The Hague Conference of 1899 was quite unequivocal in outlawing the use of chemical warfare on the battlefield or the Home Front:

  • Article 23: It is especially prohibited to employ poisons or poisonous gases.

Or more specifically:

Declaration II: On the use of projectiles the objective of which is the diffusing of asphyxiating or deleterious gases.

But hardly was the ink-dry when the signatories began to question the following:

  • Whether tear-gas was really a poison gas?
  • Was a hand grenade classifiable as a projectile?
  • Were irritant compounds included in the proscription?

With all such reservations apparently stilled, most of the putative belligerent nations began testing these products long before the Great War began. By the outbreak of the Great War, the British had in mind 50 potential toxic chemical warfare agents and the Germans over 70.

Once the Great War began all the belligerent nations field-tested toxic agents with various degrees of seriousness.

Initial field trials on Western Front of toxic products

October 1914. Although the Germans are usually given the dubious distinction of first using a poisonous product on the battlefield, in fact it was the French who, from August 1914, sporadically used their so-called cartouches suffocante (tear gas grenades) containing ethylbromacetate. These grenades were originally produced for the use of the French police in civil disturbances.

The Germans' first adventure into this field was in October 1914. An irritant substance that affected the skin and mucous membranes – dianisidine chlorosulphonate – was included in the shrapnel shells fired at the British lines at Neuve Chapelle. If there was any significant effect it was not officially recorded.

In January 1915, Dr Karl von Tappen, a chemist at the German War Ministry made a one-off proposal to the German Army of adding to artillery shells a tear gas (lacrymator), called xylyl bromide. This agent became known as 'T (for Tappen)-Stoff' and made von Tappen notorious internationally.

March 1915. The German T-shells were again used in March 1915, at Nieuport, on the Belgian coast against the French, improving efficacy by mixing in another toxic agent – bromacetone. But the exercise went largely unrecorded from the French side.

Up to this point the British had not deployed any toxic compound on the Western Front.

Large scale poison warfare with chlorine gas

From the outbreak of the Great War in August 1914, the reputed German chemist, Professor Fritz Haber, who can only been described as an evil genius and the principal instigator of mass toxic gas ware-fare, had been pestering the German High Command, led by General Eric von Falkenhayn, about the possibilities and advantages of gas war-fare. Haber was anxious to demonstrate on the battlefield, against Allied troops, a highly toxic product of a standard industrial chemical process – chlorine. When exposed to moist human tissue (skin, mucous membranes and, particularly, the lungs) the chlorine gas combined with body fluids to form hydrochloric acid; a highly caustic agent. Serious exposure to chlorine caused a painful death or seriously debilitating injuries, mainly of the eyes and lungs. Even light exposure caused almost immediate prostration and disablement.

It was envisaged that the liquidised chlorine would be fired in special artillery shells with a small amount of explosive acting as the dispersing agent. In this way a predetermined amount of the gas could be delivered in a given spot at an assured threshold of lethal concentration.

Haber, was convinced that this toxic gas attack would be a war-winning innovation, and bring fame and honours to him. The German High Command foresaw it a mass shock tactic that could provide the much-vaunted 'Breakout' from the closed confines of the trench complex that had burgeoned along the length of the Western Front. The German troops using the gas were to be protected by simple gas respirators.

A severe shortage of shells on the Western Front caused the Germans to make a revision in the plan. It was decided that the gas was to be dispensed from 190lb steel gas cylinders installed en masse in the German trenches to await a favourable wind towards the Allied Front Line. The wind had to be sufficiently strong to propel the gas cloud, but also light enough to maintain it at the minimum lethal concentration of 1,000 parts of the gas per 1,000,000 parts of air. So keen and anxious was Haber to see the operation set in train, he personally supervised, on site, the first deployment.

The chosen site was Langemarck in the Ypres Salient in Flanders where there were concentrations of French, British and Canadian troops.

On the 11th April 1915, the Germans opened the valves on the massed 6,000 gas cylinders releasing 160 tons of chlorine into a light breeze. The gas cloud flooded the trenches of the unsuspecting, and sparsely grouped, French Colonials and Territorials. In desperate panic they broke and fled to the rear causing a four-mile (seven-km) gap in the line. This violent evasive exercise, and their running along with the drift of the cloud, greatly exacerbated the effect of the gas. Whilst those who cowered, or collapsed, into the bottom of the trenches were engulfed with increasing concentrations of the gas as it settled.

Taking their opportunity, the Germans advanced into the vacated trenches, except on the flanks where British and Canadian troops, despite their own surprise, confusion and distress, largely held on and provided stiff resistance. This heroic resistance, along with the Germans' own nervousness about the effects of the gas, and the lack of ready reserves, took the edge of the German advance. Although a significant territorial gain was made, the German advance petered out and the Allied line was stabilised.

About 1,000 French died and another 2,000 showed symptoms of chlorine poisoning.

Haber was much depressed, as not only was the experiment far from an unqualified success, also the limitations of a wind-borne gas attack was self-evident. Particularly since most of the current German lines were situated up-wind of the prevailing wind. But it was equally clear that it was extremely difficult and hazardous for infantry to closely follow-up on a gas attack, even with the simple respirators with which most of the German troops were supplied. Collections of the gas lingered more than was anticipated.

However, having made the commitment to this kind of gas-warfare, the Germans persisted and launched further attacks on the Allies. The next was on the 24th April 1915 against the Canadians in the same Ypres sector, on the British in the MouseTrap Farm sector on the 2nd May and at Hill 60 on the 5th May.

Despite the lack of a formal effective defence against the gas, although local initiatives – particularly by the Canadians – had produced homemade cotton fabric facemasks, only the latter of these attacks was successful; and this was only possible after several further gas attacks.

Early gas defence measures

British: Despite a warning by German prisoners that the German Army was experimenting with gas war-fare, and the known fact that gas respirators had been issued to some German Army units, British Intelligence failed to follow-up the warnings.

Consequently, post the events at the Ypres Salient, panic and confusion ensued within the Allied commands. Whilst those in the trenches with a basic understanding of chemistry could see that a mouth and nose covered with moistened piece of porous fabric could filter out most of the unknown gas (and acted accordingly), this was by no means universally appreciated by the soldiery.

The British General Headquarters of the British Expeditionary Force (BEF) issued instructions on the 23rd April 1916 that the German gas was probably chlorine. It recommended that cotton gauze field dressings could be used as emergency respirators by dampening them with a solution of bicarbonate of soda. In the absence of any bicarb., human urine or clean water could act as a somewhat less efficacious substitute. Once the instructions were received, many units made local arrangements and gauze/lint masks with tying tapes were soon widely available in the British Front–Line. Meanwhile, a newspaper campaign by the Daily Mail in the UK requesting that British women provide such home-made masks for the men at the Front, was largely futile as many masks were stuffed with cotton-wool that became impossible to breathe through when wet. Unfortunately, despite official orders to the contrary, some of these 30,000 defective masks got through to the troops in the Front-Line and a few of these ladies' good intentions turned to tragedy.

More formally, the British Secretary of State for War, General Horatio Kitchener

called on Professor John Haldane, an expert in the 'gas' field, and sent him, accompanied by another expert, to France to examine the situation. Haldane returned with a captured German respirator and a recommendation for a British version based on the so-called 'Hypo' formula: sodium hyposulphite (photographer's Hypo solution), sodium bicarbonate and glycerine. It was called the Black Veiling Respirator. In addition to the absorptive pad it had an eye-flap and two securing tapes. This simple respirator saved many lives in the later battles of the Second Ypres campaign, though regrettably there were still many accidental gassings and deaths.

The limitations of the Black Veiling Respirator, and other ad hoc respirators, focused British attentions on a more effective and operationally practical replacement. The result was the 'British Hypo Helmet' or, officially, the 'British Smoke Hood'. It had a wool flannel hood entirely soaked in the aforementioned Hypo solution. The hood fitted the head to the shoulders and had a mica window. By May 1915, it was distributed to the BEF at a rate of 1,000 per Division.

Ever cautious of further known, and unknown, poisons that the Germans might deploy, such as phosgene and hydrogen cyanide among the many potential candidates, the scientist sought out other solutions that could be used to impregnate the Hypo Helmet against these gases. The outcome was the cotton fabric 'P (or Phenate) Helmet' which was effective against both phosgene and hydrogen cyanide. (Here the additional protective solution was sodium phenate). It had two 'goggle type' glass eyepieces and a breathing tube for expelling the used carbon-dioxide rich air to which the sodium phenate reacted adversely. By November 1915, every British soldier in the BEF had a personal 'P Helmet' and was busy learning the complexities of its use in action. The official name for the 'P Helmet' was the 'Tube Helmet'.

At the same time, the British authorities rejected the proposal that a respirator be built based on a helmet connected to a portable box containing a filtration apparatus. It was considered as a too big a departure from the current standard manufacturing procedures.

French: The French Ministry of War immediately launched an investigation under the leadership of Dr André Kling, to identify the gas and formulate a design of a respirator based on a German version captured in the field. Within three days the first of 100,000 moisture-retaining gauze masks were on their way to the French Front Lines with instructions that front-line commanders should authorise further local purchases as required. On the 25th April 1915 the German toxic gas was identified, from captured German respirators, as chlorine. The neutraliser recommended to field commanders was based on the same Hypo solution formula. Subsequently, a million respirators were ordered for immediate distribution. Also, oxygen equipment, as used in the French mining industry, was despatched for the use of key military personnel at the Front

In late May 1915, the French adopted both the concepts of the British Black Veiling Respirator (called Le Compresse) and the Hypo Helmet. By late May they were issuing them to their Front-Line troops, reaching a total of one million by late summer.

The Gas-shell

After several of the foreseen incidents with the handling of gas clouds produced from cylinders, in which a total almost 2,000 German troops were adversely affected, in May 1915 the Germans decided to revert to their original idea of T-gas shells. They also considered other gaseous compounds: bromine (an irritant of the eyes and respiratory tract); chloromethyl-chloroformate (an irritant of the lungs and a lacrymator - tear gas) and bromacetone and bromethyl-ethylketone (both lacrymators).

The principle involved was to swamp the target area with large numbers of small volume gas shells with the idea of maintaining a high concentration of the toxic gas over given area for a protracted period of time. The scheme proved to be more successful than the gas cloud idea, and in June and July 1915 it was proven to be highly efficacious when used on the French Front during the Argonne Offensive.

The retaliation of the Allies

British: The British retaliation in kind to the German gas initiative at Ypres was remarkably swift and between late May and September 1915 four Special (Gas) Companies were formed from selected members of the Royal Engineers under the overall command of Major Charles H. Foulkes, R.E.

Despite the now known weakness of the gas cloud dispersion technique, it was decided that the British would follow the German methodology using chlorine dispensed from gas cylinders. Accordingly the commander of First Army, General Douglas Haig incorporated a gas attack in his plans for an attack at Loos. On the 25th September 1915, chlorine gas was released from 6,000 cylinders over a period of 40 minutes, augmented by a barrage of phosphorous smoke bombs launched from Stoke mortars. The idea was to confuse the Germans about the period of the dispersion of the toxic gas under the cover of the smoke. Despite an improper degree of dispersal and control of the gas, which also affected a part of the British front-line, the follow-up infantry attack was a tactical success and the British captured Loos. Problems were encountered in the deployment of both of the Hypo and P Helmets, and considerable confusion arose over distinguishing genuine and false gas casualties in the British troops.

Not withstanding the reservations about the efficacy of the gas cloud, and the practicality of the gas helmets, further less successful British gas attacks took place at Loos in September and October 1915.

Thus, the die was cast, for both of the warring sides and, almost overnight, gas warfare became a major factor in the battles on the Western Front.

By pure serendipity Major Foulkes came upon a factory in Calais on the French coast with the capability of producing phosgene gas, thus ensuring a ready made supply when the British decided to use this deadly toxic gas.

French: Independently, the French produced their own respirators – the so-called P (Polyvalent) Tampon – and toxic gases; the first of which was hydrogen cyanide. Similar problems in the adoption process and the efficacy of the new more complex respirators were encountered.

In October 1914 another respirator was authorised called the Tambuté or, more commonly, the Tampon T.

New toxic gases and counter measures in 1915/16

Germans: The first new German toxic gas was phosgene (carbon oxychloride) and was used in a more deadly combination (10 times as toxic) with chlorine (four parts chlorine to one part phosgene) against the British in the Ypres Sector in October 1915. Over 9,000 cylinders of chlorine/phosgene (nearly 180 tons) were discharged. Further attacks were launched in December 1915.

The Germans introduced a new respirator in late 1915 called the Gummimaske (Rubber mask). It took the form of a tightly fitting rubberised cotton fabric facemask to which was attached a muzzle-like discoid canister containing filters of chemicals that neutralised all the then current toxic gases. One key component was granulated wood charcoal and the others were specific anti-dote chemicals. The filters were removable and the potential existed for fitting different filters for any new gases that might be deployed by the enemy. Goggle-type celluloid eyepieces were sealed into the mask

British: The British soon retaliated with their own variable dosages of the gas mixture of chlorine and phosgene. This was also delivered by gas cylinders. The chronic shortage of artillery gas shells, combined with the personal preferences of the British commander of the Special (Gas) Companies, meant the British retained the use of gas cylinders longer than the other combatants.

At the Somme in July 1916, the British used smoke and toxic gas sporadically, along with a version of the French product Vincennite; called Jellite by the British (see French below). Gas bombs fired from Stokes mortars also featured strongly. The gas chloropicrin was also extensively used although it was subsequently found to be less effective than phosgene.

When hexamine was discovered to neutralise phosgene, the British evolved a new technique whereby P Helmets were dipped in a phenate/hexamine solution and the P Helmet was reactivated as the PH Helmet. (A version of this helmet called the PHG incorporated sponge rubber backed goggles). By early January 1916, special field units were actively pursuing the reactivation of the helmets with phenate/hexamine, so that by the start of the Battle of the Somme, in July 1916, all British front-line troops were so equipped. Unfortunately, the PH mask was not fully effective against high concentrations of phosgene.

French: French production facilities for chlorine were initially strictly limited and there was some reluctance about its use of due to fears about the civilian population in the Occupied Zone. Nevertheless, the production of phosgene gas was authorised in December 1915. These reservations about generalised gas warfare delayed French retaliation until 1916 when attacks against the Germans began in February and carried on throughout the year. The French use of modified artillery shells (75mm) began relatively early in 1916 and included the use of phosgene at Verdun in March 1916. The French also introduced the use Vincennite gas (a form of hydrogen cyanide) shells which remained a staple in their armamentarium throughout the Great War.

Further modifications were made in early 1916 to the Tampon T mask to protect against phosgene. Huge numbers of the Tampon T and TN masks were manufactured, including one version with goggle eyepieces; a total of 8 million were supplied to the Front.

The mostly deadly and pernicious toxic gas: Mustard

Germans: Early in 1917 German chemists retested a gas previously thought to be too inactive. It was a mixture of ethylene and sulphur chloride. The Germans called it Lost or Yellow Cross. The British named it Mustard Gas (it was a yellowish liquid and smelt of mustard but had no relationship with the plant or condiment) or Hun Stuff (HS) and the French called it Yperite.

The initial German attack of 50,000 Mustard Gas shells in the Ypres Sector in July 1917, and its subsequent use in later battles, produced thousands of British casualties. The majority presenting with a delayed reaction (2 to 24 hours) to the skin (mainly in the naturally moist areas of the body), the lungs and eyes; as witnessed by the famous images of lines of blinded men being led away from the battlefield. The latter condition often led to temporary or permanent blindness requiring hospitalisation. This was frequently of a lengthy duration The only available treatment was analgesics and applications of solutions of calcium hypochlorite (bleaching powder) to neutralise the deposits of residual Mustard. The strength of the Mustard Gas meant a little went a long way. One of its more evil aspects was its tendency to persist in the soil presenting long-term dangers: it made whole stretches of the battlefield No-go Areas for friend and enemy alike. Mustard Gas became the most feared gas on the Western Front with its victims often requiring long rehabilitation times and involving outcomes of permanent disability; 2% were invalided.

The limitations of the German Gummimaske became increasingly evident in 1917 and a leather mask (Ledermaske) was introduced in the summer of 1917. The filtration system was updated to cover the new gas combinations introduced by the Allies, and to combat the higher gas concentrations achieved by mass bombardments using gas projectors. Another filter change (the SE) occurred in May 1918 to give more protection against phosgene.

As it became increasing evident that the rapid removal of contaminated clothing was a major factor in reducing morbidity and mortality, decontamination squads were recruited and temporary paper clothing made available.

Observing British success with their simple Liven gas projector arrays, the Germans introduced, in late 1917, their own version with some success and these came to be widely used to deliver the unprecedented combinations of gas shells that were used in the German offensives of 1918. However, gradually the relentless counterattacks of the Allies in the latter half of 1918 took their toll, and gas shelling declined in quality and quantity.

British: As 1917 progressed, the British stuck to their preference for delivering their gas attacks as a cloud from steel cylinders, but varying the components used, such as chlorine+phosgene, chloropicrin+hydrogen sulphide and phosgene+chloropicrin. In the period June 1916 to November 1917 nearly 330 tons of toxic gases were released. Stokes Bombs were also widely used. In addition, the Livens Projector was increasingly deployed and anti-artillery battery fire became of increasing emphasis for the British gunners.

From mid-1917, the so-called British Gas Beam Attacks focused high concentrations of toxic gas clouds onto a small front and drove deep into German occupied territory. In 1918, such was the extent of the British releases of these gas clouds – literally by the trainload – toxic gas contamination even extended over the borders with Germany. However, despite the efforts of the Special (Gas) Companies, the ever improving organisation efficiency the British artillery meant it assumed an increasing importance in the placement of gas on the constantly changing battlefield. Gas shells routinely accounted for more than 50% of all shells fired by the British and, as mentioned above, many of them were used in highly effective artillery counter-barrage fire. However, it is interesting to note that the first Mustard Gas of British manufacture was only used in September 1918 (St. Quentin): all previous stocks had been captured from the Germans.

As far back as 1915, with the realisation that the PH-Helmet was only efficient at quite low concentrations of the gas (particularly phosgene), and only physically tolerable to wear for strictly limited periods, the British decided to take another look at the original proposal for a box respirator. The result was the British Large Box Respirator. The box contained granules of pumice soaked in sodium sulphate, bone charcoal and lime permanganate (the British could not obtain sufficient quantities of the more active wood charcoal as widely used by the Germans). The respirator was carried in a canvas haversack worn over the shoulder. The filter box was connected to the wearer's mouthpiece in the fabric facemask by a flexible rubber tube. The facemask was secured by elastic tapes. The eye-spaces in the mask were covered by sponge rubber goggles, The fabric of the facemask was steeped in a zinc-hexamine solution for additional protection. To facilitate the optimal use of the mouthpiece, a nose clip was also provided.

As the Large Box Respirator was considered too cumbersome for general trench use, its issue was confined to special units such as the Special Gas Companies. However, its successful adoption led to the introduction of the British (Small) Box Respirator, a version especially designed for the infantryman. The rubberised facemask had integral goggle-type eyepieces. After a short evaluation in the field, large orders were placed, and all the British Armies in the field were fully equipped by the beginning of 1917. The PH Helmet was retained as a reserve, or back up.

As for protective clothing against Mustard Gas, the British decided intensive training and strong discipline was the better option. However, some protective gloves and overalls were eventually supplied from the Spring of 1918 onwards.

When the Great War ended in November 1918, the British Special (Gas) Companies were planning even larger scale releases of gas clouds using the so-called Thermogenerator Grenades containing arsenic smoke, dropped from the air in huge numbers.

British toxic gas production was planned to triple in 1919. The USA was also gearing up for the production of huge quantities of Mustard Gas (200 tons per day) far exceeding the production potential of Germany's industry.

French: By late 1915 the French Tampon T mask was becoming ineffective against the increasing range of German gas shells and a full face mask with respirator pad and an single eyepiece (the M2) was adopted in February 1916. A modified M2 with two goggle-type eyepieces was also introduced in April 1916. A total of over six million M2s were provided over the next two years. Meanwhile, parallel development went on of a French version of the Large Box Respirator type (the Tissot 1917), that was intended specifically for machine gunners and artillery observers, and the ARS (Appareil respiratoire spécial 1917 – facemask, inclusive goggles and an integral discoid canister filter box.). The latter was intended for more general use. However, the ARS did not come into widespread use until May 1918.

The French authorities spent considerable time and effort in the evaluation and development of protective clothing against Mustard Gas and in late 1917 certain items such as overalls, boots and gloves became standard items of issue in the trenches.

An anti-mustard ointment was also issued to the troops for self treatment


At first sight, to the Germans, the toxic gas weapon must have been seen as a war winner: it must have seemed at the time to present an overwhelming challenge to the Allied troops packed into the confines of the trenches of the Western Front. However, this did not prove to be the case. Primarily because the Germans lost their initial advantage through hesitancy and a lack of an overwhelming follow-up of manpower. But it was also due to the extraordinary resourcefulness of the Allies in largely standing firm in their trenches under the initial onslaught. And then by their rapid and progressive development of counter-measures to such an extent that in the long term they actually proved to be more efficient than the Germans' own.

Nevertheless, the Germans never lost faith in the efficacy of toxic gas and were by far its most prolific user on the Western Front using about 70,000 tons compared with a combined total for the British, French and Americans of around 65,000 tons. However, when more open warfare resumed in late 1918, gas attacks of all kinds lost much of their efficacy.

In the final accounting, toxic gas proved to be a relatively low cause of military deaths (3% of one million gas casualties) falling well behind the awful toll of the artillery shell and the machine-gun. But there is little doubt that as far as the troops of the Western Front were concerned, it came top in the long list of the miseries-of-war. It was known, appropriately, to the British as the 'Frightfulness' and remained forever in their memory as a major cause of fear, distress and disability; as it did among all ranks of the combatant nations.

A propos which, it is perhaps significant that, apart from a few limited applications by a few rogue and despotic regimes across the Globe, toxic gas has been absent from the world's battlefields for almost 90 years.


Along with perhaps the First Battle of the Somme and the Gallipoli Campaign, the use of chemical warfare on the Western Front is one of the most written about subjects of the Great War. The literature is truly immense. However, detailed information about the actual apparatus used in waging this chemical warfare is more difficult to find. The reader interested in the minutiae of this, and other related subjects, is strongly recommended to a new reference book entitled, World War I Gas Warfare Tactics and Equipment (2007),by Simon Jones with detailed drawings by Richard Hook. It is published by Osprey Publishers as #150 in their Elite Series under ISBN 978 1 84603 151 9. This author found it most helpful in clarifying certain queries. However, any errors and omissions in this article are those of the author alone.

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