.400) were questioned about the number of days they had been without rest (table 16). Seventy percent of those with trenchfoot had been in combat 8 days or more before the onset of cold injury, and almost half (44 percent) of those who contracted it had fought for 15 days or more without rest. Details concerning the type of combat, periods of intense exposure, and other modifying factors are not available, but, if it can be assumed that they balanced out, it seems reasonable to infer from the data that fatigue, as expressed in days of actual combat, does influence the incidence of cold injury. The soldiers who did not contract cold injuries showed an almost identical distribution of combat days,


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TABLE 16.- Combat days without rest before onset of trenchfoot in 1,018 patients hospitalized in Zone of Interior 
 
but in this instance these men cannot serve as controls because fatigue may also predispose to injuries other than cold trauma.
       
    Fatigue is also an element in the differential between units that had good rotation of individuals and total units, as opposed to those that had no rotation policy and that required units and individuals to stay in the line for reasons of tactical expediency. This point is discussed in more detail elsewhere (p.446), but it may be said here that soldiers in combat are chronically fatigued and, that their fatigue is resolved only when they are brought out of the line and provided with facilities for rest. The difference between the incidence of cold injury in units in combat and in units in reserve is striking, as would be expected; but the presence or absence of other modifying factors, such as exposure, wet clothing, lack of shelter, inadequate food, and perhaps other considerations precludes more than generalized inferences concerning the host factor of fatigue. It all comes down to the fact, already pointed out, that under combat conditions fatigue was not evaluated and could not be evaluated in relation to cold injuries or to battle casualties in general. For that matter, the influence of fatigue upon nonbattle injuries, especially accidents, is not more than hinted at in the available records.

    Nonetheless, the influence of fatigue upon the incidence of cold injury can be roughly demonstrated by the following experience of three regiments of the 83d Infantry Division between 3 December and 27 December 1944.
       
    Unit case history No. 1.- This division left the United States in the spring of 1944, entered active combat in Normandy soon after D-day, and by early fall had fought across France into Luxembourg. During November, the division had a light static defensive assignment. On 3 December, the 330th Infantry Regiment was thrown into hard fighting in an active offense in the Hurtgen Forest. Four days later, on 7 December, the 331st Infantry Regiment entered upon the same type of combat. The 329th Infantry Regiment was not committed until 11 December. All three regiments fought in thickly wooded, hilly, muddy terrain. The weather was continuously cold and rainy, and the troops lived in foxholes, with little rotation possible because of the tactical situation.


393  

    In other words, there was no fundamental difference in the mission of any of these regiments, and all three experienced the same tactical and environmental conditions. The only differential of importance was the period of combat. The order of magnitude of trenchfoot experience in the three regiments was in rough proportion to the period of time each spent in combat. The highest incidence was in the 330th Infantry Regiment, which had the longest period of combat, and the lowest in the 329th, which had the shortest. In this respect, the 331st Infantry Regiment was intermediate (chart 8, table 17).
       
    A good deal of attention has been devoted to the effects of fatigue upon Air Force personnel and airline pilots and other operational personnel. McFarland's book on human factors in air-transport operations contains a review and critical analysis of the whole subject, as well as a summary of the general concepts of the nature of fatigue. Fatigue is discussed in relation to the operation of motor vehicles, and there is a special discussion of the temporary proneness to accidents observed among drivers of cross-country trucks after long hours at the wheel. Physical, mental, and emotional fatigue is defined, methods of measuring each of them are described, and acute fatigue and chronic fatigue are differentiated. Special stress is laid upon the fact that chronic fatigue is not relieved by short periods of rest and is therefore cumulative.
       
    Much of McFarland's work, as is clear from this brief resume, is directly applicable to many aspects of fatigue in combat ground forces. He did not, however, discuss the relation of fatigue to trauma, except trauma resulting from accidents, and further investigations and research in this field would be highly
 
CHART 8.- Cold injury in 3 regiments of the 33d Infantry Division, European theater, for weeks ending 10 November 1944 through 5 January 1945
 


394
 
TABLE 17.- Cold injury in. S regiments of the 83d Infantry Division, European theater, for weeks ending 10 November 1944 through 5 January 1945

profitable. He emphasized the need for further research on neuroendocrine mechanisms as part of the fatigue process and as part of emotional fatigue. Physiologic changes resulting from fatigue, particularly as they affect nervous tissue, blood vessels, and the susceptibility of tissue in general to trauma also require a great deal more study.
       
    Nutritional status.- Just as with fatigue, it is difficult to measure and assess the nutritional status of the individual soldier under combat conditions. Poor nutrition is undoubtedly a factor in the development of physical fatigue, and it may also influence the man's psychic responses in his reaction to the requirements for self-preservation. The nutritional status has a direct physiologic bearing upon the efficiency of the circulatory system and also upon the ability of local tissue to resist trauma and infection. Miller, 26 after studying groups of men living for periods of up to 10 days in extreme cold, with daily caloric intakes varying from no calories to 4,000 calories, noted a direct relationship between physical fitness and ability to rise to situations of stress. Men on low caloric intakes were inactive and responded with less serious effort to situations in which their survival was at stake. Failure to exercise in an effort to improve the circulation is part of the causation of cold injury, and failure to expend the necessary energy to change the shoes and socks and massage the feet is also a cause. In this study, both causes could be related to poor nutritional status combined with fatigue.
       
    It is not always a simple matter to provide troops in active combat with adequate rations. Inadequacies are often associated with the stress of hard fighting, and sometimes with long periods of inactivity. During rapid motorized advances, or when forces are pinned down in static positions and are largely
____________
26 See footnote 4, p. 379.


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cut off by the enemy, sufficient rations often cannot reach the frontline. Then men must subsist on emergency rations for periods well in excess of those for which these rations were intended. In these situations, it is conceivable that mild degrees of dehydration, as well as subclinical vitamin and protein deficiencies, will occur and may be sufficient to affect the general host susceptibility to cold injury.
       
    No specific studies on these points were carried out during World War II, and a survey of unit histories does not reveal any circumstances in which nutrition appeared to be the only variable in the factors productive of cold trauma. A number of tactical situations were recorded, however, in which troops of battalion or regimental size were cut off by enemy action for periods varying from a few days to a few weeks, in circumstances in which poor nutrition undoubtedly was an important consideration in the causation of cold injury. At the same time, cold and wet, and a number of modifying factors such as exposure, lack of shelter, immobility, intense combat, fatigue, and emotional stress also came into play. It is therefore not possible to evaluate the factor of nutritional status accurately by the method of unit study.
       
    It is nonetheless interesting in this connection, despite the limitation ofmany variables, to analyze the cold injury experience of the 8th Infantry Division, which was virtually isolated for a period of 2 weeks (chart 9, table 18).
       
    Unit case history No. 2.- This division arrived in Ireland from the UnitedStates in December 1943. It crossed to the Continent early in July 1944, and by late October had fought across France to Luxembourg. By this time it
 
CHART 9.- Cold injury in S regiments of the 8th Infantry Division, European theater, forweeks ending 17 November 1944 through 9 February 1945
 


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TABLE 18.- Cold injury in 3 regiments of the 8th Infantry Division, European theater, for weeks ending 17 November 1944 through 9 February 1945
 
had become an experienced combat division. From 1 November to 20 November inclusive, it fought a defensive action in Luxembourg on a 30-mile front, over a terrain which was hilly and rugged but which was relatively dry except for the muddy lowlands. During this period, the weather was moderately cold and there was considerable rainfall, but the troops had fairly satisfactory shelter. Rotation was good, and each man had two hot meals daily. Trench-foot incidence did not exceed 25 cases per week.
 
   On 21 November, the troops were moved to the Hürtgen Forest. Here, between 23 November and 6 December inclusive, they fought an active offensive action. The terrain was wooded and flat. The weather was moderate, but there was considerable rainfall, and the ground, which was poorly drained, became extremely muddy. An upsurge of cold injuries occurred late in November and in the first few days of December (chart 9, table 18), predominantly in the 121st Infantry Regiment. The incidence was not exorbitant and could be accounted for by heavy offensive action.
       
    The type of combat action changed on 7 December, and from that time until 25 December the division made limited attacks in the same area to clean out towns. It also conducted sporadic, intermittent offensive actions. On 8 December, the 28th Infantry Regiment was almost completely cut off in the Hürtgen Forest and could not be relieved until 23 December. During this period, the men were isolated and were almost continuously pinned down by enemy fire. Supplies had to be delivered through a long, narrow corridor and could be brought forward only at night. The type of ration provided is not


397  

stated in the regimental and divisional records, but circumstances such as these usually meant that K-rations had to be used. Hot food and facilities for heating food could not have been made available.
       
    Before the period of isolation, this regiment had had less than 25 cases of cold injury a week. With isolation, there was an immediate and dramatic rise in incidence, there being 86 cases the first week of isolation and 89 cases the second. Almost as soon as the regiment had been relieved, the incidence fell to 15 cases per week, or fewer, and did not rise above this level for the next 7 weeks. Thereafter, except for 25 cases recorded for the week ending on 2 March 1945, cases per week did not exceed 8 during the time that cold injury was prevalent.
       
    This was not a simple situation. Many variables were involved. The combat action was severe. Rotation was impossible. Shelter was limited to wet, muddy foxholes. All of these circumstances are conducive to cold injury. On the other hand, this was an experienced, battlewise unit. It had acquitted itself well in other engagements of equal intensity, in which it had had no undue incidence of cold injury. The principal difference in the situation described was isolation, which always greatly complicates the problem of providing adequate food for troops, while at the same time it increases exposure and decreases the effectiveness of triage and medical care. It can fairly be said, therefore, that inadequate nutrition was apparently a factor in bringing about an increased incidence of cold injury in this experienced unit during a period of isolation.
       
    Psychosocial factors.- At the beginning of World War II, the status of knowledge of psychosocial factors and of the possibilities of influencing them through preventive psychiatry was not such as to permit an attack upon them with any confidence. These are crucial elements in the effectiveness of combat personnel. They encompass the total range of physical, mental, and emotional stress; battle casualties; nonbattle injuries; combat exhaustion; and neuropsychiatric disability in addition to cold injury. Their efficient analysis would require the combined efforts of qualified psychiatrists, psychologists, and sociologists, as well as of competent military leaders.
       
    It is necessary, in spite of these lacks and requirements, to fill in the general background of the psychic effects of stress in order to appreciate how the addition of further stress, in the form of wet and cold, could intensify the situation. The data collected in World War II provide no means of measuring accurately the psychosocial host factor. It can be thought of only as a part of the over-all host factor of stress and as a component in the total causation of cold injury.
       
    The cost of neuropsychiatric casualties, together with the concept that men wear out in combat, just as a truck wears out under continuous use, was not fully appreciated in the early phases of World War II by any medical officers, including psychiatrists. Later, both in Italy and on the Western Front, the value of psychiatric advice and consultation as a preventive measure was much more widely appreciated, and psychiatrists were assigned as far forward as


398
 
divisions. There were many times, however, when the tactical situation made the application of optimum psychiatric procedures impossible, and the effectiveness of these measures also showed unit variations. As a result, rates for psychiatric casualties remained high throughout the war, especially during periods when combat action was severe and protracted. Of all combat branches, the infantry is exposed to the greatest danger of trauma. An analysis of attrition and replacement in the Fifth U. S. Army during its operations in North Africa 27 revealed that, by the time a regiment had been in combat 120 days, 50 percent of the original strength of its rifle battalions had been killed, wounded, or captured or was missing in action. The percentage would have been higher except for the removal of men from combat for illness or noncombat trauma. Neuropsychiatric rates of 1,200 and 1,500 per 1,000 per year were recorded in many rifle battalions, in comparison with rates of 30 or less in units of similar size in other branches of service.
       
    Fifteen to twenty percent of the total nonfatal combat losses sustained during severe combat in World War II were usually found to be neuropsychiatric, the proportion depending upon the intensity and duration of continued combat. Limits of endurance for the average soldier were found to range between 200 and 240 regimental combat days. Soldiers who received psychiatric care at the end of 200 combat days or earlier could usually be returned to combat duty. Men treated later were, as a rule, permanently lost as combat personnel. The British in Italy expected to obtain service of approximately 400 combat days per rifleman, but their policy was to relieve frontline riflemen after a period of 12 days or less, for rest periods of 4 days. American troops in the same theater, in contrast, were often in combat up to 40 days without relief, and sometimes fought as long as 80 days. Another point to be noted is that the men who were kept in combat for the longest periods were the indispensable, competent, well-tried, frontline soldiers, such as company or platoon officers, noncommissioned officers, squad leaders, and key enlisted men. When these men did break from stress, they were likely to be irretrievably lost to the combat forces, and they were always difficult to replace.
       
    Although motivation is a basic consideration, it is difficult to say precisely what role it plays in the production of trenchfoot. In the Mediterraneantheater, for instance, when cold injury first appeared in the winter of 1943-44, the willingness of troops to endure conflict was on the decline. They had begun to feel that they were being kept in the line for too long periods, without provision for sufficient rest, and this feeling may well have influenced them in their lack of effort to protect themselves or, more correctly, influenced those of them who, at this time, had the means and knowledge to protect themselves.
       
    An analysis of motivation in the second winter in Italy is still more difficult. Favoring deterioration were two factors, continued and very heavy combat, especially during the capture of Rome and the piercing of the Gothic Line, and the mere passage of time. There were, however, other factors operating to
____________
27 Letter, Brig. Gen. R. B. Lovett, Adjutant General, ETOUSA, to Commanding Generals of Major Commands, 4 Oct. 1944, subject: Prevention of Loss of Manpower from Psychiatric Disorders, enclosure thereto.


399
 
sustain morale. Although fighting was sometimes heavy, there was relative tactical inactivity during a large part of the winter. Many preventive and protective practices had been instituted, including the rotation of troops through rest areas, correction of many of the former discriminations against combat troops, especially when they were on leave in base areas, and the belated attempt to glorify the role of the combat soldier by such means as extra pay and the award of the Combat Infantryman's Badge. It is not possible to say, however, whether the decrease in trenchfoot during the second Italian winter was in any way influenced by a greater desire on the part of the men to protect themselves against cold injury than they had displayed during the first winter.
       
    It is a curious fact that in the European theater, when trenchfoot rates were high, rates for neuropsychiatric disorders were reduced. The immediate explanation would seem to be that potential neuropsychiatric casualties found medical evaluation for mild cold injury an honorable as well as a convenient way to avoid combat, and that their number was large enough to affect the rates for these conditions. Such a course was undoubtedly taken by some soldiers. There were, however, other considerations. The soldier was often faced with an actual choice between severe injury or death on the one hand and acquiring trenchfoot by remaining immobile in his foxhole, on the other. He usually remained immobile. The fact that large numbers of men with bona fide trenchfoot were evacuated from combat units before they might be expected to become neuropsychiatric casualties would seem, automatically, to establish the relation noted between trenchfoot and neuropsychiatric disorders.
       
    Intelligence and morale are both components of the group of psychosocial factors. Intelligence enters into the host complex, in that the intelligent soldier is more easily trained and more readily understands the necessity for the maintenance of fitness. Morale is an intangible state of mind and emotion that is difficult to elucidate. Moreover, the morale of the individual soldier, which is a host factor, cannot be disassociated from unit morale, which is a complex of leadership, motivation, confidence, and the state of discipline and training. Units in which the morale of the individual soldier was high always had less cold injury for the same reasons that they had lower rates for venereal disease, fewer courts-martial, and a minimum of accidents.
     
    Psychiatrists and military leaders alike came to consider motivation in the individual soldier important in his ability to withstand stress of all kinds. It could be shown that an incentive beyond the urge for self-preservation and the desire to maintain self-respect was necessary for the soldier. The psychiatrists believed that rewards should be given for achievement. They also advocated tactical and strategic orientation of troops, individually and by groups, as broad as was consonant with security. The wisdom of this concept was amply demonstrated by the performance of such outstanding combat units as the 3d Infantry Division, whose combat missions were arduous and difficult over a period of more than 3 years. Considering the type of combat in which this division was engaged, it could have been expected that its rates for cold injury would sometimes be high; the over-all record, however, was excellent.


400  

    About all that can be said in summarizing the influence of psychosocial host factors is that many of them are intangibles not susceptible of precise measurement and that the war experience provided unfortunately little data concerning their true importance. No apparent sharp line separates the effects of physical stress, emotional stress, and mental stress. There is considerable reason to believe that there may be an organic approach to many of these psychiatric problems. It may be that the same neuroendocrine influences that now seem to condition fatigue are also components of the associated emotional reactions to stress. Be this as it may, the situation further indicates the need for additional study and research and for the evaluation of men as a whole rather than the mere collection of data dealing with individual facets of the behavior and physical responses of the individual. Much, in short, remains to be learned concerning the prevention of the cumulative effects of stress upon the individual host.
       
    Training.- The effectiveness of a unit in combat depends upon training. The life of the individual soldier also depends upon it. In the military sense, training is a term of broad significance. It includes education, indoctrination, and motivation of the individual soldier, and the teaching of combat techniques to military units. The incidence of cold injuries varies greatly between experienced, well-trained units and inexperienced organizations not so well versed in the art and techniques of combat.
       
    Training must therefore logically be considered both as an environmental and as a host factor. As a host factor, it concerns the hardening of the individual soldier. In this sense, it might also be interpreted broadly to include acclimatization and the necessary physiologic adjustments required to develop a good combat soldier in excellent physical condition.
       
    At the same time, training involves a series of intangible human factors such as self-discipline, morale, intelligence, character, and habits of self-preservation. Training, in the present discussion and also later, when it is discussed as a social-environmental factor (p.442), must be interpreted as including experience, because it is impossible to differentiate successfully between the influence of training as an educational process and the influence of experience as a teacher in the hard school of combat.

    Opinion survey.- In the spring of 1945, the Preventive Medicine Service, Office of the Surgeon General, in conjunction with the Information and Education Division, Army Service Forces, undertook a survey of soldiers returned from overseas with trenchfoot.28 The survey was designed to evaluate many factors, including host factors, to study men's attitudes and behavior, and to determine, as far as could be determined, why they had contracted cold injury.

    The investigation covered 1,018 enlisted men who had become casualties from cold injury. The 234 controls, who were selected from a total of 600 men hospitalized at the same time for causes other than trenchfoot, were chosenbecause the conditions of their combat service were comparable to those sus-
____________
28 Report No. C-114, Information and Education Division, Army Service Forces, 2 June 1945, subject: Trenchfoot Survey.


401

tamed by the men who had acquired trenchfoot. Both groups represented many units. Some had fought in Italy and others in the European theater during the winter season. Certain inferences can be drawn from the responses of both groups about the amount of instruction they had received concerning cold injury and about their knowledge of, and concern in, its prevention.

    The report, made 21 June 1945, showed that only 55 percent of the men who contracted trenchfoot had heard about it before going into combat, whereas 79 percent of those who did not contract it had knowledge of it. Only 37 percent of the men with trenchfoot said that their officers or noncommissioned officers had told them how to prevent it; 71 percent of the men who did not contract it had had this type of training. Only 26 percent of the men with trenchfoot had given some thought to their chances of acquiring cold injury under winter combat conditions, while nearly twice as many (49 percent) of the men who did not contract it had considered the possibility. Queries concerning the opinion of the two groups about the amount of training they had received on certain items before they went into combat elicited variable replies (table 19).

    No definitive conclusions can be drawn from these data. On the other hand, after the merits and fallacies of opinion surveys in general have been taken into consideration, the inference is permissible that the training the soldiers had received varied from individual to individual, and that those who had had the least training in cold injury prevention, and who had been the least interested in it. were chiefly the men who acquired the injury.
 
TABLE 19.- Opinion on training in trenchfoot prevention of 1,018 patients with trenchfoot and 234 patients with other injuries hospitalized in Zone of Interior 1
 
    A further example of the role of individual training in the causation of trenchfoot is illustrated by the experience of replacements (reinforcements) in combat units as compared with the experience of older, better trained, more battlewise soldiers. The official records of trenchfoot incidence do not differentiate between replacement or veteran status, but unit records and sanitary and other reports of unit sick contain numerous comments concerning the inadequate training status of replacements. The investigators from the Office of the Chief Surgeon, ETOUSA, who studied trenchfoot in several armies, division by division, consistently recorded similar observations. Some replacement troops acquired trenchfoot en route to frontline units from replacement centers. Trenchfoot occurred in one unit, the 89th Infantry Division, while it was still


402

CHART 10.- Cold injury in 3 regiments of the 95th Infantry Division, European theater, 8 November through 21 Decembeer 1944

in a replacement center. It was universally recognized that the incidence of cold injury among replacements was much higher in their first weeks of combat than it was for experienced soldiers.
       
    It is only fair to add that this situation cannot be attributed entirely to defects in training. Many times, soldiers who had been properly trained failed to appreciate the importance of the training they had had and consequently failed to apply what they had been taught, or were unable, because of the combat situation, to apply their knowledge.
       
    The reverse of this situation is demonstrated by the experiences of old and tried units in which all the factors relating to trenchfoot or cold injury, including the individual training of the soldier, were good.
       
    Unit case history No. 3.- The 95th Infantry Division 29 is an excellent example of what has just been said (chart 10, table 20). This division was on the offense during November and part of December. It made at least three river crossings, and it assisted in the reduction of the Metz fortresses. Yet at no time during this whole period was its incidence of trenchfoot high. The maximum number of cases on a single day never exceeded 35, and on only one other day did the number reach 30. It is interesting that during this period replacements for casualties of all types were slow in being brought forward, which means that the men at risk were for the most part well trained and experienced.

  The excellent record of this division of course involves many other factors, but there can be little doubt that the good status of training of the individual soldier was one important reason for the low incidence of cold injury. In this  
____________
20  Further details of the experience of this division are presented on p. 426 (unit case history No. 10).


403
 
TABLE 20.- Cold injury in 3 regiments of the 95th Infantry Division, European Theater, 8 November through 21 December 1944
  


404
 
division, as in others, though the evidence in favor of training as a positive modifying factor in cold injury is largely circumstantial and corroborative, it is nevertheless indicative of the significance of this special factor, which deserves more careful evaluation in the future. <> 

Environmental Factors
       
    Environment is the medium through which agent and host are brought into contact and interact to produce cold injury. Elements providing the mechanism through which cold injury takes place are chiefly environmental. Physical environmental factors include temperature, altitude, precipitation, wind, thawing, terrain, and shelter. Socioeconomic environmental factors include leadership, medical care, type of combat action, rotation policies and practices, and certain elements of training and discipline.

    The biologic environment, which is so important in many mass diseases, has little or no relation to cold trauma. Cold, or cold and wet in combination, are the specific cause of cold injury in the same sense that a species of Streptococcus is the specific cause of puerperal fever or that Bacillus typhi is the specific cause of typhoid fever. The mechanisms through which the agent may act upon the host (man) are widely various. The typhoid baccillus may affect the host through the accidental drinking of contaminated water, the family use of milk containing typhoid bacilli, or the consumption at a church or other large supper of food made dangerous by the typhoid carrier who prepared it. The mechanisms which produce cold injury are much more varied and encompass a greater range of environmental variables. They may extend from a low, muddy terrain, coupled with severe combat, at one extreme, to lack of individual leadership during a simple static defense on the other.
 
Physical Environmental Factors
 
    Weather.- Climate may be defined as the average weather of a given place or region. Weather is interpreted to mean the interaction of meteorologic components, including temperature, moisture, precipitation, wind, and similar factors, at a given time. Each of the more important of these factors must be analyzed separately if the total influence of weather as an environmental factor in the production of cold injury is to be fully understood.
       
    Temperature.- Cold has been incriminated as the primary causative agent of cold injury, and basically this is a fact, but temperature, as it fluctuates by time periods and as it is associated with other modifying factors, chiefly determines the incidence and severity of this type of injury. This has been true in all recorded wars. It was true in the Mediterranean theater in World War II. It was equally true in the European theater (charts 11, 12, 13, and 14, and tables 21 and 22) .


405  

CHART 11.- Cold injury cases, mean temperature, and precipitation, First U. S. Army, European theater, November and December 1944
 
     From 1 November through 20 December 1944, the mean daily temperature on the Western Front was about 40° F. (4.4° C.). Only infrequently during this period did minimal temperatures fall below freezing. Then, just before Christmas, a cold wave covered the whole area of the front, and daily mean temperatures were below or only slightly above freezing until the end of January.
       
    It is not always possible to demonstrate that temperature per se has directly influenced the incidence of trenchfoot. Examination of the records of several divisions shows periods of high incidence of trenchfoot at times during the winter of 1944-45 when the mean daily temperature was relatively constant in the range from a little below to a little above 40°F. (4.4° C.). One explanation is that trenchfoot does not manifest itself immediately upon exposure. There is a definite incubation or lag period, of 3 days or more on the average, between the beginning of exposure and the appearance of the injury. As long as the temperature is below 50° F. (10° C.), trenchfoot is likely to occur, its development depending upon the presence or absence of other influencing factors, especially the synergistic factor of wet. To state it more simply, the appearance of trenchfoot depends chiefly upon factors that enhance loss of body heat rather than upon low temperature per se. In fact, as the brief


406
 
CHART 12.- Cold injury cases, mean temperature, and precipitation, First U. S. Army, European theater, January and February 1915
 
Pacific experience showed (p. 211), a form of cold injury can occur, if modifying factors are favorable, when temperatures are high. On the other hand, frostbite is closely related to temperature. It manifests itself almost immediately when the temperature falls below freezing. The incubation period, although dependent upon the duration of exposure, may be only a few minutes if the temperature is very low, and not more than a few hours if it is just below the freezing point.
       
    The first major outbreak of trenchfoot on the Western Front in World War II reached its peak during the week ending on 17 November 1944 and continued into the first days of December. During this period, in which no frostbite was observed, temperatures varied from just below 40° F. (4.4° C.) to just above 50° F. (10° C.). Precipitation was unseasonably heavy at this time, and violent offensive fighting was in progress. Therefore, except for the fact that the average temperatures were within the accepted trenchfoot range, temperature as an environmental factor does not seem to have had a great deal to do with this epidemic of cold injury.
       
    On the other hand, the epidemic which began the first days of January 1945 and reached its peak during the week ending on 19 January 1945 consisted of a relatively high proportion of frostbite cases. The incidence, which


407
 
CHART 13.- Cold injury cases, mean temperature, and precipitation, Third U. S. Army European theater, November and December 1944
 
continued high all through January, apparently was directly contingent upon the temperature, which during this entire period was seldom above the freezing point.
       
    Early in February 1945, frostbite practically disappeared. Then a thaw occurred, and the element of wet again became prominent. As a result, the cold injury curve, which had included a relatively large proportion of frostbite cases during the preceding weeks, leveled off from its downswing during the week ending on 9 February 1945, principally as the result of an increase in trenchfoot at this time (chart 15, table 23).
       
    The combat experience of the 30th Infantry Division clearly illustrates the relation between cold and trenchfoot on the one hand and cold and frostbite on the other.
       
    Unit case history No. 4.- Between 1 November and 15 November 1944, the 30th Infantry Division was in a holding action and on active defense near Aachen, in Germany. From 16 November through 12 December, it was engaged in an attack toward the Roer River. On 17 December it moved to Belgium, and from that date until 12 January 1945 it was in defense near Malmedy. The defense was active, with occasional local offensive action in favorable terrain, though little shelter was available. During all this time the cold injury record of the division was good (chart 16, table 24).


408
 
CHART 14.- Cold injury cases, mean temperature, and precipitation, Third U. S. Army, European theater, January and February 1945  

    On 13 January 1945, the division was committed to an offensive action in the Malmédy-Saint-Vith area, in deep snow. Exposure to cold was severe because of lack of shelter. For the week ending on 19 January (that is, during the first 6 days of the offensive), the total cold injuries for all three regiments took a sudden and dramatic upswing and reached a peak for the whole winter. By far the largest component of this outbreak was frostbite, as cane be determined when the regimental curves for trenchfoot alone during the 2-week period are followed. During the week ending on 26 January, the outbreak became less intense, presumably because exposure was less, and, after 29 January, the curve leveled off as all units within the division were moved to an assembly area, where they were housed in villages.
       
    The increase in the tenor of combat action undoubtedly played a considerable part in the upsurge of cold injuries during the 2-week period just described. Intense combat alone, however, was not responsible. This unit had been in active combat before this time and had suffered no undue increase in cold trauma. During the earlier period of combat, the temperatures had been milder. The principal differentiating factor in the later period was exposure to low temperatures under conditions in which shelter was not available and which did not offer sufficient opportunity to rotate individual soldiers or small units to rest or warming areas.


409
 
TABLE 21.- Mean temperature, precipitation, and cold injury cases in the First U. S. Army, European theater, 1 November 1944 through 28 February 1945

    It has been pointed out already that cold injury has been known to occur at temperatures as high as 60° to 70°F. (15.6° to 21.1° C.) when there is long and constant exposure to wetness (p.211). At the other extreme are frostbite, which occurs with relatively short periods of exposure at freezing temperatures and just below, and sudden freezing of the tissues, which occurs with exposure to even lower temperatures. These facts suggest that cold injury must be acquired with progressively less exposure at progressively lower temperatures. To demonstrate this principle, carefully controlled experiments would be necessary within the range of temperatures in which military operations have been carried out in winter. Experiments of this kind have not yet been conducted.

    That low temperature is an extremely important factor in cold injury is borne out by the fact that in all divisions, young and old, experienced and


410
 
TABLE 22.- Mean temperature, precipitation, and cold injury cases in the Third U. S. Army, European theater, 1 November 1944 through 28 February 1945
 
inexperienced, and with good control policies and procedures as well as less satisfactory ones, the cold injury incidence rose on the Western Front during the periods of extreme cold between the last week of December 1944 and the first day of February 1945. Modifying factors generally balance out and leave low temperature as the dominant explanation for what happened.
       
    Precipitation.- Wetness, which has its source in precipitation, is a part of the agent complex in cold injury. When it is associated with cold, wetness greatly increases the incidence of cold injury. Precipitation is an environmental factor; that is, it is a component of many of the mechanisms which result in cold injury. The environmental role of terrain is extremely important from the standpoint of precipitation. It may be of such a nature as to cause a rapid runoff of precipitation, which is then less conducive to cold injury. If drainage is poor, on the other hand, the water table is high, mud or flooding results, and precipitation is then more conducive to cold injury.


411
 
TABLE 23.- Cold injury admissions and rates for the First, Third, Seventh, Ninth, and Fifteenth U. S. Armies, European theater, for weeks ending 3 November 1944 through 27 April 1945  

     Baron Larrey was the first to observe the association between precipitation and temperatures above the freezing point in the production of cold injury (p.31), but the full significance of this factor was not appreciated until the British experience in World War I. In 1915, Smith, Ritchie, and Dawson (p.241) first demonstrated the role of wet, and thus of precipitation, by animal experiments in which one group of rabbits had dry footing and the other was kept in cages with muddy bottoms. The incidence of cold injury in the second group was significantly higher than in the animals which had been subjected only to cold.
       
    Precipitation sets the stage for cold injury because it forms mud, floods valleys, raises streams, and causes the ground water table to rise to such a point that foxholes and trenches become damp, muddy, or partly filled with


412
 
CHART 15.- Total cold injury incidence rates for the First, Third, Seventh, Ninth, and Fifteenth U. S. Armies, European theater, for weeks ending 3 November 1944 through 27 April 1945
 
CHART 16.- Cold injury in 3 regiments of the 30th Infantry Division, European theater, for weeks ending 3 November 1944 through 16 February 1945


413  

TABLE 24.- Cold injury in 3 regiments of the 30th Infantry Division, European theater for weeks ending 3 November 1944 through 16 February 1945
 
water. Precipitation in the form of snow or sleet may encourage the development of frostbite, and melting snow acts to produce trenchfoot in the same manner as water from any other source.

    In 1944, the unusually heavy precipitation during the autumn and early winter was chiefly responsible for the first epidemic of cold injury (trenchfoot) on the Western Front. This epidemic reached its height in mid-November. Heavier rainfall in that army area was the chief reason why this epidemic assumed greater proportions in the Third U. S. Army than in the First. In the Third U. S. Army, trenchfoot took the form of a sudden, far-reaching point epidemic. In the First U. S. Army, the buildup was slower and the peak was lower. Terrain was also an important consideration in the Third U. S. Army incidence; its predominant features were streams, valleys, and low-lying land.
       
    Thawing.- Thawing of snow, sleet, ice, and frozen ground brings about wet and mud. Wet and mud, in combination with the temperatures at which thawing occurs, provide conditions ideal for the development of trenchfoot. Thawing is thus an environmental factor favoring trenchfoot in combination with both temperature and wet. If it occurs during the day, when temperatures are maximal, and is combined with freezing during the night, when they


414

CHART 17.- Trenchfoot and frostbite in 3 regiments of the 9th Infantry Division, Europeantheater, for weeks ending 3 November 1944 through 16 March 1945

are minimal, it may give rise to both trenchfoot and frostbite in troops subjected to these environmental conditions.
       
    Data for the Western Front support these observations. A general thaw began on 31 January 1945 and extended along the whole length of the front. The last of the big theaterwide epidemics of cold injury had begun on 5 January (chart 15) and was to continue until 23 February. The epidemic reached its peak during the week ending on 19 January and then began a rather precipitous downswing. With the onset of the thaw which began on 31 January, the curve abruptly leveled off for the week ending on 9 February and did not resume its precipitous downward trend until the following week. During the week ending on 2 February, the predominant cold injury was frostbite. During the week ending on 9 February, trenchfoot was theaterwide, because of the wet and mud produced by the thaw which began on 31 January.
       
    The experience of the 9th Infantry Division during this period was typical.

    Unit case history No. 5.-This division after previous operations in Africa and Sicily had been in combat action continuously on the Continent from 4 days after the initial Allied landings in Normandy. It was thus a battle-tried division, of great experience, with a good record for both combat and cold injury. At no time before the last few days of January 1945 (chart 17, table 25) had cold injury been a very important cause of loss of personnel, although the division had seen heavy combat under conditions favoring trench-foot and had had only short alternating periods of defense or reserve.


415  

TABLE 25.- Cold injury in 3 regiments of the 9th Infantry Division, European theater, for weeksending 3 November 1944 through 16 March 1945  
    In the period immediately preceding the 31 January thaw, operations were in the Monschau area. This is high, rolling, and forested country. The weather was moderately cold to cold. The ground was frozen and was covered by 12 to 18 inches of snow. The action was static def enst-. On 29 January, the division jumped off in an attack in deep snow. The weather was still cold, but there was alternating freezing by night and than ing by day. On the first day of the attack, the snow was dry, and frostbite was the predominant cold injury. By 6 February, the thaw had become general. By 10 February, the snow had, for the most part, melted, so that streams were swollen, and fields, forests, and roads were deep in mud. Chart 17 shows the trenchfoot and frostbite experience of the three regiments of the 9th Infantry Division and demonstrates the effect of alternate freezing and thawing in the production of both forms of cold injury, as well as the high incidence of trenchfoot during a period when precipitation was absent or light.
       
    The ratio of trenchfoot to frostbite in the 60th Infantry Regiment was diametrically opposite to that in the 47th (chart 17) . The 60th Infantry was operating in the worst terrain of the Monschau woods during the week ending


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2 February; alternate thawing and freezing had exposed this regiment to considerable wet in comparison with the other two regiments in the division, a fact which partly explains the higher trenchfoot incidence in the 60th. In addition, this regiment made three successive marches in low terrain in which exposure was great and during which there was limited time for the individual care of the feet. The 47th Infantry, on the other hand, made a long march in the snow in higher terrain, immediately following which it was thrown into repeated attacks before the objective could be reached. Men were fatigued and had little opportunity to care for their feet. Again, alternate thawing and freezing is the explanation, with trenchfoot by day and frostbite by night in tired soldiers who, because of the tactical situation, were unduly exposed to cold at night and were unable to obtain rest. Immediately after this experience, the division went on to the Roer River, which was crossed about 1 March. The Erft Canal was crossed shortly afterward. As a result, wet feet produced another rise in the trenchfoot incidence.
       
    Thus, thawing, by introducing the element of wetness, is an important environmental factor in the production of cold injury. At the same time, conditions are ideal for frostbite if soldiers who are subjected to thawing during the day must operate by night or are exposed by night to minimal, below-freezing temperatures, without adequate shelter.
       
    Wind.- Though it is an established fact that exposure to wind hastens loss of body heat, efforts to measure the degree to which the loss is brought about by winds of various velocities have been chiefly carried out in extreme temperatures in the Arctics. Siple (cited by Court 30), in 1939, was the first to use the excellent descriptive term "wind chill" to imply the combined cooling effect of moving air and low temperature. On the basis of observations made in the Antarctic in 1940, he developed a formula to describe wind chill and its fluctuations according to temperature and wind velocity. From this formula, the meteorologists in the Quartermaster Corps developed a table of wind-chill values, as well as graphic charts which depicted the relative comfort range for various combinations of wind speed and temperature.
     
    Wind-chill maps were also developed for North America and certain other areas, but they were in expectation of military operations in the Arctics and were not of specific practical value for winter tactics in temperate climates because they took no account of the element of wetness in combination with moderate temperatures. They are mentioned in this chapter only because they demonstrate that it is practical to measure wind chilling.
       
    Measurements of wind chill were not made either in the Mediterranean or European theater in World War II. Even if they had been made, they would have been of no practical value unless they had been based upon carefully controlled observations involving correlation between wind, temperature, and wetness.
       
    Although wind was undoubtedly a factor in the production of both trench-foot and frostbite on the Western Front in the winter of 1944-45, it is not
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30 Court, A.: Wind Chill. Bull. Am. Meteorol. Soc. 29:487-493, December 1948.


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feasible to study its effect by the comparative experiences of units of any size. Apparently, it was progressively more important as temperatures became progressively lower. This is another aspect of cold injury in which lack of data and of observations during actual combat indicates the need for further study and research for the benefit of both medical officers and commanders.
       
    Without these data, it is obviously impossible to discuss the effect of wind as an environmental factor except in general terms. Loss of body heat through wind chill, which is a heat exchange through convection, is only one of the ways in which the body loses heat. The degree of convective heat loss is always governed by the amount and type of clothing worn. Under no circumstances, according to Court, can convective heat loss account for more than 80 percent of the total body-heat dissipation.
       
    To reduce the facts to the simplest possible terms, the body generates heat, while clothing holds warm air in and keeps cold air out. Air in itself is an excellent insulator, and clothing is most effective in holding warm air in (1) when it fits loosely enough to allow for a layer of air next to the skin, (2) when the inner layers of the cloth of which it is composed are woven loosely enough to allow air pockets between the fibers, and (3) when the garments are worn in layers, so that there are air pockets and air layers between the layers of clothing. Still air is an insulator, and in it warmth is approximately equivalent to insulation. All movement, even winds of 5 miles per hour or less, reduces the effectiveness of the insulating properties of still warm air. The more porous the insulating clothing, the easier it is for the wind to penetrate and destroy the insulating properties of trapped and layered air. Wind accelerates the dissipation of body heat when the insulating properties of clothing are modified by sweating, evaporation, and the conduction of heat through it when it is wet.
     
    Wind chill, as Court pointed out, is only one of a number of problems which must be studied in physiologic laboratories before the loss of body heat by all means can be accurately computed. Among them are (1) the relation of breathing rates to the activity level, (2) the temperature and moist content of exhaled air, (3) the insensible perspiration rate at low temperatures, and (4) the surface temperature and radiative efficiency of the completely clad body. Court further pointed out that even when these problems are clarified, certain other considerations are likely to make measurements of wind chill and similar factors subordinate to subjective feelings of comfort or discomfort in the individual. These considerations include host differences in individuals, such as race, sex, age, body build, acclimatization, physical fitness, nutritional adequacy, sufficiency of clothing, and, in particular, mental attitudes.
       
    Terrain.- Terrain is an environmental factor which not only has a direct bearing on the incidence of trenchfoot but which also determines whether injuries caused by cold shall be predominantly trenchfoot, predominantly frostbite, or a combination of both. The weight of terrain as a modifying factor in cold injury has already been discussed in some detail in the section


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on multiple correlation studies of 21 divisions (p. 373). It is also discussed briefly in connection with altitude, precipitation, and thawing.
       
    Generally speaking, exposure in open, hilly, or mountainous terrain, usually covered by snow that does not melt in cold weather, is likely to produce frostbite. Trenchfoot is the more probable cold injury when temperatures are high enough to cause thawing, and when slush, mud, and water are underfoot. More often than not, combat activities are carried out in valleys, along streams, and in flat terrain subject to flooding and characterized by highwater tables. In flat terrain, the water table is often high, and it is also impossible to dig foxholes deep enough to avoid eventual flooding. In valleys and in low, flat terrain, troops in attack must cross muddy or flooded fields and swamps. During these crossings, they get wet, regardless of the clothing or type of footgear with which they are supplied.
       
    River crossings are among the most difficult military operations. They involve service support personnel, especially Engineer and Signal Corps personnel, as well as combat personnel, who usually bear the brunt of cold injury. Under these circumstances, it is virtually impossible to avoid wet feet and wet clothing over the lower extremities. If the temperature is within the trenchfoot range and if exposure is sufficiently long, the cold injury incidence will almost inevitably be high, and soldiers other than infantrymen will share the infantryman's liability to cold injury.
       
    Terrain may modify the incidence of cold injury in other ways. It may be of such a character as to offer shelter from the enemy and provide opportunities for adequate care of the feet. Conversely, it may provide concealment for the enemy and give him command of open country, with deadly crossfire and unlimited observation. Then, defending troops would be forced to remain in cramped positions in foxholes, with little opportunity for movement or for the employment of preventive measures against cold injury.
       
    The experiences of a number of units on the Western Front during World War II show the importance of terrain as a modifying factor in cold injury.
       
    Unit case history No. 6.- The 104th Infantry Division arrived in France early in September 1944. Its first combat experience was gained with the First Canadian Army, in active offense on the Maas River. The fighting was in agricultural country, which was low and flat and was traversed by many ditches and small canals. Foxholes promptly filled with water from a water table only 6 or 8 inches below the surface. After a week in these surroundings, the division was moved to a sector between Aachen and Eschweiler, where the terrain was rolling, fairly high, forested, and well drained. Combat action was sporadic offense, and there was some opportunity for shelter. The first peak of cold injury (chart 18, table 26) could be almost entirely explained as the result of operations of a new division, in terrain highly favorable to trenchfoot. The second peak, early in December, was the result of a different factor, namely, combat action, which took place in terrain not in itself conducive to trenchfoot.


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CHART 18.- Cold injury in 3 regiments of the 104th Infantry Division, European theater, for weeks ending 3 November 1944 through 5 January 1945
 
TABLE 26.- Cold injury in 3 regiments of the 104th Infantry Division, European theater, for weeks ending 3 November 1944 through 5 January 1945


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     The strikingly higher incidence of cold injury in one regiment, the 413th Infantry Regiment, is also easily explained. It operated in worse terrain than either the 414th or 415th Infantry Regiments, and at the same time encountered strong opposition, while the other two regiments were less strongly opposed.
  
    Unit case history No. 7.- The 26th Infantry Division, assigned to the Third U. S. Army, began combat operations in the November offensive in the area east of Nancy, where the terrain was low and marshy and rain fell daily. In a forced crossing of the Seille River, two companies of the 101st Infantry Regiment had to wade across in water more than waist deep. Within a day or two, cases of trenchfoot were being reported from all three companies. In the beginning, these companies had the highest trenchfoot rates of any units within the division.
       
    When the 338th Infantry Regiment from the same division was put into action, in a right flanking position, in open, flat, wet, muddy terrain, it was pinned down, within a short time, by enemy fire from Dieuze. It was 5 days before its relief was accomplished, and there was a large outbreak of trenchfoot as the result of the experience. The number of cases was greatly reduced as the division progressed to the upper Saar Valley, where combat action was chiefly in the towns; but a second, though much smaller, peak occurred in late November, when the troops had to fight through the open, muddy area of the Maginot Line (chart 19). Incidence of cold injury in the division is shown in the following tabulation:

[Tabulation]


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CHART 19.- Cold injury, 26th Infantry Division, European theater, 1 November through 15 December 1944
    Unit case history No. 8.- The 29th Infantry Division, which landed in France on D-day, had become a well-trained, well-led, experienced, and battle-wise division by the time it had fought across France and into Belgium. In the 2-week period 18 November through 1 December 1944, it was in an active offense toward the Roer River, in open, flat country, with poor drainage. The weather was only moderately cold, but there was much rain, and mud was deep. The 116th Infantry Regiment, which operated over open ground, often in water over the tops of the men's overshoes, had 72 cases of trenchfoot during this period (chart 20, table 27). The terrain over which the 175th and 115th Infantry Regiments fought was higher and drier and offered more protection. The numbers of cases in these regiments were 26 and 6, respectively.
       
    Unit case history No. 9.- The 78th Infantry Division did not arrive on the Continent until 22 November 1944. It was therefore without combat experience when, during the week ending on 15 December, it moved into the frontlines near Rotgen, Germany, and was immediately thrown into active offensive action. The terrain was hilly and partly forested, with many streams in the valley and much deep mud. Much of the time, the men were in exposed foxholes. When the 309th Infantry Regiment advanced, it was obliged to make several waist-deep stream crossings. When the 310th Infantry Regiment advanced, similar crossings were not necessary. The 311th Infantry Regiment was kept in reserve for most of the period. The 309th Infantry Regiment had 304 cases


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CHART 20.- Cold injury in 3 regiments of the 29th Infantry Division, European theater, for weeks ending 17 November through 29 December 1944
 
TABLE 27.- Cold injury in 3 regiments of the 29th Infantry Division, European theater, for weeks ending 17 November through 29 December 1944
 
of trenchfoot (chart 21, table 28), the 310th had 197, and the 311th had 18 during the period 9 December through 22 December.
       
    The experience of the 9th Infantry Division (unit case history No. 5, p.414) with respect to the influence of thawing has already been related. Its unit history also furnishes an excellent example of the modifying influence of terrain. Between 7 December and 17 December, a company of this division advanced to occupy trenches from which the Germans had been driven. The trenches were located in an open field and were filled with about 18 inches of water. Because of the intensity of enemy fire, the unit was pinned down in them for about 4 days. Twenty-nine of the one hundred and twenty men in the company con-


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CHART 21.- Cold injury in 3 regiments of the 78th Infantry Division, European theater, for weeks ending 1 December 1944 through 26 January 1945
 
TABLE 28.- Cold injury in 3 regiments of the 78th Infantry Division, European theater, for weeks ending 1 December 1944 through 26 January 1945.
 
tracted trenchfoot. A unit of similar size which eventually was able to get forward to relieve this unit brought with it straw and boards, to be used like the board tracks laid down in the trenches in World War I. As a result, the men kept themselves relatively dry and did not sustain a single case of trenchfoot.
       
    Altitude.- Altitude enters into the possible occurrence of cold injury for several reasons. It predisposes to the intensity of cold. Because of the cold, it further determines, to some extent, whether precipitation shall be in the form of snow or rain. In general, the type of terrain at higher altitudes is such


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TABLE 29.- Cold injury cases in armored, artillery, and infantry personnel of armored divisions, European theater, 28 October 1944 through 16 March 1945

as to discourage the formation of mud, marshy areas, large flooded areas, and broad streams. On the other hand, military operations in rough terrain are likely to be carried out in valleys, where the nature of the ground intensifies wetness. Exposure is usually greater when difficult operations are carried out in mountainous terrain. It is unlikely, however, that at altitudes at which ground forces usually fight, physiologic host changes caused by heights would be important enough to influence cold injury to any material degree.
       
    Temperatures likely to induce cold injury are reached earlier in the season in mountainous terrain, and daily fluctuations from low minimums at night to high maximums at midday appear to be greater in the mountains than on level ground. Combinations of frostbite and trenchfoot are prone to appear at the beginning and end of the cold injury season. Altitude thus introduces a number of environmental considerations, though in all of them the basic factor is the intensification of cold at progressively greater heights.
       
    American ground forces experienced combat in mountainous terrain both in Italy and in Western Europe during World War II, but data concerning the effect of altitude on the incidence of cold injury are not readily available.
 
Socioeconomic Environment  
   
    The social environment has a significant influence on the incidence of cold injury. As has been pointed out several times already, this form of trauma is an occupational disease of the infantryman, especially of the frontline rifleman. Infantrymen experience more trenchfoot than support or service troops in the same way, and for many of the same reasons, that outdoor laborers contract pneumonia more often than office workers.
       
    The susceptibility of infantrymen is well proved by examination of the incidence of cold injury in armored divisions. In four armored divisions which saw heavy service on the Western Front in the winter of 1944-45, 72 percent of 1,837 cases of trenchfoot were concentrated in the infantry battalions (table 29). Similarly, 87 percent of the 1,018 patients with trenchfoot interviewed in Zone of Interior hospitals (p.400) were infantrymen (table 30).
 


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TABLE 30.-Trenchfoot by arm or service in 1,018 patients hospitalized in Zone of Interior
 
    Combat action.- The most important single modifying factor in the causation of cold injury is the type of combat action. It is true that its influence cannot be entirely isolated from the concomitant influence of terrain, shelter, training, and experience. It is also true that combat action is, in turn, modified by leadership, the status of supplies of clothing and food, and the foot discipline of the individual soldier. Nonetheless, the intensity and type of combat determine the stress under which fighting men operate, with the result that fatigue, nutritional status, and psychosocial factors are also materially influenced by these considerations. These interrelated and interwoven considerations can best be summed up in the statement that combat action largely determines the degree of exposure and partly determines the susceptibility of the host and the opportunity which the individual soldier and his unit will have to carry out protective measures against cold injury.
     
    The incidence of cold injury varies according to the mission of the troops. Units in reserve or in rest areas have little. Units in the line on holding missions, or operating in static defense of various degrees, are subjected to greater exposure, and there is likely to be a moderate increase in the incidence of cold injury. Difficult defensive operations, which require irregular attacks to strengthen lines and maintain positions, are associated with almost the same high peaks of incidence that occur during trying offensive operations. Under some circumstances, in fact, this type of operation may be responsible for even larger numbers of cases.
       
    A study initiated by the Preventive Medicine Division, Office of the Chief Surgeon, ETOUSA, bore out these facts. When divisions were in reserve in rest areas, or were on the move, without combat duties, trenchfoot averaged 2.4 cases per day. When they were in static defense or engaged in holding operations, the daily average rose to 3.5 cases per day. When they were onactive defense, repelling enemy attacks, the average rose to 14 cases per day.
       
    Several of the unit case histories already related, particularly those recorded to demonstrate the influence of terrain, show equally well the part played by the type of combat action in the causation of cold injury. The specific situations summarized in the following histories also illustrate this point.


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CHART 22.- Cold injury in 3 regiments of the 2d Infantry Division, European theater, for weeks ending 3 November 1944 through 16 February 1945
  
    Unit case history No. 10.- The story of the 95th Infantry Division has already been told in part (p.402), to illustrate the effect of training and experience. By November 1944, it had experienced a great deal of combat and was a tried, reliable, and effective organization, with good discipline. Its total record of cold injury for the whole winter was among the best for any combat division, but a review of the records shows that even this staunch and battlewise unit had peaks of cold injury incidence when the going was hard (table 20, chart 10) .   

    This division operated in the Moselle Valley in the envelopment of the Metz fortresses. Crossings of the Moselle River were required, and the whole operation was difficult, especially during the 12-day period before the fall of Metz on 18 November. The peak of the cold injury incidence was reached on 19 November (chart 10), a date which, allowing a suitable timelag for the development of the injury, precisely fits the combat pattern. After Metz fell, the division moved eastward to Saarlautern in a rapid advance, but fighting was easier, and there was a reduction in the number of cases of trenchfoot. As the city was approached, however, fighting again became harder, and the Nied River had to be crossed. This was accomplished on 1 December. The difficult combat situation was again accompanied by a rise in the incidence of trenchfoot. 

  Unit case history No. 11.- The 2d Infantry Division landed in France on D-day plus 1, and by the middle of October had fought across France and Belgium to Saint-Vith. It remained in this area, in a static defense operation with active patrolling, until the first days of December. During November and the first week of December, the incidence of trenchfoot was negligible (chart 22, table 31). There was an immediate divisionwide increase in the number of cases, however, when the division went into an active attack against pillboxes near Elsenborn during the week ending on 15 December. The German


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counterattack on 16 December resulted in active defensive fighting for the following week, accompanied by a still greater increase in the trenchfoot incidence. During the week ending on 29 December, which was the second week after the German counteroffensive, combat action was again defensive, with active patrolling. The number of cases of trenchfoot fell precipitously, and there was no increase during the next several days, when combat took the form of static defense.
       
    The 23d Infantry of the 2d Infantry Division was attached to the 1st Infantry Division on the 15th of January 1945, and was in an active offense until the 22d, a period for which there was a marked increase in the incidence of cold injury for this unit. The remainder of the division was on defense and line holding. The 23d Infantry also had returned during the week ending 26 January. On the 29th of January 1945, the division jumped off in an offense toward the Roer River. During the first few days, the snow was deep and the weather cold, but with the onset of the February thaw the terrain became wet and very muddy. Troops were in foxholes in heavily wooded hills in which there were many villages. Almost immediately after the onset of this operation, there was a drastic rise in the incidence of cold injury which reached a peak of 179 cases for the week ending 9 February 1945. The division assumed
 
TABLE 31.-Cold injury in 3 regiments of the 2d Infantry Division, European theater, for weeks ending 3 November 1944 through 16 February 1945


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a static defense on the west bank of the Roer on 9 February, in which circumstances it remained until 28 February. During the first 2 or 3 clays of this action the principal component of cold injury in the division was frostbite. The thaw began about 1 February, and immediately trenchfoot and frostbite were almost equally apparent in the division (table 31). The last case of frostbite occurred on 8 February, but on 9 and 10 February there were 13 and 14 cases of trenchfoot, respectively (table 32).

TABLE 32.- Daily incidence of trenchfoot and frostbite, ,2d Infantry Division, European theater, 29 January through 11 February 1945
 
     Unit case history No. 12.-  The experience of the 5th Infantry Division in the fighting before Metz represents a different element of combat action. This division had been stationed in Ireland for 18 months, and foot discipline and the prevention of cold injury had been an important part of its training. The division landed in France shortly after D-day and, by early November 1944, had fought forward to the Metz area. In the November offensive, it jumped off toward Metz near Pont-a-Mousson, in the flat, rain-drenched Moselle Valley. Enemy resistance was heavy, and almost immediately cold injury began to occur in all three regiments (chart 23, table 33) though, for some inexplicable reason, it was at first disproportionately high in the 10th Infantry Regiment.
       
    Otherwise, the total experience by regiments throughout the difficult fighting preceding the reduction of Metz on 18 November demonstrates the effect on cold injury of movement versus a holding offense in severe combat. The division attack was on a broad, swinging front. The 11th Infantry Regiment maintained a holding and slow moving attack position on the left


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CHART 23.- Cold injury in 3 regiments of the 5th Infantry Division, European theater, 11-24 November 1944.
 
TABLE 33.- Cold injury in 3 regiments of the 5th Infantry Division, European theater, 11-24 November 1944
 


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flank, before Metz. The 2d and 10th Infantry Regiments moved rapidly in an enveloping maneuver in the center and on the right flank. Except for movement, all elements of the combat situation were essentially the same. Yet between 11 November and 21 November inclusive, the 11th Infantry Regiment had 302 casualties from cold injury, against 195 cases each in the 10th and 2d Infantry Regiments.
       
    Clothing supply.- Keeping warm and dry is fundamental in the prevention of overexposure to the elements. The kind and the adequacy of the clothing and footgear worn by combat soldiers therefore directly influence their susceptibility to cold trauma. The mere statement of that fact does not, however, cover the situation. There are a number of considerations implicit in it as follows:
       
    1. Clothing must be developed scientifically, to take advantage of air insulation and the layering principle. This means the provision of lightweight, wind-resistant, water-repellent outer garments, to be worn over layers of loosely woven inner garments. In World War II, the Quartermaster General approached this problem on the basis of so-called clothing assemblies. Research on clothing in relation to man's physiologic needs in extremes of climate and the development of fabrics with known protective qualities led to the establishment of types and designs for various articles of clothing which, when worn together, gave maximum protection against cold. The total uniform for this purpose was designated a clothing assembly. A great deal of effort and research went into the development of these assemblies to meet specific conditions, and, on the whole, both principles and designs were good.
       
    2. Clothing must be designed from the standpoint of practical possibilities. It is probably not possible to design combat clothing that will adequately protect fighting personnel under extreme conditions of intense combat activity in cold and wet weather. In these circumstances, long exposure under great stress can scarcely be avoided. The most practical plan, therefore, in designing clothing for military operations in the winter, is to take into account only average conditions of exposure to weather in the coldest months of the year and to attempt to protect the combat soldier within a range of  10° F. above and below these averages.

    3. Clothing and footgear must be designed so that there will be no interference with circulation in any part of the body.
       
    4. Clothing must be worn so as to take advantage of the principle of insulation; that is, air must be present between the skin and first layer, as well as between all succeeding layers.
       
    5. Clothing must be in proper supply. Adequate supplies must be brought to the division area. They must also be distributed to the smallest units farthest forward in such a way that individual soldiers will be able to change into warm, dry clothing as the need arises. The supply of all necessary items to tens of thousands of men scattered in combat units along several hundred miles of a long fighting front is a major problem in logistics.


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    6. Even granting that clothing is properly designed and that supplies and distribution of clothing assemblies are sufficient, it is still necessary, for the greatest protection to be obtained from clothing, that both the commander and the individual soldier understand the principles involved and the methods of utilizing the garments provided. The importance of this consideration was not always realized in World War II, but failure to assemble the uniform for wear as intended can greatly decrease its ability to protect the wearer against cold. Since trenchfoot is caused not only by exposure of the feet but also by loss of body heat, insufficient protection of the torso by failure to include the sweater or the jacket or some other garment in the assembly can be responsible for the development of cold injury.
       
    The chief responsibility for the development and production of all types of clothing rests with the Quartermaster General of the Army. Before the entrance of the United States into World War II, the Office of the Surgeon General had had little to do with the development of winter clothing, and the Attu operation was over before there was active medical participation in this phase of operations.
       
    In June 1942, the National Research Council set up a subcommittee on clothing, whose personnel included, among others, representatives from the Office of the Surgeon General of the Army and of the Navy, the Office of the Air Surgeon, the Medical Research Laboratory at Fort Knox, the Rochester Desert Laboratory, the Harvard Fatigue Laboratory, and the Textile Foundation; liaison personnel from the Royal Air Force also were included. The original function of this committee was to develop a lightweight, functional flying uniform for aviators, but this function was soon expanded to cover clothing problems of naval and ground forces. The observations made have been brought together by Newburgh, 31 who served as chairman of the subcommittee. The text includes data on acclimatization, methods for determining heat exchange, physiologic adjustments to heat and cold, and studies of the protective properties of clothing. This resume of what is known of host reactions and responses to heat and cold simply emphasizes the need for continued research if man's ability to cope with cold trauma in war is to be fully understood.
       
    The work of this subcommittee was complemented by the work carried out at the Armored Medical Research Laboratory, which had been established at Fort Knox in September 1942, with the specific mission of conducting research on physiologic problems of practical significance to this branch of the service. Special attention was directed to the study of the soldier in relation to his duties. Later studies included tests of the adequacy and range of winter combat clothing.
       
    The problems of the choice, supply, and utilization of clothing in the Aleutians and in the Mediterranean and European theaters have been presented in detail under the appropriate headings (pp. 90 and 111) . Of interest in this connection is the report by Maj. Paul Siple, the representative of the Quarter-
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31 Newburgh, Louis H.: Physiology of Heat Regulation and the Science of Clothing. Philadelphia: W. B. Saunders Co., 1949.


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master General, who arrived in the European theater in February 1945, with the mission of observing the adequacy of the supply and distribution of winter clothing. In essence, he reported as follows:
       
    While the complete clothing assembly designed for frontline troops was in itself adequate, it was provided in insufficient quantities. In many instances, too, it was provided so late in the winter that it was not available during the coldest weather, when it was most needed. The campaign was therefore fought by most combat personnel in uniforms deficient in proper protection because of inadequate insulation, poor balance of insulation, lack of windproofness, lack of water repellency, and faulty closure.
     
    The clothing initially provided for winter combat in the European theater, the report continued, did not provide ample enough insulation because it was poorly balanced, it lacked sufficient thickness, it was worn inefficiently, and it did not provide a satisfactory means of preventing movement of air from destroying insulation through the garments or at the points of closure. As an example, the legs were covered by only two layers of clothing, wool drawers, and wool serge trousers. When the soldier was standing, even when he was not exposed to wind, this covering provided only about half an inch of insulation and only about two-thirds of the protection needed under average conditions. When the absence of windproofness in the wool trousers was taken into consideration, the warmth-retaining value of protection for the legs was lowered by about 50 percent. When the man was seated, with underwear and trousers tight over the seat, thighs, and knees, the protection was even less. It was easy to understand why soldiers frequently complained of cold hands and cold feet. Loss of body heat, as a result of the defects in clothing just described, and additional losses through openings of the garments at the neck, the wrists, and the ankles reduced the body temperature to the point at which the most exposed parts of the body, that is, the hands and feet, gave the first evidence of the imminence of possible cold injury.
       
    There were other reasons why the clothing situation was often unsatisfactory. One was that, because of lack of training in the use of clothing in cold weather, items of the uniform assembly were often misassembled. In other instances, the items could not be assembled properly because of piecemeal issue.

  Special types of winter clothing were in short supply in the Army in Europe throughout most of the winter season; but standard items, such as underwear, wool shirts and trousers, overcoats, field jackets, and gloves, were always in adequate supply in the theater. Even standard items, however, were not always available to the troops. Because of the urgent tactical necessity for mobility of the individual soldier in combat, commanders sometimes allowed their men to discard clothing which was not needed during strenuous activity. Afterward, resupply or redistribution was not always possible. 
       
    Footgear.- The United States combat boot, as pointed out earlier (p.150), was not well designed. It tended to shrink after it had become wet, and the uppers were so scantily cut that, however tightly they were laced, they could not be brought together. In addition, and also as previously noted, the United


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States soldier had been accustomed to tight-fitting clothes and snug-fitting shoes in civilian life, and he carried those habits with him into the Army. For these and other reasons, there were numerous errors in the fitting of army shoes. In many instances, no allowance was made for the fact that feet tend to enlarge under marching and other strenuous activities. Nor was sufficient, if any, allowance made for the fact that heavy woolen socks, or two pairs of socks, would be worn during the winter instead of the thin cotton socks worn during the summer. The soldiers, it must be granted, sometimes created their own difficulties. When they had been properly fitted originally, they would trade shoes among themselves until they found the snug-fitting kind to which they had been accustomed in civilian life.

    Similarly, when galoshes were provided, they were not always worn. Sometimes the men were directed to leave them behind. Sometimes they simply discarded them of their own initiative because they were cumbersome to wear into combat.
       
    Socks in the lighter weights were in generous supply at all times in the various theaters of operations. Heavy wool ski socks were scarce throughout the winter combat period in the first winter in Italy, as well during the period of heavy fighting and cold, wet weather on the Western Front.
       
    It is easy to speculate on the effects of these and other deficiencies in clothing and footgear, and on bad practices in their use, but it is less easy to prove exactly how they influenced the incidence of cold injury. The effect of clothing and footgear per se cannot be isolated from other factors and measured alone. The combat situation and the idiosyncrasies of supply must always be taken into account. So must human factors. Footgear, for instance, cannot be designed that will force the soldier to wear it into combat, or to change his socks at stated intervals, or to remove his shoes at night, when he knows full well that lie may have to leave the scant protection of his foxhole at a moment's notice.
       
    Even when allowance is made for these considerations, the incidence of cold injury in both the Mediterranean theater and the European theater seems clearly related to the completeness of provision of clothing and footgear. A study by the Preventive Medicine Division, Office of the Chief Surgeon, ETOUSA, showed unmistakably that the total cold injury rate during the period of combat was 4.3 per 1,000 for divisions fully equipped in November 1944, 10.5 per 1,000 for those not fully equipped until December, and 11.7 per 1,000 for those not fully equipped until January 1945. The study also revealed that, when only trenchfoot was related to the degree of completeness of equipment, the rates were, respectively, 2.5 for November, 6.0 for December, and 8.5 for January. These proportions might have been expected, since footgear is not the only item of clothing related to the production and prevention of cold injury.
       
    The whole experience in Italy and western Europe in World War II serves to emphasize the need for simpler and more efficient types of clothing and footgear to reduce exposure during winter operations. The Theater Quarter-


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master was emphatic on this point. In March 1945, at the Paris conference (p.184), he pointed out that the uniform must be made simple and basic, if only because transportation is limited in wartime and allowances for the movement of supplies would therefore always be limited; food, gasoline, and ammunition have priority in tonnage moving forward. Similarly, the production of clothing in the Zone of Interior would be expedited if all items were kept simple and uniform; there were limits to what could be produced when an army was growing rapidly and straining production of a wide variety of items. The quality of the raw materials and the workmanship in British uniforms, the Theater Quartermaster concluded, might not meet United States standards, but British clothing was simple, and it had been kept uniform, with the result that supplies were adequate all during the fighting in Europe.
         
    The experience in Italy and in western Europe also showed that supply procedures and practices must be simplified and that command and all other personnel must be thoroughly trained in the most efficient use of the clothing and footgear provided.
   
  As the war progressed, special items of clothing were reduced to a minimum. Observers from the Quartermaster Corps not only studied the use of the various items under as many conditions as possible but also went to great lengths to sample soldier opinion about them. The results of these surveys sometimes appeared to have more influence on changes of policy and clothing directives than they merited, a fact which emphasizes the need for better training of the soldier in the efficient use of clothing and what could be expected from it.
       
    Shelter.- Shelter is an important consideration in the incidence of cold injury because it is a means to shorten periods of exposure to the elements, as well as periods of exposure to enemy observation and fire. Seeking shelter to avoid exposure to cold and wet in combat is as natural and as sensible as coming into one's own home to avoid the rigors of a winter day. It is not an easy matter, however, to provide shelter for troops in combat. Though terrain enters into the problem, whether or not shelter is practical depends chiefly upon the tactical situation.
       
    Under many combat situations, it is impossible to provide shelter of any kind except that offered by natural features of the terrain and the hasty digging of individual foxholes. What can be provided ranges from none at all, which means complete exposure in open ground, through quickly improvised, unimproved foxholes, foxholes in which there is time for improvement and greater protection, tents, dugouts, pillboxes, other improvised shelter and damaged buildings, to, finally, unscarred buildings suitable for the comfortable housing of troops. Soldiers able to take shelter in buildings, basements, or dugouts, or even tents and improved foxholes, are obviously much better able to look after themselves and to take the measures necessary to pre vent cold injury than are those who must pass their nights in hurriedly dug foxholes.
       
    As the war progressed on the Western Front in the winter of 1944-45, the men developed many expedients to improve their lot, even in the crudest of shelters. Often they obtained and utilized some form of heat, even in far


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CHART 24.- Cold injury in 3 regiments of the 90th Infantry Division, European theater, 14 November through 21 December 1944

forward positions, such as charcoal braziers or hexyl methylamine tablets, which provide fairly intense heat. At other times, when observation by the enemy did not forbid it, exposed soldiers poured gasoline on the ground or into containers filled with loose earth or sand or constructed some other similar device and then set fire to the fuel to provide the warmth they needed for protection from the cold. Many hundreds of gallons of priceless motor fuel were thus consumed. This wastage pointedly indicates the need for developing practical means and methods for providing shelter and heat under adverse conditions, as well as the need for the provision of more satisfactory types of clothing and footgear. Incidentally, the use of heat in this manner may sometimes have added to the seriousness of the cold injuries sustained instead of decreasing their incidence (p.317).

    Some of the unit histories already related illustrate the influence of the element of shelter as well as of terrain and combat. Other illustrations follow:
   
    Unit case history No. 13.- The 90th Infantry Division was engaged in operations in the Saar Basin during the first half of December 1944. Two regiments crossed the Saar River at Dillingen on 6 December. As the fighting developed, the 357th Infantry Regiment was pinned down in foxholes in the open, while the 358th and 359th Infantry Regiments, although operating against equally resolute resistance, fought in the town of Dillingen where some shelter was available as well as some protection from exposure. By 12 December (chart 24, table 34), the 357th Infantry Regiment had experienced a sharp  


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TABLE 34.- Cold injury in 3 regiments of the 90th Infantry Division, European theater, 13 November through 21 December 1944


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CHART 25.- Cold injury in 3 regiments of the 102d Infantry Division, European theater, 24 November 1944 through 2 February 1945

rise in trenchfoot cases; between that date and 14 December, inclusive, it reported 160 cases, while little increase in incidence was noted in the 358th and 359th Infantry Regiments. The principal difference in conditions was that the latter regiments had some shelter.
       
    Unit case history No. 14.- A still better illustration of the importance of shelter is furnished by the experience of the 102d Infantry Division. This division did not arrive in France until late in September 1944 and therefore was new to combat. On 1 November, the 406th Infantry Regiment was detached and the other troops were placed in an inactive defense position where they remained until 27 November. On 28 November, the 406th Infantry Regiment was returned to divisional control. From that date until 3 December. an offensive action toward the Roer River was conducted in the Mach area. For the weeks ending on 1 December and on 8 December, there was a sharp increase in cold injury (chart 25, table 35).

    Between 4 December 1944 and 2 February 1945, the division remained in the same sector, in a quiet defensive position. The men of the 405th and 407th Infantry Regiments were for the most part in buildings and basements and therefore had relatively adequate shelter. The 406th Infantry Regiment, on the other hand, because of the sector it had to defend, had to seek shelter in foxholes. The strikingly higher incidence of trenchfoot in this regiment after the initial offense and during the static defensive weeks, can be accounted for by one principal differential, the absence of adequate shelter.


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TABLE 35.- Cold injury in 3 regiments of the 102d Infantry Division, European theater, for weeks ending 24 November 1944 through 2 February 1945
       
    Command leadership and attitude.- Leadership is an intangible quality which is difficult to define or measure precisely. It is not the intention to attempt to do either here, but some general statements may nonetheless be made concerning it.

    Leadership is a socioenvironmental factor. The standard of leadership materially influences the unit liability to cold injury. Lack of leadership predisposes to a high incidence. When leadership is good, the discipline and esprit de corps are such that the tedious and sometimes tactically disadvantageous measures which are required to prevent cold injury are willingly carried out for the good of the command. Good leadership can modify or control many of the host and environmental factors responsible for cold injury. Good planning, astute decisions, and firm example can determine the outcome of combat action. Good leadership is always concerned with the welfare of the individual soldier. The necessary steps are therefore taken to insure appropriate supplies of food and clothing, adequate medical facilities, and rest and rotation schedules that will reduce fatigue and increase fighting efficiency.
       
    A good commander understands and accepts his responsibility for the prevention and control of mass diseases and injuries that may affect his unit. In so doing, he makes full use of the special knowledge and skills of his technical advisors. He cannot, because of tactical and other circumstances, always accept the advice given him, at least in all details, but he is very certain of the consequences when he rejects the advice. He does not wait until a large number of casualties from cold injury has lowered the effectiveness of his


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unit. Instead, he institutes education, training, and indoctrination programs well in advance of the possible occurrence of cold injury. It is by no means the least important manifestation of good leadership that a good commander establishes such liaison and understanding with the men under him that they appreciate the role of the unit in the general conflict. They know what they are fighting for, and they understand the reasons for the policies and procedures they are called upon to carry out. United States soldiers will always respond willingly when they understand the rationale of such measures and the benefits to be derived from them for themselves and their units. It is almost impossible to force them to carry out measures whose rationale they do not understand.
       
    This is not theoretical reasoning. It was repeatedly observed in both the Mediterranean and the European theaters that well-led units always had the best average records for cold injury. Numerous divisional records prove this point. The story of the 29th Infantry Division has already been related (unit case history No. 8, p. 421). This battle-tried unit, in spite of hard fighting, had only 164 cases of cold injury during the entire winter of 1944-45 on the Western Front. Similarly, the record of the 95th Infantry Division (unit case history No. 3, p. 402), which had even harder combat missions than the 29th Infantry Division during this winter, illustrates the effects of excellent leadership. During the hard fighting between 1 November 1944 and 15 January 1945, it had only 325 cases of cold injury of all types.
       
    The following record of the 87th Infantry Division represents both good and bad leadership:
       
    Unit case history No. 15.- This unit was assigned to the Third U. S. Army early in December 1944. It had had no previous combat experience. On 11 December, it was committed in a drive toward Saareguemines, directly east of Metz. The weather was moderately cold, and there was daily rainfall. The terrain consisted largely of ridges and valleys and was not forested, so that the ground was very muddy.
       
    The story is now best continued by regiments:
   
    The 346th Infantry Regiment was the first to gain contact with the enemy. Its casualties were heavy at first and the attack bogged down on a gently sloping hillside because of the intensity of enemy fire. On its second day of combat, casualties were again high, and 12 cases of trenchfoot made their appearance. At the same time, combat exhaustion cases accounted for 15 percent of total casualties. Battle casualties dropped to 7 on the fourth day. On the following day, which was the 15th of December, the number of trench-foot cases far exceeded battle casualties and for the most part came from the 1st Battalion. On the 6th day of combat, this battalion alone had 206 trench-foot casualties. By the end of a week of fighting, the 346th Infantry Regiment had experienced over 400 cases of trenchfoot in men fully equipped with overshoes and winter clothing (chart 26, table 36; chart 27, table 37).


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CHART 26.- Cold injury in 3 regiments of the 87th Infantry Division, European theater 11-22 December 1944

    The record of the other regiments was quite different. The 345th Infantry Regiment was not committed until 30 December and was in intensive combat only for a matter of days. It experienced only a few cases of frostbite. The 347th Infantry Regiment was committed to the support of the 346th the fourth day of the battle (14 December). It began to suffer casualties from trenchfoot almost immediately, but at no time in the period under consideration did the daily number of cases exceed 42, and the total for the whole period was only 178.
       
    The records of the 346th Infantry Regiment show that the regimental commander and the commanding officer of the 1st Battalion were chiefly at fault in the poor record of this regiment, and especially of this battalion, with respect to cold injury. Lack of progress in the attack, with demoralizing enemy fire, resulted in a considerable break in morale. A complete breakdown in foot discipline was the direct result. Poor attention to the welfare of the riflemen in the regiment also played a part in the high incidence of trenchfoot.


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TABLE 36.- Cold injury in 3 regiments of the 87th Infantry Division, European theater, 11-22 December 1944
 
CHART 27.- Cold injury in 3 battalions of the 346th Infantry, 87th Infantry Division, European theater, 11-22 December 1944


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TABLE 37.- Cold injury in 3 battalions of the 346th Infantry, 28th Infantry Division, European theater, 11-22 December 1944  

    Because training was not good enough to support the troops in time of trial, the regiment suffered a serious point epidemic of cold injury. It is true that this was a new, untried, and inexperienced unit. It was called upon to spearhead an attack in difficult terrain and in opposition to heavy German forces, which used tanks in defense, but it is equally true that leadership was the principal factor responsible for the high incidence of trenchfoot.
       
    The story of these regiments emphasizes a vital principle in the prevention of cold injury; namely, that this type of injury, with its prevention, is a problem of the small units. One regiment of this division (chart 26) was careless. One battalion in this regiment (chart 27) was at fault. It is interesting to speculate whether or not the errors could be traced down to poor leadership in certain companies. It is probable that the same principles held in them.
       
    Training and experience.- From the standpoint of cold injury, training and experience are inseparable from individual and unit discipline. Effective training is based on good discipline, and the development of good discipline is a part of the soldier's training. When men are well trained and properly disciplined, they profit from experience and become better able to look after themselves and save themselves from trauma, whether it be from enemy weapons or from cold.
       
    The good record of some experienced and battlewise divisions with respect to the incidence of cold injury has already been mentioned. Among them are the 104th Infantry Division (chart 18) and the 90th (chart 24). The 99th Infantry Division furnishes a reverse example of the effect of inexperience and lack of battle training.


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CHART 28.- Cold injury, 99th Infantry Division, European theater, for weeks ending 10 November 1944 through 16 March 1945
 
   Unit case history No. 16.- The 99th Infantry Division arrived in England in October 1944, landed in France during the first week of November. It was committed to combat on 9 November, in a static defense, with active patrols. The country was hilly and partly forested. The weather was moderately cold. It rained, and some snow fell. The ground was either muddy or slushy. The division remained in the line under these conditions through 12 December. Cases of cold injury, principally trenchfoot, began to appear almost as soon as it was committed, and there was a peak of 194 cases for the week ending 24 November (chart 28, table 38) . Weather conditions were favorable for its occurrence, it is true, but combat missions were light, and the high incidence could be attributed only to inexperience and to lack of training in the measures required to prevent cold injury. A contributory factor may have been the incomplete provision of galoshes during this period.
       
    A second, even larger, outbreak of cold injury occurred between 13 December 1944 and 5 January 1945. On 13 and 14 December, the 395th Infantry Regiment and a battalion of the 393d Infantry Regiment were in active combat. The action shifted to heavy defense against the German midwinter counterattack of 16-18 December. Between 19 December and 28 December, a retrograde movement was made, and combat action took the form of active defense. Between 29 December and 28 January, action was also defensive, with active patrolling. The second outbreak of cold injury was, like the first, largely attributable to the inexperience of the troops, though intensification of the combat action also played a part.


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TABLE 38.- Cold injury in 3 regiments of the 99th Infantry Division, European theater, for weeks ending 10 November 1954 through 16 March 1945  

    A third peak of cold injury in this division occurred between 26 January and 16 March 1945. From 2 February onward, operations were in melting snow, rain and mud, at temperatures between 30° and 40° F. (-1.1° and 4.4° C.), but the high incidence was also to be explained by heavy combat, sometimes in extreme cold.   

  Foot discipline.- Foot discipline in itself cannot, of course, be separated from discipline in general. It is part of both unit and individual training. The incidence of cold injury was always low when it was good. Foot discipline, moreover, was best in those divisions in which the practice of inspection of the feet was established early, and in which the inspection was not only by commissioned officers but also by noncommissioned officers down to, and including, the squad level. Even under severe combat conditions, it was repeatedly observed that when discipline was good sufficient time and safe enough surroundings could usually be found for the use of protective measures. Even if daily care was not possible, in most situations care of the feet could be resumed before the end of the mean incubation period for trenchfoot, that is, approximately 3 days, though as temperatures approached the freezing point the margin of safety became less.


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CHART 29.- Cold injury in 3 regiments of the 45th Infantry Division, European theater, for weeks ending 3 November through 29 December 1944

    A study by Colonel Gordon's office showed that, during the winter of 1944-45, six divisions which had not been in combat before 1 November 1944 averaged 15.5 cases of cold injury per (lay of combat, while 13 units with long combat experience averaged only 7.6 cases per day. Although several factors undoubtedly helped to explain this difference, the observers attributed it chiefly to better foot discipline in the experienced divisions. The inexperienced divisions had not received adequate training in the individual care of the feet, or, if they had been trained, they had not come to recognize the importance of the training and therefore did not apply what they had learned. As a result, when they were first committed to action under conditions favorable to trenchfoot, many became casualties to cold and mud.
       
    Intense combat activity influenced the incidence of cold injury, at least indirectly, because it brought about a relaxation of foot discipline. It was the observation of a number of division surgeons that when the incidence of cold injury was rising a prompt decline would ensue, regardless of combat activity, whenever commanding officers took a firm stand in insisting upon individual care of the feet.
       
    A specific example of the effect of foot discipline is furnished by the three regiments of the 45th Infantry Division as follows:
  
  Unit case history No. 17. - All three regiments of the 45th Infantry Division fought under similar conditions, with roughly similar missions, between 28 October and 29 December 1944. During this period (chart 29, table 39) the 180th Infantry Regiment had 48 cases of cold injury, the 179th, 108 cases, and the 157th, 209 cases. When the division was surveyed, the only explanation found for these differences was that training was rather poor in the 157th Infantry Regiment, was satisfactory but no more in the 179th, and was excellent in the 180th.  


446
 
TABLE 39.-Cold injury in 3 regiments of the 45th Infantry Division, European theater, for weeks ending 3 November through 29 December 1944 

    The story of the 9th Infantry Division has already been used (unit case history No. 5, chart 17) to illustrate the effects of both thawing (p. 414) and terrain (p.422). It also illustrates the effect of foot discipline. Both frostbite and trenchfoot were kept at low levels. There was one small outbreak of trenchfoot in the middle of November, before the troops were completely supplied with galoshes, and a second, minor elevation in December, coinciding with a period of active defense. When this division was surveyed, it was concluded that its excellent record could be attributed to a number of factors, including (1) its battle experience, (2) the early date at which it was supplied with galoshes, (3) the extensive use of drying tents, (4) the unusual ingenuity shown in obtaining and issuing charcoal braziers for the use of frontline troops, and (5) the intensive program of instruction, in which the burden of prevention of cold injury was placed on the individual soldier.
       
    Similar observations could be multiplied. All of them can be interpreted as indicating the importance of foot discipline, which includes familiarity with the measures which the individual soldier can use to prevent cold injury and the diligent application of these measures.
       
    Rotation.- Rotation, or the regular relief of troops from frontline positions in which exposure to the elements is great, materially influences the incidence of cold injury. The most adverse conditions of weather and terrain can be tolerated by combat soldiers for short periods if they can be rotated within units or by units, both large and small, and thus be provided with opportunities to carry out appropriate control measures.


447
 
    The practice is beneficial at any level, from individual frontline riflemen and squads through progressively larger units by echelon, up to and including whole divisions. A good rotation policy begins with the individual soldier in the frontline. In forward areas, it need consist of no more than the opportunity to withdraw from his foxhole to a crude shelter a few hundred yards to the rear, where, in relative safety, he may change his clothing, exercise a little, and carry out appropriate measures, including massage, for the care of his feet. In the battalion area, better arrangements can be made for foot care, and facilities improve progressively in regimental and division areas. Somewhere along the line, bathing and laundry facilities are available, the men can obtain a few hours of rest, and, under ideal circumstances, they are provided with hot food and the morale-lifting advantages of the Red Cross truck and of getting mail and writing letters home.
       
    Intervals of rotation should vary according to the size of the units. In frontline units, the rotation of individuals and small units depends upon weather and the intensity of combat action. In World War II, it was the consensus of division surgeons that a period of 3 days or more was usually required for trenchfoot to develop at temperatures above freezing, while, below that level, frostbite could develop in a few hours. In progressively larger units, rotation should be progressively less frequent but for longer intervals. In addition to the importance of rotation in the prevention of cold injury, its employment for this cause bolsters morale in general, lessens fatigue, and decreases losses from neuropsychiatric causes.
       
    A definitive rotation policy was never established by United States armies in Europe. Instead, divisions determined and executed their own rotation practices, while, within divisions, the policies were usually left to the discretion of regimental or battalion commanders. Under these circumstances, policies and practices naturally varied widely. They were good in some units and poor in others. In all, they were of necessity greatly influenced by the exigencies of combat.
       
    During the German counteroffensive in December 1944, the defense operation in the first few days was so urgent that good rotation practices could not be executed. The intensity of the fighting during the later United States counterattack had the same inhibiting effect. The combat situation was therefore partly responsible for the second Army-wide cold injury epidemic on the Western Front (chart 15) . In situations such as these, the determination of the extent of rotation must be a command decision, but the establishment of the general principles of rotation by army, or even by army group, and the insistence that these principles be applied consistently within the limits permitted by the combat situation, would have influenced the cold injury incidence downward in World War II. It would also have reduced losses from combat exhaustion and psychoneurosis.


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    The effectiveness of rotation in reducing the incidence of trenchfoot is well illustrated in the following experience of the three regiments of the 35th Infantry Division:
       
    Unit case history No. 18.- This division landed on the Continent in July 1944 and fought across France in the Third U. S. Army. At the beginning of the November offensive, it was in the line east of Nancy, in muddy, rolling, open country near the Sellle River. As the offensive opened, a division order was issued directing that galoshes be left behind.
       
    The 320th Infantry Regiment made an all-night march to get into position, then crossed the river. Three days later, it began to report trenchfoot casualties (chart 30, table 40). At this time, the 134th and 137th Infantry Regiments went into action. Rain fell continuously, and the foxholes were usually half filled with water. During the first 9 days of the operation, the 134th and 320th Infantry Regiments bad, respectively, 161 and 163 cases of cold injury. For the same period, the 137th Infantry Regiment had only 36 cases. Conditions for all three regiments were substantially the same, with one exception: The 137th Infantry Regiment fought through a. few small, built-up areas and had what amounted to daily rotation of small groups, to allow for drying the clothing and caring for the feet. It was the opinion of those who studied the cold injury situation in the three regiments that it was principally good rotation practice in one regiment, as opposed to the lack of rotation in the other two, that accounted for this striking difference in the trenchfoot experience.
 
CHART 30.- Cold injury in 3 regiments of the 35th Infantry Division, European theater, 8-30 November 1944


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TABLE 40.- Cold injury in 3 regiments of the 35th Infantry Division, European theater, 8-30 November 1944  

Interrelationships of Causative Factors  

    The following records of the 3d and the 36th Infantry Divisions summarize effectively much of what has been discussed in the earlier pages of this chapter.
       
    Unit case history No. 19.- The 3d Infantry Division, a battle-experienced, hard-hitting unit, which was the mainstay of the Seventh U. S. Army, reduced the Colmar Pocket, and then fought out, into the Colmar Plain toward the Rhine during January and February 1945. The interrelationships of many of the modifying factors of cold trauma which have been discussed are apparent in the graphic record (chart 31). When the incubation period of cold injury is considered, the influence of weather, type of combat action, wetness from river crossings, terrain, and adequacy of clothing and equipment is well demonstrated.


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CHART 31.- Cold injury incidence, 3d Infantry Division, European theater, 20 January through13 February 1945


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Unit case history No. 20.- The 36th Infantry Division had a considerable experience with cold injury in Italy during the winter of 1943-44. In the fall of 1944, it participated in the landings in southern France. During the succeeding winter, it found itself in almost constant contact with the enemy. In its progress, it fought on a wide front, through difficult, mountainous terrain. All movement of any consequence had to be on foot. After 15 September, the weather was cold, and, during November, rain fell almost continuously. Several streams had to be crossed, and the constant rains kept the troops wet even when they were on high ground.
       
    The cold injury experience to date and the problems encountered during 1944 were summarized by the surgeon of the 36th Infantry Division in his December 1944 sanitary report, as follows:
        
    Trench foot has caused a serious loss of manpower within the Division during combat operations in the winter months in Italy and France due to the cold wet climates encountered. The highest incidences were reported during the months of January with 401 cases, February with 270 cases, November with 279 new and 97 recurrent cases, and December, with 155 new and 45 recurrent cases. During the month of November, 77 cases of trench foot were received over a four day period from one Regiment of the Division that was attacking during a driving rain. These troops had been issued an extra pair of heavy wool socks and an extra light wool pair. Although most of them had shoepacs they had four times as much trench foot as the rest of the division. The other two Regiments of the Division were in a holding position and had a total of 19 cases of trench foot. Another observation of two adjoining companies under the same conditions of exposure was made when one company had 10 cases of trench foot over a six day period while the other company had 3 cases. It was found that the men of the company having 10 cases had had no exchange of light wool socks while those of the other company had dry socks exchanged 5 times. This was corrected. The marked decrease during the month of December is attributed to comparatively dry weather encountered during the month and to the educational program conducted during the months of October and November on foot hygiene and the prevention of trench foot. Shoepacs were issued to the troops during the month of November with instructions for their proper wear and the importance of changing to dry clean socks and dry inner soles daily. Approximately 1,700 men of this division do not have shoepacs or overshoes because of the lack of proper sizes in Quartermaster stocks. Every effort is being made to issue combat boots of sufficient size to permit wearing of heavy wool socks and a light wool pair. A system has been worked out by which the infantry S-4s [supply] replace the dirty socks with clean dry socks daily by sending the clean socks forward with the daily ration issue. The high casualty rate among Commissioned and Non-Commissioned Officers, resulting in frequent turnover of the command while in combat causes the necessary supervision of foot hygiene in small units and footgear discipline to be less efficient than is desired, even though constant attention is given to this matter in Battalion, Regimental and Division Headquarters. Instructions on prevention of trench foot given at the direction of Seventh Army to personnel of Replacement Depots and Convalescent Hospitals is believed to be an important aid in the educational program against this disease. Random comments in the report of the trench foot survey of the 36th Division emphasize still other causes for the high trench foot incidence:
       
    "Unfortunately, the tactical situation has largely precluded the possibility of rotation of men. No regiment has been in reserve and riflemen have been in the line for long periods of time.
       
    "There has been no policy to set up houses or tents to be used specifically as drying rooms for front line soldiers. It is felt that if houses or dug-outs are available, soldiers, will go to them to warm themselves and build fires to dry their clothing of their own accord.


452  

    "Shoe pats were issued during the second week of November. About 2,000 men do not have them because of wrong sizes. * * *
      
     "This division tried to get socks to front line soldiers each day with rations. It is believed that sock exchange is fairly satisfactory.
       
    "The division went through the Italian winter campaign and officers and men in that campaign are well trained in the prevention of trench foot. Replacements are not well trained in care of the feet.
      
     "* * * trench foot is a disease of riflemen. With the exception of a small percentage of supporting troops, such as company aid men and combat engineers, the disease should not occur in any except infantry riflemen. Even the heavy weapons companies have very little trench foot.
       
    "Battle conditions play a very important part in the development of trench foot. The surgeon believes that 24 to 36 hours exposure in wet, cold weather, without supply, w be sufficient to produce trench foot.
       
    "The Surgeon believes that control of trench foot is purely a command function. If the command is well trained in the prevention of trench foot and realizes its importance, the rate of trench foot will be very low in that organization. He also points out that when unit officers are frequently changed, the trench foot incidence is always higher than in units which retain their officers for longer periods."
      
    It was not until late in January 1945 that a thoroughgoing, well-rounded cold injury prevention program was, or could be, instituted in the 36th Infantry Division. By this time, all replacements were receiving detailed instruction on the proper care of the feet, both when they first were assigned to the division and upon assignment to regiments. Supplies of shoepacs, light wool socks, and ski socks were now adequate. In its holding operations, the division had found it feasible to establish a good rotation system by the use of houses, dugouts, or tents immediately behind the frontline, where each man could spend an hour out of every 6 or 8 hours warming himself, changing his socks, and massaging his feet.
       
    Even under these improved conditions, a report by a unit surgeon of this division for January 1945 noted that "the lack of close supervision of some small unit commanders has caused the incidence of trenchfoot to rise in these units during the past weeks."
       
    At this time, each unit surgeon was required to furnish a report of these and other deficiencies to the commanding general of the division, who took the necessary corrective action. The result was a notable decrease in the incidence of trenchfoot.
 
SUMMARY
 
    It is evident, from what has been said in this chapter, that the causation of cold injury is an intricately woven fabric of agent, host, and environmental factors, and that no single one of the factor strands can be altered without influencing, or being influenced by, the other factor strands. The final design is an interaction and interrelationship of them all. One factor may predominate in influencing the incidence at one particular time. Then the situation may change, and another, or others, may gain in influence.


453  

    The various modifying factors described in the examples given were predominant for the periods selected, but no single factor could be completely divorced from all the others. In the absence of more precise data, however, and of more detailed observations, the examples do serve (1) to emphasize the roles of the various factors involved, and (2) to point up the need for further study, research, and evaluation of the influence and interrelationship of the several agent, host, and environmental factors responsible for cold trauma. The surveys which provided the data for these selected studies brought into play the principles of simple, sound field investigation.
       
    The data and examples thus secured provide a reasonable and convincing basis for concluding that cold trauma., as a component of mass trauma, behaves in accordance with the biologic principles and laws that govern disease or injury as a community problem. The specific causative agent in cold injury is cold, but, a number of modifying factors enter into its total causation. These can best be analyzed if they are divided into agent, host, and environmental factors. Studies of war records by theaters and units, and the reports of epidemiologic surveys by division in the European theater, demonstrated that epidemiologic behavior of cold trauma differs in only minor degrees from that of communicable disease.
       
    Evaluation of this experience has shown that the agent factors are cold and wet and that wet may be conceived of as having a synergistic relationship to cold. Host factors include status of individual training, fatigue, nutritional status, previous cold injury experience, inherent constitutional factors, psycho-social factors, and posture and dependency. Both the physical environment and the social environment are factors in the causation of cold injury. Physical environmental factors include weather (that is, temperature, precipitation, and wind), thawing, terrain, and altitude. Socioeconomic environmental factors include type of combat action, clothing supply and equipment, shelter, command leadership and attitude, training and experience, foot discipline, and rotation. Some of these are individual considerations and some apply to the unit. All of them entered into the total causation of cold injury in the European Theater of Operations in World War II, but it was only by assessing their individual weights by unit, by means of epidemiologic methods, that definitive preventive and control procedures could be applied.