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Chapter III





The gases used against American troops by the Central Powers may be classified according to their physiological action, as lacrymators (eye irritants and "tear gases"), sternutators (nasal irritants, "sneeze gases," "vomiting gases"), lung irritants (suffocants, respiratory irritants), and vesicants (skin irritants, escharotics).a

The lacrymators produced temporary blindness. Liberation of small quantities of a gas of this type made it impossible to carry on without wearing a mask. These gases, while not responsible for many evacuations to the rear, harassed troops engaged in close fighting or in manipulating guns. Practically all of the long list of lacrymators had a bromine base.

The sternutator gases or nasopharyngeal irritants were nonlethal. They were capable, however, of producing extreme irritation of the nose, throat, and eyes, caused severe headache and nausea. The symptoms were comparatively short in duration, and the gases were not effective when the mask was worn. The inhalation of these gases before the application of the mask made mask wearing very uncomfortable and was apt to cause its premature removal and thus to subject the wearer to the effects of more important gases which usually accompanied or immediately followed the use of the sternutators. This type of gas usually arrived in the nature of a surprise, since it was used in high explosive shells. Because of this it was difficult for the troops to recognize immediately the presence of the gas. A good example of this type of gas is diphenychlorarsine, which was long and extensively used at the front.

The suffocating gases were used to kill and contained the most deadly substances employed in chemical warfare. Severe edema of the lungs quickly followed their inhalation, and death from asphyxiation frequently resulted within a few hours. Gases of this character were rather quickly dissipated, however, and it was difficult for the enemy to maintain an effective concentration over a long period of time. Good mask discipline robbed these gases of most of their terror and placed heavy expense on the enemy when they were extensively used. The two gases of this group most widely employed along our front were phosgene and chloropicrin. Many combinations were made from these gases with other substances intended to assist them in their action.

Phosgene, a gas of high density, with an odor much like that of decaying hay or grain, is little, if at all, irritating to the eyes and has no irritant action on the skin. Its presence, therefore, was perceived with difficulty and men

a The classification employed by the British medical historians History of the Great War, Based on Official Documents. Medical Services. Diseases of the War, Volume II, Including the Medical Aspects of Aviation and Gas Warfare and Gas Poisoning in Tanks and Mines. London, His Majesty's Stationery Office; 1923, p.252) is as follows: (1) Acute lung irritants; (2) lacrymators; (3) direct poisons of the nervous system or paralysants; (4) sensory irritants of the eyes, nose, and upper respiratory passages (sternutators); vesicants. The paralysant group (hydrocyanic and and sulphuretted hydrogen) is not included in the classification followed in the present volume, since our troops were not subjected to these gases.


were gassed before they were aware of exposure. Chloropicrin requires a higher degree of concentration to cause a suffocative action than could readily be obtained in field use. It was frequently used in conjunction with phosgene, the enemy hoping that the prompt irritant effect of the chloropicrin would prevent the wearing of the gas mask, thus rendering the soldier an easy prev to the accompanying phosgene.

The vesicant type of gas made its appearance later than the others mentioned, but soon became the most important in gas warfare. It first came into prominence at Ypres on July 12, 1917, dichlorethylsulphide being the chemical used.1 It was called by the French soldiers "ypèrite," by the Italians "yprite," and by the British, "mustard gas." Gas-mask discipline offered ample protection to the eyes and lungs, but very important military results were obtained from skin burns which caused the evacuation of enormous numbers of casualties. The Central Powers considered dichlorethylsulphide their most pernicious gas, and the experience of the Allies certainly confirmed the opinion that it had won this place in military importance. This gas had many features which rendered it especially suitable. It was toxic in concentrations which could not be detected by the sense of smell; the person affected suffered no discomfort at the time of the exposure, and symptoms were not evident until many hours later. Mustard gas penetrated all clothing and was remarkably persistent on the earth or on foliage over which it had been scattered. These factors tended to increase its effectiveness; in addition to the physical action of the gas on the men themselves, the morale of troops was impaired.

Truly speaking, dichlorethylsulphide is not a gas, but a liquid, which slowly vaporizes, and is effective in either state. It volatilizes slowly at ordinary temperatures and dissociates only at high temperatures. This latter fact was taken advantage of in the treatment of contaminated clothing. Furthermore, it is readily oxidized by such substances as chlorine or bleaching powder, and these chemicals were used in purifying dugouts, trenches, and ground or foliage saturated with the gas.

The following toxic substances were most frequently used by the Germans in their chemical warfare: (1) Lacrymators: Benzylbromide. (2) Sternutators: Diphenylchlorarsine. (3) Lung irritants: Chlorine, phosgene, carbon oxychloride, chlormethylchlorformate, bromacetone, chloropicrin. (4) Vesicants: Dichlorethylsulphide, chlorarsines, bromoarsines.

This classification, while eminently practical and convenient, does not imply that some of the gases have no physiological action other than that of their group. This is not true. For instance, bromacetone and chloropicrin, when employed in concentrations too low to affect the lungs, are lacrymators.

In addition to the four groups mentioned, gas officers occasionally reported the use of substances which possessed some of the properties of both the suffocative and vesicant gases. The usual shell filling which produced this result was made of equal parts of ethyldichlorarsine and dichlormethylether. This combination caused a vesicant action of an important nature, if kept in contact with the skin, with the air excluded; under ordinary battle conditions, however, this seldom happened. These gases possessed the properties of the suffocative type to a greater degree though not so effective as phosgene and chloropicrin. Innumerable combinations of gases were encountered occasionally.


A complete list, in so far as is known, of the gases used by the enemy, includes the following: 2 Acrolein, allylisothiocyanate, arsenic trichloride, arsine, bromacetone, broniacetic ether, bromethylmethylketone, bromide of benzyl, bromide of xylyl, bromide of toluyl, bromine, carbon monoxide, carbonyl chloride (phosgene), chloracetone, chlorine, chloropicrin, cyanogen, dichlorethylsulphide (mustard gas), dichlormethylether, dimethylsulphate, diphenylchlorarsine, diphenylfluorarsine, ethyldichlorarsine, formaldehyde, hydrocyanic acid, hydrosulphuric acid, iodacetic ether, iodacetone, methylchlorsulphonic acid, monochlormethylchloroformate (palite), nitrogen peroxide, phenyl-carbylamine chloride, phosphine, phosphorus trichloride, sulphur dioxide, sulphur trioxide, and trichlormethylchloroformate (diphosgene or superpalite).

The first gases used by Germany during the war were liberated from charged cylinders secretly installed in their trenches,3 the success of such a gas attack depending upon a favorable wind which would carry the gas in high concentration slowly over the trenches of the unprotected allied troops. There is no record of the American Army having been exposed to any of the original types of cloud gas attacks from such cylinders.

This method was superseded by the projector attack and trench-mortar firing of gas projectiles.4 Projectors, during most of the war, were large, smooth-bore cylinders. They were built to receive large drums or bombs of about 18 c.m. diameter. Charges of explosives were put in the bottom of these cylinders and the bomb placed on top. The cylinders were placed in batteries of from six to nine and operated at an angle of 45° in a trench or in some special area that offered protection. Such a plant usually contained from 200 to 800 projectiles, and the batteries were fired by electricity. This permitted the simultaneous discharge of a vast amount of gas on a relatively small target at a range of from 1,000 to 1,500 meters. The gases so used were of the lung irritant type. A successful projector attack produced very serious results, and it could be carried out without much regard to wind direction and velocity. These bombs contained 50 per cent of their total weight in gas, as against 10 per cent in a gas shell. The great advantages were the cheap guns for the delivery of the gas and the enormous sudden concentration of the gas in a small area. Nevertheless, this method of using gas at a relatively short range necessitated great secrecy in installing the projector during the night and in getting off the attack before the allied air service located the line of projectors, else allied artillery would destroy the plant and liberate the gas among the enemy's own troops. Furthermore, the flash and noise produced usually gave the troops sufficient warning to put on masks. This method, at best, was limited to local uses and, although continued throughout the war, it became less and less frequent. During the late months of the war the enemy made an effort to improve this method by building rifled cylinders and giving the bomb more of a shell contour.4 This gave a slightly increased range, but did not greatly enlarge the scope of its usefulness.

Hand grenades were employed for delivering gas under certain conditions, but their use was so limited for this purpose that they did not account for many casualties.4


These methods all proved of relatively little importance however, as soon as the enemy discovered that gas could be better distributed by shells.

The innovation which placed gas warfare on a very important military plane was the building of the gas shell and the distribution of these shells by the use of artillery.5 When first employed by the enemy the shells carried only lacrymator substances. Lethal gases made their appearance in shell about the time of the first battle of the Somme, and this method of gas warfare rapidly developed until, at the close of the war, all types of gases were being used in gas shells, with many of them as a part of the filling in high-explosive shells. Distribution of gas in this manner on a given target was limited only by the number of guns available and the rapidity of their fire. This method of delivering gas was in very small degree limited by weather conditions and had the advantage of long range. It sometimes affected the territory even beyond the actual range of the artillery, since with a favorable wind a harmful concentra- tion of gas would float with the air currents well beyond the point of shell burst. Definite tactics were evolved with this use of gas, placing its employment on as definite a plane as were the tactical methods of other arms of the service. After the use of gas shells had been instituted, it was difficult for the troops attacked to determine during a bombardment whether only high explosives were being used or whether a gas attack as well had been launched. For this reason it compelled the wearing of gas masks by the troops as soon as they were subjected to an artillery attack, and this in itself greatly lessened their fighting efficiency.

Their shell were classified by the enemy as pure gas shell and high-explosive gas shell. The pure gas projectile was employed for its lethal and casualty-producing effect by gas alone, since the effect of detonation and fragmentation was very slight. Such shell, when filled with a lung-irritant gas, were marked with a green cross. Various combinations of these fillings were marked green cross 1, green cross 2, or green cross 3, according to the nature of the particular mixture in use. Commonly the suffocative types of shell fillings were referred to as green cross ammunition. 6

Pure gas shells containing dichlorethylsulphide were marked with a yellow cross, and sometimes less important vesicant types received a further mark of identification such as yellow cross 1. This was later changed to green cross 3, the filling then being ethyldichlorarsine and dichlormethylether, the mixture previously described. Gas shell containing lacrymators were indicated by lettering such as " T-Stoff," "K-Stoff," "C-Stoff," and "B-Stoff." 7

High-explosive gas shell usually contained the nasal irritants such as diphenylechlorarsine and were marked with a blue cross.6 There is reason to believe that very late in the war some mustard gas may have been fired in high-explosive shell. The blue cross shell not only produced a gas effect but also detonation and fragmentation to a marked degree. The amount of gas filling in such a shell was necessarily small, the enemy entertaining the hope that the accompanying high explosive would assist in propelling, vaporizing, and concealing the gas. The burst of this shell, unlike the pure gas shell, could not easily be differentiated from the ordinary high-explosive shell burst. 8

The enemy found the markings mentioned necessary to make it easy for the storage and for artillery troops which handled such ammunition and served the guns. Fortunately, the relationship of these marks to the shell contents


soon became known to the Allies. This proved of great value in quickly identifying the nature of gases employed in an attack, since unexploded shell or fragments of shell bearing these marks were found.

Among the tactical programs adopted by the enemy for the use of war gases under different conditions the following are examples:9

I. Counter battery fire and long-range fire (calibers, 77 mm., 105 mm., 150 mm.,howitzers, 10 cm. guns):
Explosive shell .................................... 20
Blue cross gas shell.............................. 70
Green cross gas shell.............................. 10

The 15 cm. guns constituting part of the long-range group were provided with high-explosive shell only. The rate of fire during the preparation for the attack for the 77 mm.guns was found to be one shot per minute per gun. 
II. Fire against infantry - creeping barrage (calibers, 77 mm., 105 mm., 150 mm., howitzers):
Explosive shell...............................................60
Blue cross gas shell................................................   30
Green cross gas shell...............................................10
The 210 mm. howitzers were provided with high-explosive shell only.
III. Fire against infantry-box barrage (calibers, 77 mm., 105 mm., and 10 cm. guns):
Explosive shell................................................  30
Blue cross gas shell...............................................  60
Green cross gas shell...............................................  10

Yellow cross gas does not appear in these orders, since the enemy never attacked immediately through an area that they had shelled with mustard gas.

Allied troops at points selected for attack by the enemy and the artillery supporting such allied troops were subjected, before the enemy infantry advance, to a gas attack with high-explosive shell containing blue cross substances, and this fire was immediately followed by green cross shell. Late in the war it very frequently happened that all areas lateral to the point of attack were neutralized by a saturating fire of yellow cross shell. Reserve troop concentrations in the rear of such points of attack, villages near the scene, roads, wooded areas, ravines, reverse slopes, and other strong points, not intended to be occupied by the enemy were also shelled with mustard gas. In some instances, when an enemy attack failed and an orderly retreat could be made, he used mustard gas to assist in covering the retreat. 10

Thus it can be seen to what extent gas could be used in open warfare and how extremely difficult it was for the medical officer to determine whether one gas or a combination of gases produced the casualties he was called upon to care for. The individual patient might have been exposed to all the gases used in such an operation, or, on the other hand, he might have been in a spot where there was a significant concentration of only one of the gases.

The persistent and insidious character of mustard gas made it effective for several days after the burst of the shell. It made a good weapon, therefore, against wooded areas, billeting spaces, roads, artillery and machine-gun positions, its well as all points of cover. According to the needs of the situation, yellow cross shell could be used for surprise burst of fire, for saturation shoots, or for the area shoot. The last method, when used against inexperienced troops, was apt to cause them to minimize the danger of such concentration.


This method of fire consisted in maintaining a low concentration of mustard vapor in a given locality by slow intermittent shooting directed at that area. Such regions would be fired on frequently enough to keep up a low vapor concentration for days and weeks at a time. The inconspicuous way in which these areas were planted and kept planted with mustard gas resulted in many casualties. Directions for such area shooting are known in one instance to have been as follows:

Seventy-seven millimeter guns; 100 rounds per hectare (approximately 2½ acres):
Target at 1,000 meters, 100 rounds.
Target at 5,000 meters, 125 rounds.
Target at 6,000 meters, 125 rounds.
Target at 7,000 meters, 150 rounds.

(1) Monthly Summary of Information, Gas Warfare (British), No. 1, July, 1917. S. S. 184. On file, Medical Division, Chemical Warfare Service.
(2) Warthin, Alfred Scott, and Weller, Carl Vernon: The Medical Aspects of Mustard-Gas Poisoning. C. V. Mosby Company, St. Louis, 1919, 21.
(3) Gilchrist, H. L., Col., M. C., U. S. A., and Church, J. R., Col., M. C., U. S. A. Report on Chemical Warfare in France, July 1, 1921, 155. On file, Medical Division, Chemical Warfare Service.
(4) Gas Warfare, Part 1. German Methods of Offense. Army War College, February, 1918, War Department Document No. 705, 11.
(5) Gilchrist and Church: Op. cit., 156.
(6) Chemical Warfare, Medical Aspects. War Department Chemical Warfare, Medical Division, Washington, D. C., November 1, 1922. On file, Medical Division, Chemical Warfare Service.
(7) Gas Warfare, Part I. German Methods of Offense. Army War College, February,1918, War Department Document No. 705, 53.
(8) Ibid., 91.
(9) Special Report from the Chief of the Medical Division of Chemical Warfare Service to the Surgeon General, U. S. A., April 13, 1923, 2-3. On file, Historical Division, S. G. O.
(10) Fries, Amos A., Brig. Gen., C. W. S., and West, Clarence J., Maj., C. W. S.: Chemical Warfare. McGraw-Hill Book Co. (Inc.), New York, 1921, 177.