POISON GAS WARFARE.—The use of poisonous gases in warfare, as started during the World War, was only made possible by modern progress in chemistry. From a purely objective point of view, and apart from all ethical considerations, it should be observed that fighting-men have, at some time or other, adopted any means of making war, however ruthless. Poisoned weapons and poisoned wells are as old as history. The ancient Greeks indeed used sulphur fumes, and the Byzantines “ Greek fire and in mediaeval sieges carcasses of dead animals were thrown over the defences from mangonels, in order that their putrefaction might spread disease. Underground warfare in all times has been marked by attempts to drive the enemy from his galleries with smoke and suffocating fumes. The usages of chivalry, while prescribing courtesy to prisoners, imposed no limit on means of destroying life. Only in the 18th century, when war in western Europe became a very formal affair, did a tendency appear to set such limits. Both Louis XIV. and Louis XV. declined the use of “ infernal liquids ” offered to them by chemists; Later the tendency to impose moral restrictions became more definite. Lord Dundonald’s proposal for the use of asphyxiating smoke-clouds at the siege of Sebastopol was rejected by the British Cabinet. In 1865 at ChâIons experiments with asphyxiating shells were made on dogs before Napoleon III., who stopped the trials and declared that such barbarous means of destruction would never be employed by the French army because they were against the “ law of nations.” In the S. African War of 1899-1902, the Boers thought they were justified in complaining of the injurious effects of the gases given off by the British high-explosive shells. It was only indirectly that the Hague Convention limited the use of gas. It forbade, by Art. 23 (e), the use of weapons calculated to cause unnecessary suffering; “ poison or poisoned weapons ” by Art. 23 (a). A separate declaration had, some years before (July 29 1899), forbidden the use of projectiles whose “ sole object it was (qui ont pour but unique) to spread deleterious or asphyxiating gases.” The method which actually arose in the World War—that of a fixed apparatus which propels liquid gas in a jet—had apparently not then been generally foreseen. If it had been, the use of poisonous gases would, no doubt, have been more explicitly forbidden.

It is one of the ironies of history that the first great war after the Hague Convention should have witnessed its entire uselessness to limit human suffering. Gases of a nature to cause lifelong injury, liquid fire, molten metal, burning phosphorus—all were employed with a prodigality limited only by the inventive powers of the combatants.

There was, of course, no objection to the use of gases and substances of the lachrymator class. The object of these is to cause temporary incapacity by violent smarting of the eyes, sneezing or retching, while the effect passes off when the subject is removed from the radius of action of the gas. Probably the earliest example of this class is the Chinese “ Stinkpot", and it is interesting to note that as the Chinese were before the Western nations in the use of gunpowder, so they also were in this early form of what, in the World War, came to be known as “ Chemical Warfare,” a term which in itself is really too wide for “ gas warfare,” since chemistry enters into explosives also.

At the time of the Russo-Japanese War the subject of lachrymators was taken up by the Japanese, and later by the British War Office. It was also investigated by the French for police purposes. The British experiments covered a wide range of compounds based mainly on iodine, bromine and picric acid. The chief subjects of inquiry were effectiveness, keeping qualities and the effect of the liquid on the container. Nothing very highly effective was found, and it appeared that most of the liquids required a container of lead, glass or porcelain, on account of their action on steel or cast iron. The experiments were dropped some years before the World War, probably because, in the kind of warfare that was then anticipated, it did not appear that there would be much use for lachrymators.

In 1913 the question was submitted again to the British War Office. The Hague Convention was always kept in view, and it was considered that the term “ deleterious ” applied only to gases which caused permanent harm. As one chemist pointed out, poisons were prohibited by the convention, but disagreeable fumes were not. A few experiments were made with compounds of the lachrymator class in shells, and the question remained alive until in Sept. 1914, after the outbreak of war, it was decided not to use chemical shell of this type for the British army or navy.

Quite early in the World War stories began to be current on each side of the employment of gas shells by the other. In Dec. 1914, upon a semi-official suggestion from the British G.H.Q. in France, a section of the War Office, working with Sir William Ramsay’s Chemical Sub-Committee of the Royal Society, took the question up again. By this time trench warfare was fairly established and the armies of both sides were immobilized in trenches, facing each other in some places at a distance of only a few yards. All possible means of trench fighting had to be considered, and among other things it was thought that, if a sufficient number of lachrymating grenades could be thrown from the British front trenches into those of the enemy, he might be forced to evacuate them temporarily, or might at least have his fighting power considerably reduced by being forced to the constant use of a protective mask.

In Jan. 1915, an idio-acetate compound was brought forward which caused such smarting of the eyes that it was impossible to remain in its neighbourhood. By that time catapults were available which could throw a 2-lb. projectile 200 yards, a distance which brought the enemy’s trenches within range in many parts of the line. A tinned iron cylindrical grenade was therefore designed to hold 2 lb. of liquid, which by means of a 5-second time-fuse and detonator was made to burst and distribute the lachrymator in a fine spray. The British War Office and G.H.Q. approved of this grenade, and the manufacture was put in hand. At the same time many other substances were considered, mostly lachrymators and sternutators. Some of these compounds appeared to be very effective under experimental conditions, but were not so in the field.

While these modest tentatives were proceeding, always within the limits laid down by the Convention and the Declaration, the first German gas attack took place on the Ypres front on April 22 1915. This immediately altered the whole situation, as it was obvious that in using chlorine—an asphyxiant—the Germans had transgressed, if not the letter of the Declaration and the Convention, certainly their spirit. Accounts of the sufferings of those who had been exposed without protection to this new form of attack roused great indignation, but its effectiveness could not be ignored, and after a few days it was decided by the British authorities that preparations at least must be made to reply to the German gas offensive in the same manner. The section of the War Office that had been dealing with lachrymating grenades was instructed to take up the question, and with the aid of two or three chemists of the highest standing a small council was formed which sat continuously to discuss ways and means and consulted all the most prominent chemists and manufacturers. It soon became evident that the Germans had employed chlorine gas discharged under pressure from cylinders placed in the front line of trenches. A rapid review of all possible means of reply showed that chlorine was the easiest gas to begin with, but the position of Great Britain in this matter was very different from that of Germany. For the ordinary processes of the dye industry, the Germans produced in peace-time very large quantities of liquid chlorine. In England only one or two firms produced it, and that in very small quantities. Moreover, the available containers for transport of the chlorine were not only very few but were much too bulky and heavy for use in the field. The problem therefore was twofold: first, to install apparatus for an enormously increased supply of liquid chlorine, and secondly to design and manufacture suitable cylinders or dischargers for its use in the field. In both cases many initial difficulties were encountered, which were overcome in due course, and on Sept. 25 1915, at Loos, the first British gas attack with chlorine took place.

Meanwhile a very large range of possible gases had been passed under review with the object of discovering substitutes for chlorine. Obviously the thing to aim at was something which was more directly lethal than chlorine, and at the same time would cause less suffering by its effects. It was also realized from the first that the discharge of gas from the front trenches necessitated waiting for suitable weather conditions, which was very inconvenient for the arrangement of tactical operations; and it appeared to be necessary to release the gas in the enemy’s lines, so as to be independent of wind, which could best be done from gun shells or trench-mortar bombs. The principle was approved and a new class of problems had now to be faced.

Effects of Gases.—At this point it will be convenient to consider the effects produced by different varieties of gases, and the methods of employing them.

When considered from the point of view of their physiological effect, war gases may be classed in two main divisions, (a) Lethal, and (b) Irritant. The lethals fall under the two heads: those whose action is instantaneous or practically so (specific), and those whose action is more or less delayed, and is generally of an asphyxiating character.

A gas is classed as immediately fatal when death follows exposure for a period of two minutes to a certain concentration (i.e. a certain proportion in the air breathed). A higher concentration may cause instantaneous death. The only known compounds which, in concentrations practically obtainable, produce immediate death, are those containing cyanogen. The chief disadvantage of these is that when the concentration is not sufficient to cause death they have no effect at all, or only temporary faintness, headache or heart trouble. The other lethal compounds may have immediate injurious effects, such as headache, nausea, etc., and in high concentrations may cause death in a short time. In concentrations which are not strong enough to kill, they may cause casualties, which have the disadvantage that as the action is delayed a man may be able to continue fighting for some time after exposure. Thus in the case of phosgene, a man who does not notice that he has been gassed may die suddenly as much as 48 hours later.

The irritant gases are divided into (a) Lachrymatory (affecting the eyes), (b) Sternutatory (causing sneezing), (c) Vesicatory (blistering).

Lachrymators, on account of the extreme sensitiveness of the eye, can produce an effect in extraordinarily weak concentrations, such as 1 in 1,000,000 parts, or even less. Protection can be given by well-fitting goggles, but goggles cannot be used when there is a chance of exposure to lethal gases, because they would interfere with the gas-mask. The presence of lachrymators therefore entails the wearing of the complete mask, with all its disadvantages. The principal bases for lachrymators are iodine and bromine.

The sternutators were originally considered from the point of view of putting a man temporarily out of action by a violent fit of sneezing. A more important use suggested itself later, namely, that a man could be prevented by sneezing from adjusting his gas-mask, and would thus be exposed to the action of lethal shell. Similarly, if a sternutator could be found to penetrate the gasmask it would be impossible for the wearer to keep it on. Early in the war there were many reports of the intended use by the Germans of red pepper and capsicine. Many experiments were tried by the British with capsicine and similar agents, but they did not give good results. In the summer of 1917 the Germans introduced shells filled with diphenyl-arsenious chloride (Blue Cross shell). They used a great many of these, especially on the French front, but not with any great success. In view of their effect on the wearing of the gas-mask, these irritants require further investigation.

Vesicants are only practicable when they act in vapour form. In that case they are by far the most effective of all the irritants, as they attack the skin and all the mucous surfaces. Those first considered were effective only when they reached the skin as liquids, a condition difficult to secure, and they were therefore dismissed. But the German “ mustard gas,” also known as Yellow Cross and Yperite (Sym. dichlordiethylsulphide), acting as a vapour, was immediately successful. It first appeared in July 1917. It attacked the skin through the clothing, causing burns and irritation which might last from a fortnight to two months. Acting on the eyes it caused blindness, usually temporary. Acting on the bronchial tubes it might cause bronchial pneumonia. It might affect the heart, and also the stomach, causing vomiting and diarrhoea. These effects were sufficiently serious, in view of the large numbers of casualties which were produced, although the proportion of fatal cases was small, being no more than about 3 %. In this connexion it should be noted that substances of the irritant class may also be lethal in high concentrations, i.e. in concentrations higher than those necessary to produce the characteristic temporary disablement.

A very important consideration in the use of gas is what is known as “ persistence.” Cylinder gas, travelling with the wind, is effective over a particular area only while it passes; but liquid gas splashed on the ground in minute particles from a shell, or left in the ground by the smothered burst of a shell, may be effective for some time, and gases are classed as of “ high persistence ” or “ low persistence ” according to the time during which their effect remains. This depends on the rate of evaporation. A strong lachrymator may be effective on the surface for perhaps twenty hours; other irritants, such as mustard gas, may remain effective for days in suitable meteorological conditions.

Left under the surface they may remain latent for still longer periods, and take effect when disturbed by digging. It will be understood at once that this is a question of great tactical importance. For instance, a bombardment with “ high-persistence ” shells of trenches shortly to be attacked would be an obvious mistake, since the attacking troops after capturing the trenches would not be able to occupy them. On the other hand, in a raid on trenches which it was not proposed to retain it would be correct to burst bombs of “ high-persistence ” gas in trenches and dug- outs. So also in using a gas barrage or in bombarding an area, high-persistence shells should not be used if it is intended shortly to attack over that ground. The use of vesicatory shells especially will deny a given area to both sides, or “ nullify ” it. Gas shell is now classified not according to its physiological effect, but according to tactical use, viz. as persistent or non-persistent, the former being used for neutralization (e.g. mustard gas) and the latter for surprise destructive bombardment (e.g. phosgene).

The questions may be asked—why use the irritant type of gases at all if lethals are available? and among the lethal gases, why not use only the most powerful, namely, those which produce immediate death? In both cases the answer is found in the question of quantity. The specific lethal gases will only produce their effect in very high concentrations, which means that a large number of shells must be used simultaneously over a certain area. Shells of other types, though they may not kill at once, will produce casualties in very much lower concentrations. The question of the number of shells to be fired to produce a given effect is of great importance, not merely from the point of view of expense and the call on manufacturing resources, but still more in the field, as regards the number of guns required to fire the shells, the exertion of the guns’ crews, and the question of transport. Again, an effective lachrymator will produce an atmosphere that cannot be endured in one-thousandth part of the concentration which the lethal shell would require for its purpose. This is a matter of great importance, especially in neutralizing enemy batteries. Lachrymators rather went out of fashion towards the end of the war, not only because the great munition efforts of both sides had produced an enormous quantity of lethal shell, but still more because the neutralizing effects and harassing effects which were their raison d’être could be obtained better by mustard gas.

Vesicating shells, which are of high persistence and whose effect is often delayed, are specially useful against targets behind the front line. Although a trench or strong point which it is intended physically to occupy cannot be subjected to mustard- gas bombardments, the use of this substance in combination with an attack round the flanks proved very valuable in reducing defences which could not have been carried either by assault or by explosive bombardments. The possibilities also of mustard- gas barrages in defence are very great. They should be used against communications, depots, railway stations, and especially staff offices, telephone exchanges and everything that affects the enemy’s organization. An entirely odourless vesicator and one which does not produce a smoke easily recognizable will be particularly effective in this way.

As a general rule both lethal and irritant shells should be used in scientific alternation. With lethals, of course, the object is to catch the enemy unprotected by his masks, and in order to get a good effect a large number of shells must be fired at once. Such effects may be specially aimed at when large numbers of troops are known to be concentrated in certain places, previous to an assault. But it is also an important object to force the enemy to wear masks as long as possible, not only to fatigue him, but to exhaust the protective powers of the mask. This can be effected with irritants, and after some hours of bombardment with these, fresh bursts of lethal shells may be tried.

Methods of Employment.—The study of the characteristics of gas-clouds is very complicated. The cloud may consist of true gas, or minute drops of liquid, or infinitesimally divided solid particles. The last are known as “ particulate clouds,” and in their behaviour resemble a colloid vapour. Their action has to be studied physically and electrically as well as chemically.

The production of cylinder clouds, of course, is simple. The critical temperature of the gas employed must be above normal temperature. The liquefied gas is filled into a cylinder with nozzle on the principle of a soda-water syphon. The cylinder placed in position in the trench, and the nozzle is provided with short length of pipe, which is placed on the ground in front of the trench, and ensures that the gas on issuing is well clear of it. The valve being opened, the liquefied gas is discharged with some force, and as its evaporation causes a fall of temperature a heavy cloud is formed which travels with the wind. The necessary density of cloud is obtained by opening simultaneously a sufficient number of cylinders per unit of length of trench, other cylinders being held in reserve to continue the discharge for the time considered necessary. At first the cylinders were placed in groups against the front wall of the trench. This method he the disadvantage that a cylinder might be burst at an inopportune time by an enemy shell, and later the Germans placed the cylinders under the floor of the trench, protected by sandbags etc., while the British placed theirs in chambers excavated some depth below the parapet.

The earliest cloud discharges lasted only twenty or thirty minutes, or at most an hour, the necessary concentration being calculated at ten tons of the chemical per km. of front attack per hour. By the end of 1916 the French were using 100 tons per km. per hour, and the emission was continued for three or four hours. In the course of 1918 the British Special Brigade was using 200 to 250 tons of gas per km. per hour, and keeping up the cloud for eight, ten or even fourteen hours. The transport of gas cylinders up to the front trenches was naturally extremely laborious. It was very difficult to avoid attracting the enemy’s attention to the carrying and emplacement of them and there was always the risk of cylinders being burst by the enemy’s shell. The results that were achieved under such conditions testify in the highest degree to the devotion and courage of the troops employed. The enormous discharges of 1918 were effected by loading the cylinders on trolleys and running them up to the front trenches on light railways just before they were to be used. The nozzles were opened by an electric device.

On the other hand the use of gas in shells presented all sorts of difficulties from the outset. It was first necessary to find gases that could withstand the shock of discharge from the gun and the effect of bursting the shell. Some of the most lethal gases could not be utilized because they were chemically unstable, an were liable to become decomposed into their constituent element by shock. The cyanide compounds were to some extent of the nature, so that the Germans never used them. The French discovered a stable cyanide compound in which they had considerable faith, and the British used them to a certain extent.

Some stable lethal gases were found in due course, in addition to the irritants, and a whole series of problems presented themselves. The first question was the possible effect of the gas on the material of the shell. Some gases, such as phosgene, had no action on steel or cast iron. Others required containers of lead or porcelain; the French had a very effective method of blowing a glass lining into shell. The methods of sealing the shells and of filling and closing them offered merely technical difficulties, though these were considerable. The most suitable means of opening the shell was the next question, which had to be first considered, and then practically tested. The first gas shell used by the Germans contained a large proportion of high explosive; it is not known whether the idea was to follow the Hague Declaration in that the sole purpose of the shell should not be to spread deleterious gases, or to have a “ double-purpose ” shell, destructive and toxic. The result, however, was to produce an inferior explosive shell while most of the gas was dissipated by the explosion.

The British efforts were directed at first to getting the maximum amount of gas into a shell and releasing it with as little disturbance as possible. The gas-cloud would issue in the form of an oblate spheroid which travelled down the wind, gradually enlarging and being diluted by the air. Without wind the gas would remain on the surface, settling down in trenches or depressions of the ground. For opening with the least amount of disturbance cast-iron shells were indicated, as they required practically no bursting charge; but cast-iron shells have the drawback that they hold much less liquid than steel shell, because the shell wall has to be very much thicker to resist the shock of discharge. It was eventually found that not only every gas but every nature and every calibre of shell required a different bursting charge, and sometimes a different explosive. These all had to be determined experimentally. Later it appeared that certain liquids required a more powerful burster in order that they might be distributed in a fine spray. When a solid was introduced, in the shape of diphenylchlorarsine, a still more powerful burster became necessary in order that the solid might be atomized and dispersed as a cloud. Thus the German 77-mm. shell contained only 125 gr. of this solid enclosed in a glass container, the space between the container and the shell being filled with 600 gr. of explosive.

While the output of chemical shells remained very small the question of cloud formation by lethal shells was of high importance. Not enough shells being available to charge the whole atmosphere over a certain area with a fatal concentration, it was necessary to rely on the effect of each individual shell cloud, which ought to pass over a man or group of men while still at full strength. With the very large quantities of shell that were available later this question was of less importance, as it became possible to produce and maintain very high concentrations over a given area or length of trench. This was facilitated by bringing the larger natures of shell into service, and also by the use of Stokes’ bombs and trench-mortar shells, but still more by the Livens projector.

Since gas shells were intended to be used without considering the direction of the wind, the possible effect of a bombardment on one’s own troops had to be considered, and a further range of experiments became necessary. The kind of precautions required are indicated in an extract from German Army Orders of June 30 1918:—

The following regulations for gas bombardment are made known.

Minimum distance of the objective from our first line:—

(1)          Wind normal or oblique towards the enemy: for all natures of gas shell the least distance must be 300 metres; below that distance projectiles fired short may fall in our lines. When the wind is steady and the ground favourable, this distance may be reduced if only a small number of projectiles are being fired.
(2)          Still weather, or wind normal or oblique towards our lines:—
(а)          Heavy bombardment (several thousand projectiles), ground favourable for the return of the gas towards our lines:—
Blue Cross shells (Diphenyldichlorarsine—sternutators) . . . 1.0 metres (offensive).
Blue Cross shells . . . 500 metres (defensive).
Green Cross shells (Trichlormethylchloroformate—lethal) . . . 1.0 metres.
Yellow Cross shells (Sym. dichlordiethylsulphide—vesicatory) ... 1.0 to 2,000 metres according to the number.
(б)          Light bombardments (some hundreds of projectiles), when our troops have been warned and the ground is favourable:—
Gas shells of all natures: 300 to 500 metres. These distances are given for general guidance; they may be reduced or increased according to local conditions.

The influence of the state of the atmosphere and ground conditions on the use of gas is naturally of great importance. The first consideration is the wind. Lethal shells will produce the best effect with a wind of three miles an hour or less; with a wind of over seven miles they cannot be used effectively. Lachrymators can be used in higher winds up to twelve miles, but with diminishing effect. Heavy rain destroys gas effect. Dry weather and a bright sun tend to dissipate the gas quickly. The most favourable atmospheric conditions are little or no wind, moist atmosphere, and no sun. The night usually offers the best conditions for gas. As regards the effect of ground, it will be obvious that anything which protects the gas from the effect of wind assists concentration. Hollow ground, valleys, woods, areas covered with undergrowth, and villages make therefore good targets.

Field Organization.—The earliest British experiments on a field scale were made with extemporized appliances on the nearest open ground to the source of production of gases under trial. Some experiments not involving danger were made on a ground that had been acquired for flame-projector and explosive trials at Wembley, and at the Clapham School of Trench Warfare, but it was soon evident that a properly organized experimental ground was essential, and after much search a site was found at Porton near Salisbury. Here trenches and dugouts were made, artillery ranges prepared, and gradually a complete installation provided of laboratories, mechanical workshops, magazines, filling-rooms, gas-chambers, etc. It was now possible to experiment on a really scientific basis, while the ground available gave space for trial of many other trench-warfare requirements, among which smoke and incendiary shells and light signals were of great importance. Porton thus became the headquarters of the practical study of gas warfare. The laboratory experiments there were confined, however, to examination of the results of trials. Other laboratory work was done at the Imperial College, at Cambridge and other universities, and in private laboratories.

The first British experiments with gas-projectors showed the difficulties that were likely to arise with defective apparatus, or from changes of wind in the trenches; and it was realized at once that, for the handling of the new weapon, it was necessary to have some chemists in the front line who should be trained in the handling of the material, and who could also advise the troops on the effects of it. The suggestion of raising a Chemical Corps was put forward and approved; and as a result all the universities were invited to nominate students of chemistry, while at the front chemists were withdrawn from the ranks for the new corps. This was the beginning of the Special Brigade R.E. in which a certain number of selected students and officers already serving were given commissions, while others were appointed as non-commissioned officers to give them the necessary authority and position.

A certain number of officers and men were also appointed to it who were not chemists but had experience at the front. Thus the officer commanding the Special Brigade suggested working the men at cylinder emplacements in the trenches in pairs; one a chemist and the other an old hand from the infantry. The importance of having trained scientific men in the brigade was shown by the number of valuable suggestions that emanated from the officers, as well as by their extraordinary keenness and effectiveness in the field. After a short time selected officers from the brigade were appointed as chemical advisers at headquarters of armies and corps, and a central laboratory at General Headquarters was started for examining enemy gas and anti-gas appliances and dealing with urgent problems.

Organization in England.—In June 1915, upon the formation of the British Ministry of Munitions, the personnel hitherto engaged on chemical warfare was transferred to the ministry. The time had come for rapid expansion, and a Trench Warfare Department was created by the minister which was responsible for both design and supply, not only of chemical war material but grenades, trench mortars and projectiles, smoke shells, signals and the countless other requirements that modern trench warfare had made necessary.

The staff, rudimentary hitherto, was increased in proportion to the requirements of experiment and manufacture, and a scientific advisory committee was formed of eminent specialists in chemistry, physics and physiology. This new department was unique in combining the functions of research, design and supply. The other departments of the ministry were concerned with supply only, in response to the demand of the War Office. It was decided after much discussion that this exception should be made for the Trench Warfare Department, because it was recognized that in dealing with so many entirely new products, the manufacture of most of which was attended by considerable danger, it was essential that the designers should be in the closest possible touch with the manufacturers, should be able to explain what was being aimed at, and should advise on difficulties as they arose. The resultant close contact enabled them also to modify their designs during manufacture when necessary; to take account of facilities for supply and manufacture; and to order supplies in advance as soon as a new production was foreseen.

There is no doubt that this was the right procedure, as was proved by the rate production up to the end of 1915. The weak points were that the department had to communicate with the front through the War Office, which caused delays and mistakes, and that defensive arrangements, the provision of gas masks, etc., so intimately connected with offensive research, remained with the War Office. But, for the rest, the department had only to obtain the approval of the War Office for new designs and material, with an indication of quantities to be provided, and could then make its own arrangements. To this, however, one very important exception had to be made; they were not allowed to design or manufacture gas shell, and as other branches were not in a position to design them this led to serious delays. These delays were accentuated by the fact that in 1915, when shells were scarce and the value of gas shell had not been proved, the authorities responsible for shell generally were very unwilling to allocate shells to gas.

Gas warfare both in France and Russia began with divided control, and as this gave very unsatisfactory results, in each country after some time a separate organization was formed with complete control of design and supply. In the autumn of 1916 for instance, when the British were scarcely beginning to produce gas shell, Russia with her poor manufacturing resources was already sending to the front a steady supply of 25,000 gas shells a week for field guns. The British on the other hand, having begun on the right path, had left it. Within the ministry, at the end of 1915, research and supply were separated. It was assumed that they would work together as closely as before; but in fact, the Supply Department immediately and inevitably drifted away, and not only lost the advantage of supervision by the designers, but began to research on its own account, thus causing overlapping and confusion. Early in 1916 a Department of Munition Design was formed, and the Trench Warfare Research Department passed under the control of that department. Their work was then much restricted, and was directed by a department which knew nothing of it, and which intervened between them and the War Office. The confusion and friction that followed had a serious effect both on progress and output.
In the summer of 1917 the large number of casualties caused by the German mustard-gas shells occasioned some anxiety on the British front, and it was asked why the British army had not something equally effective. The reason was that since 1915 research in irritants had been discouraged; and as the Chemical Research branch was not in direct touch with G.H.Q. the question had never been properly discussed. In the result, in Oct. 1917 the Chemical Warfare branch was reorganized and considerably expanded. It had more direct communication with the front, and the Defensive organization from the War Office was amalgamated with it. The Supply Department was however kept separate.

In April 1918 the Trench Warfare Supply Department was broken up. This was the opportunity to restore the supply of gas and gas shells to the Chemical Warfare branch, especially as they already had supply on the “ anti-gas ” side; but the manufacture of gas went to the Department of Explosives Supply, and the filling of shells and bombs to the Department of Gas Ammunition Filling. This continued until the Armistice.

Objects of Gas in Warfare.—It must be clearly recognized that in the use of gas a new weapon of war has been found, which supplements without displacing the existing arms. Explosive and shrapnel shell have their limits. A very small amount of cover will give entire protection against shrapnel, and deep dugouts will protect against the most powerful explosive shell. When the enemy has provided cover and such shell become ineffective, gas becomes effective. A gas heavier than air will settle in trenches and remain in them; it will drop down the approaches to the deepest dugouts and permeate them. According to the nature of the gas, whether lethal or irritant, the enemy, if unprovided with gas-masks, will then be either killed or driven up into the fresh air. In the latter case, he comes once more under the action of the ordinary artillery shell. If he has masks he can remain under cover, but the masks must be worn, not only until the bombardment stops, but afterwards until the shelter is cleared of gas.

In trenches also, and in the open, as long as there is gas, masks must be worn, and the troops fight under a heavy handicap. This condition may be kept up indefinitely with a slow bombardment of irritants and occasional bursts of lethals. In the case of a smoke-cloud discharged for eight or ten hours continuously the protection afforded by the mask with its refills will be exhausted, and the troops attacked have three alternatives: to counter-attack, which without prearrangement and the necessary supports is hopeless, to die at their posts, or to retire.

The effect of gas differs fundamentally from that of ordinary shell in its persistence. A bombardment with explosive shell is effective only while it lasts. The moment it is over troops can move freely over the area of bombardment. With gas, on the other hand, troops cannot cross the area without masks until the gas has been dissipated.

Again, a shrapnel bullet or splinter of explosive shell may hit or may miss; troops may pass through such a barrage with considerable losses, but still in sufficient numbers to attack. The gas cannot miss. If enough has been discharged over a certain area to give the necessary concentration, every man passing over that area without a mask will be affected.

In clearing up a captured line of trenches during an advance, gas bombs are most effective for bringing the enemy out of deep dugouts. For this purpose a non-lethal irritant of low persistence, which will penetrate the enemy’s mask, may be used.
There is also the question of the effect of gas behind the lines. Such a discharge of cloud-gas as has been described may travel for miles before it is sufficiently diluted to lose its destructive effect. A long-range bombardment of an artillery or engineer depot will make it impossible for some days to handle the material without good protection.

That gas shell had a real military value as compared with ordinary shell is proved by the fact that both combatants used them so freely in the last year of the World War. Thirty per cent of the total American casualties were caused by gas, and no estimate can even be attempted of the general loss of efficiency brought about by the necessity for wearing respirators. Sillevaerts gives the following German order for the proportion of different shells to be used in the bombardment before the attack on the Aisne on May 27 1918:—



Blue Cross

Green Cross

1. Counter-battery and long-range bombardment
2. Bombardment of infantry positions
(a) Moving barrage
(b) Back barrage








3 %





Experience showed also that batteries attacked by gas shell were generally put out of action for several days.

Future of Gas Warfare.—Such then is the new weapon. Its potency is undeniable, as is the fact that it is effective where other weapons fail. The question is, will its use be continued? The answer, from a military point of view, may be found in the fact that, if one belligerent uses gas and the other does not, the former will in all probability win. Since experience has shown that conventions made in peace-time are not always respected when war comes, the argument that no nation can allow its existence to depend on the security of a convention prohibiting the use of such a weapon, is even strengthened by the fact that, after the lessons of the World War, nobody in 1921 could predict what further chemical or physical developments scientific investigation might produce in the future. Great advances might well be made in the discovery of gases that would penetrate any mask hitherto designed, and in the utilization of them. The nation that cares for its safety must therefore keep pace with such discoveries and with the means of protection against them. To prevent the production and the study of toxic gases is impracticable, because many of them are either necessary elements or by-products of manufactures essential to modern industries in peace-time.

As for the ethical side of the question, it must be considered dispassionately. Every new means of warfare, intensifying its effectiveness, has caused an outcry when first introduced. Gas warfare, per se, is not necessarily or exceptionally cruel. For instance, if it were conducted on both sides with cyanides, successfully adapted to war purposes, the resultant deaths would be the most merciful that history has ever known. It is to be noted that in the World War less than 3% of the total gas casualties were deaths, whereas some 20 % of casualties due to other weapons resulted in death either on the field or in hospital. The use of gases may be guarded by future conventions so as to prevent unnecessary suffering, just as explosive bullets were barred. Thus chlorine might be forbidden, because there is no death more painful than that by suffocation. But the utmost that seems possible is to limit by convention the use of poison gases in such a way that a breach of the convention will not place the offending combatant in a definite position of superiority.

It is infinitely to be deplored that gas warfare was ever introduced. It certainly adds a new horror to war. It imposes fresh burdens on the soldiers, who may ultimately be forced to spend most of their time in gas masks, even when far behind the lines. The most terrible thing perhaps about it is that, since it is impossible to remove all non-combatants from a zone of war, and equally impossible to provide them with masks, thousands of them must inevitably perish. For this reason alone it would be well if gases were forbidden. To forbid them, however, is one thing; to prevent their use is another. And unless more effectual means than were within sight in 1921 can be devised to make this (or any other) form of warfare impossible, considerations of national security must inevitably prevail.

Gases used in the World War.—The following are some of the more important gases used during the World War:—

Cyanogen Compounds.—Effect, in concentrations of as much as I in 1,000, immediate death. In weak concentrations, giddiness, headache and pains about the heart, but ultimately complete recovery. Used by the French and the British in shells as a mixture of 50% hydrogen cyanide, with arsenic trichloride, stannic chloride and chloroform.

Chlorine.—Attacks the respiratory tracts, forming in contact with moisture hydrochloric acid which destroys the tissues. Has a reflex action on the system generally, causing vomiting and diarrhoea. In high concentration may cause immediate death by spasm of the glottis. Only used as cloud-gas from cylinders.

Phosgene (Carbonyl chloride).—A very dangerous gas because the effect is delayed, and the victim is often not aware that he has been gassed. May cause sudden death as much as 48 hours after exposure. Very much used both in shells, and with chlorine as cloud-gas.

Diphosgene (Trichlormethyl chloroformate).—Effect similar to that of phosgene. Much used in shells, both alone and with other gases.

Chloropicrin.—Acts on the respiratory system like chlorine but more strongly. Is also a lachrymator. Much used in shells generally in combination with other gases.

Bromine.—Action similar to that of chlorine. It can be used conveniently for gas-clouds on account of its high boiling-point, but it forms the basis of a large number of powerful lachrymators. It was much used by the Germans as a lachrymatory shell-filling in the form of benzyl or xylyl bromide and brominated ketones.

Ethyl iodoacetate.—British lachrymator. Very marked action on the eyes, ceasing the moment the neighbourhood of the gas is left. High persistence.

Bromacetone, Chloracetone and Brommethylethylketone.—Much used in shell. Powerful lachrymators, and asphyxiating or lethal in high concentrations. Moderate persistence.

Diphenylchloroarsine.—Solid, dispersed in clouds of fine particles. Cannot be kept out by ordinary masks. Powerful sternutator, producing also coughing and sickness; in strong concentration, causing insupportable headache. Much used in Blue Cross shells by the Germans.

Diphenylcyonoarsine.—Similar to diphenylchloroarsine, but with a more powerful action. It superseded the latter as a German Blue Cross filling.

Mustard Gas, Yperite, or Yellow Cross.—(Sym. dichlordiethylsulphide). Vesicant. Attacks the skin even through the clothing with a blistering or burning effect. Affects all the mucous surfaces. Acting on the eyes causes blindness, usually temporary. Acting on the respiratory tracts may cause death by bronchial pneumonia. In favourable weather remains effective for several days.

Livens Projectors.—The use of lethal-gas shells, which require a very high concentration, implies the necessity of bursting a large number of shells simultaneously along a given length of trench or over a given area. With artillery shell this necessitates a concentration of every available gun within range on the point of attack, and needs a certain amount of preliminary arrangements. With Stokes or  trench-mortar bombs whose contents are much larger, and especially with a Stokes gun which can be fired very rapidly, a smaller number of pieces can be used. But probably the most effective means of obtaining a high concentration was the projector devised by Captain Livens, R.E. This consisted originally in using an old gas cylinder, with its top cut off, as a mortar; a hole is dug in the ground and the projector placed in it, resting on the ground at an inclination of 45 degrees and pointing in the required direction; the breech of the cylinder is backed up with a strong base-plate about 12 in. square. The propelling charge is contained in a tin box placed at the bottom of the projector and divided into compartments; the propellent explosive is placed in the compartments in bags, the number of bags being varied according to the range required. The projectile is a steel drum with rounded ends, 21 in. in length and just fitting into the cylinder, which has a bore of 8 in.; within the drum is a central tube running down its length, about 1 in. in diameter, which contains the bursting charge. The projector is fired by an electric fuse, about 20 of them being connected up with an exploder. These 20 may all be placed side by side in the same trench, and will constitute a battery. By these means as many as 4,000 of these projectors have been placed in position behind the front trenches in a night and fired simultaneously. Naturally, neither range nor direction are very accurate, but they are sufficiently so to give a very high concentration of gas over a small area, in some cases sufficient to kill men even when wearing their respirators. These projectors proved so useful that they were employed also for incendiary and high-explosive charges, and were immediately copied by the Germans, who feared them more than any of the other chemical warfare methods of offence employed by the Allies.

Incendiary Materials.—The beginning of the war showed nothing particularly new or useful in the incendiary materials used by either side. Quite early in the war a German incendiary shell was found to contain white phosphorus and a very inflammable celluloid mixture. In England petrol bombs were tried and containers filled with rags soaked in petrol. The results were not important. Phosphorus by itself was not a reliable incendiary agent, though a shower of molten phosphorus descending from a shell burst in the air had a good moral effect.

The first demand for incendiary materials for the British army arose from the necessity of burning the long grass in No Man’s Land during the summer of 1915, to prevent the enemy from using it for cover. To meet this demand a small catapult grenade filled with phosphorus and petrol was supplied, it being found that a small addition of phosphorus gave a more certain ignition of the petrol. Phosphorus, however, was far more useful as a smoke-producer than as an incendiary. A very important advance was made when a method of utilizing thermit in shell was discovered. Thermit is a mixture of iron oxide and aluminium which when ignited by a suitable primer burns with an intense heat, which has been estimated at 54000 Fahrenheit. It is used commercially for welding, and has been used in the army for such purposes as destroying guns, a small quantity of it being placed in the bore and ignited; the result of this is to make the gun useless, as when the thermit cools it is found to be firmly welded to the surface of the bore.

The ordinary ignition, however, is too slow for the purpose of an incendiary shell. Experiments were made with special ignition powders in Stokes shells but without good result. In Jan. 1916, however, thermit was tried with a bursting charge of ophorite which gave excellent results, the thermit being instantly raised by the discharge to melting-point so that when the shell was burst in the air it let fall a shower of molten metal. Ophorite was an explosive that had recently been discovered by Professor Thorpe, which while less powerful than the ordinary high explosives, had the advantage that it could be fired by a fuse without a detonator.

Thermit employed in low-velocity projectiles such as Stokes gun shells became a very valuable incendiary agent; with artillery shells it was not so useful, as satisfactory ignition was difficult to obtain.

Experiments were also tried with fine coal-dust distributed in the air but the results were not practical.

Anti-gas Defences.—About the end of March 1915, in consequence of the increasing rumours that the Germans intended to use poison gases, the British War Office asked Sir William Ramsay’s committee to consider what gases might possibly be used, and what would be the best means of protection. Before the committee reported, the cloud attack of April 22 was made. The circumstances were explained to Sir William Ramsay by telephone, with the remark that the gas was probably chlorine, and the next morning he came to the War Office with several sample mouth-pads made of flannel or wool soaked in hyposulphite of soda. An appeal was made through the Press to British women to furnish 1,000,000 of them at once, and thanks to their response and the efforts of the Red Cross the necessary quantity came in two or three days, so that within a fortnight every man in the British army at the front was supplied with this form of respirator. Although rudimentary, it gave useful protection.

Meanwhile chemists and physicists were at work on both the French and British fronts investigating the facts and advising on temporary protection. The day after the first gas attack, instructions were issued to keep buckets of solution of bicarbonate of soda in the trenches; the men were to dip their handkerchiefs in the solution and tie them round their mouths in case of gas attack. More efficient respirators were considered, also the use of large fans for clearing the trenches of gas, and direct fighting of the cloud by spraying neutralizing agents into it. Thousands of Vermorel sprayers were sent out, for clearing trenches and dug- outs. The dispersal of clouds by shelling and by explosions was tried, also lighting fires in front of the trenches to heat the cloud and cause it to rise. None of these methods were really effective in stopping clouds, and attention was gradually concentrated on direct defence by masks.

The first improvement on the respirator, which was introduced in the War Office a few days after the attack, was known as the Smoke helmet or Hypo helmet, a kind of Balaklava helmet made of flannel or thin serge, covering the head loosely and reaching below the neck, round which it was tied. The eyepieces were made of mica. This helmet was impregnated with hyposulphite, soda and glycerine solution, and carried in a waterproof bag. It gave satisfactory results for some time. Pending the complete supply, the increasing use of lachrymating shells by the Germans gave rise in June to a demand for goggles.

During 1915 the helmet was improved by the introduction first of phenates to protect against phosgene (when it is called the P helmet) and later by the further addition of Hyomine (when it was called the P.H. helmet), to ensure protection against phosgene and prussic acid. A respiratory valve and mouth-tube was also inserted in the P. and P.H. helmets, and this added to their comfort and efficiency.

As the use of other gases was foreseen, such as phosgene and hydrocyanic acid, a more effective protection than could be put into cloth became necessary. Thus the “ box respirator ” type was developed, and gradually issued during 1916. The general type of these consisted of a mask or face-piece into which entered a flexible tube issuing from a metal container which held chemicals, through which the air was breathed. In the earlier patterns the air passed through the tube into the space between the mask and the face; but as it is very difficult to get the mask to make an airtight fit round the face, the tube was extended and ended in a mouth-piece which fitted closely to the lips, while the nostrils were closed by a nose-clip. The container and mask were carried in a knapsack. The mica eye-pieces were replaced by celluloid, and eventually by triplex glass, which does not splinter when broken and remains airtight.

The introduction of a container for the neutralizing and absorbing agents gave free scope to chemists to provide against all kinds of poison gas. In this connexion it is worth recording that the British gas-mask did in fact give efficient protection from its introduction to the end of the war.

The containers were filled with alternate layers of charcoal and composition granules. The charcoal absorbed gases, and the granules, whose composition could be varied indefinitely, absorbed and neutralized them. The container had the further advantage that its contents could easily be renewed.

This type of respirator continued in use until the end of the war but was subject to continual improvement. No effort in this direction could be spared seeing that any defect in the manufacture or adjustment of the mask might mean death to the wearer. Constant progress was made with the British and French patterns, and the Americans when they entered the war took up the question very thoroughly. They, like the French, had the advantage that their chemical service was a separate branch of the army with the offensive and defensive sections working under the same head. Among other defects the air-tight fitting of the mask to the face needed a great deal of study and experiment. The eye-pieces gave trouble because moisture would condense on them both outside and using a soapy solution on the glass. The whole apparatus had to be made as little cumbrous as possible, and so adjusted with its in. This was partly cured by using a soapy solution on the glass. The whole apparatus had to be made as little cumbrous as possible, and so adjusted with its knapsack that it could be very quickly taken out and put on. The use of the mouth-piece and nose-clip was very trying when worn for long periods.

In 1918, the Tisset mask was introduced in France, which did away with the mouth-piece and met the difficulty of condensation by causing the cold air from the inlet-tube to pass across the eye-piece in entering the mask. This type, which was adopted and improved by the Americans, was known as a “ single-protection ” respirator. Its weak point is that if the face-piece is torn, or does not fit properly, protection is lost.

The provision of the charcoal for the containers opened up a wide field of investigation. For absorbent purposes a very dense charcoal was required. Experiments made in the United States showed that coconut-shells gave the best form of charcoal for the purpose, but their preparations were on such an extensive scale that they calculated that they would require a supply of 400,000 tons per day of coconut-shell, which were obviously not obtainable. After coconut-shells the best carbon was obtained from fruit- stones such as peach, cherry, etc., and Brazil and other nutshells. Carbon obtained from hard wood, such, as the ironwood was of less efficiency.

The scale on which the United States worked is shown by the following figures given by Farrow of the production of protective materials up to the date of the Armistice, the great bulk of which were produced in the last four months of the war:—


            Production up to Nov. 11 1918



Extra canisters


Horse masks


Bleaching powder (tons)


Extra anti-dimming (tubes)


Sag paste (tons)


Dugout blanket oil (gallons)


Protective suits


Protective gloves


Dugout blankets


Warning devices


Trench fans


The sag paste mentioned in this list was an ointment used for the skin to protect it against mustard gas, the protective suits and gloves being for the same purpose. The blankets, which were to seal the doors of dugouts, were made of specially woven cotton treated with a specially heavy oil. The warning devices were mainly watchmen’s rattles and Klaxon horns.

From the beginning gas schools were established on all army fronts, where men were taught the use of the masks and made to enter gas chambers with masks on to get proof of the protection afforded. Similar schools were established by all the nations at their gas defence headquarters, where experiments could be tried. The result of such work is well shown by the following extract from
Farrow’s description of the American gas service:—

“ There was a special field-testing section of the Gas Defence Division composed of about 150 men who were trained to the minute in field manoeuvres and did most of their work in gas-masks. They were constantly in and out of gas with regular production and experimental masks. They played baseball in them, they dug trenches, laid out wire, cut wires, and fought sham battles at night, both with and without actual gas. The work of this section even went so far in the case of the later design as to include a test where six men worked, played and slept in the masks for an entire week, only taking them off for 30 minutes at each meal-time, and each day entering high concentrations of the most deadly gases without any ill effects whatsoever to the wearers. When it is remembered that eight hours was the limit of time which a strong man could wear the old-type mask, something of the efficiency of the new mask may be realized.”

These of course are experimental results with selected men, which generally differ widely from those obtainable in the field. They only show the great improvement made in patterns of respirators before the end of the war. The fact remains that any efficient respirator is a source of fatigue as well as a great inconvenience. British experiments have shown that in hill-climbing with and without respirators, there is a marked difference in the increase of heart rates and rates of breathing under the former condition. Up to 1921 what had been done gave good protection with reduced inconvenience. But much remained to be done; and indeed complete protection both in the front and rear areas might be unattainable.  (L. J.)