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Poison gases share with nuclear weapons various unhappy distinctions. They not only occupy a significant place in the defensive and offensive planning of nations, but for many years they have also threatened mankind’s future on an apocalyptic scale. Once unleashed, they are uncontrollable–indiscriminately killing both soldier and civilian.

Contrary to general belief, the combat use of asphyxiating, or at least irritating, gases did not begin with World War I. Leonardo da Vinci, for example, described the use of sulphur and arsenic dust as a fill for shells fired at naval targets. Going back quite a bit earlier in history, the Athenians and the Spartans used sulphur fumes in the 5th century bc when attacking fortified cities. The Germans, moreover, as early as 1762 used bombs that emitted asphyxiating fumes during the siege of the Austrian-held Silesian fortress of Schweidnitz.

Closer to our own time, however, Germany, along with Britain, France and Russia, entered the Hague Convention of 1899, which specifically prohibited ‘the use of projectiles the sole object of which is the diffusion of asphyxiating or deleterious gases. Between the time Britain entered this convention in 1907 and the outbreak of war in August of 1914, the British government decided that although a dual-purpose projectile containing an explosive charge and a tear gas would not violate the literal terms of the convention, it nevertheless was contrary to the convention’s spirit and thus would not be used by the British army or navy.

In contrast to the fair play attitude of the British, the Germans–and to a lesser extent the French–began to douse each other with tear gases almost as soon as the misery of trench warfare took hold on the Western Front late in 1914.

When the war began, the French had held a small supply of tear-gas cartridges and possibly some tear-gas hand grenades. That stockpile was depleted by the fall of 1914, and in November of that year a resupply order was placed. The resupply order came about despite the apparent fact that the tear gas had gone completely unnoticed by the Germans!

The Germans, in turn, first used an irritant on October 27, 1914, in the capture of Neuve Chappelle. That day, the Germans fired 3,000 rounds of 105mm howitzer projectiles filled with sneezing powder against some Indian troops and French cavalry. The shells contained shrapnel embedded in the sneezing powder. It was thought that the explosion would grind and disperse the irritant. In practice, the barrage was so ineffective that the French and British failed to realize that chemical munitions had been used until the fact was uncovered in a postwar investigation.

Meanwhile, on the Eastern Front, the Germans collected a stock of 18,000 T-Stoff tear-gas shells for use against the czar’s army at Bolymov as both an experiment in gas ammunition and to support an attack designed to improve the German position in that particular sector.

The result was another relatively harmless fiasco. The attack began on January 31, 1915, in extremely cold weather. Because of the cold, the T-Stoff fill for the shells failed to volatilize and disperse. Consequently, the anticipated results did not materialize, and the attack produced only a local improvement in the German tactical position.

The Germans, like the French, continued using tear gas in spite of unsatisfactory results. There is evidence, for instance, that in March 1915 tear gas was used to bombard the French at Verdun and at Nieuport. Again, the effects were so trivial that the gas went unnoticed.

At that point, one of the great chemists of the 20th century, Fritz Haber, a German reserve sergeant major of cavalry and artillery–and soon to be given an unheard-of direct promotion to captain–enters the narrative. Haber’s greatest scientific contribution, for which he won a Nobel Prize in chemistry, was the invention of a process for nitrogen fixation.

With respect to chemical munitions, Haber, as director of the Kaiser Wilhelm Institute for Physical Chemistry, knew of the T-Stoff projectile work that was being carried out among members of his staff.

He saw a test for those projectiles in December of 1914 and was convinced that the weapon was quite useless. With typical creative insight, he suggested to the supreme command that a barrage of gas rounds fired from trench mortars might be more effective. The army staff, however, told him that the production capacity needed for the proposed new ammunition was not available.

It then occurred to Haber that gas, particularly chlorine, discharged from cylinders, would form a cloud. Haber recognized from the outset that the gas cylinder-gas cloud combination had serious weaknesses and was less than the best choice for a delivery system.

As the chief of staff to the German Eighth Army on the Russian Front, Maj. Gen. Max Hoffman later would write: The digging in of the [gas] apparatus was very complicated, and at any moment there was the danger of the enemy noticing the work of digging in and by strong artillery fire destroying the apparatus, and the gas would stream out in our own trenches. Besides this, the weather conditions of our theatre of war were very unfavorable for such gas emission; in the East we required a West wind–in the West an East wind, but as on our front the wind was mostly contrary, the employment of this invention was rendered still more difficult.

In spite of such clearly unsatisfactory characteristics, the German army’s supreme command decided to proceed with the new weapon. The passage from tear gas to chlorine was not made without some soul-searching by the supreme command. Tear gas–and sneezing powder–could be viewed as non-asphyxiating and not deleterious (at least with respect to a long-term physical effect on its victims), and therefore not in violation of Germany’s obligation under the Hague Convention. Although chlorine unquestionably is an asphyxiant, the relevant provision in the convention was specifically limited to projectiles for diffusing the gas. Thus, Haber’s gas cloud proposal did not violate the express wording of the convention–it was not a projectile delivery system.

In any event, chlorine and commercial compressed gas tanks were at hand in Germany, and the combination could be made available quickly and in large quantities without significantly interfering with other war-production activity.

The important salient around Ypres in Flanders was chosen for Germany’s first essay with a weapon of mass destruction. There were other, potentially better sites, but the army commanders responsible for those locations all rejected the new weapon; only Duke Albrecht of Württemburg, commanding the Fourth Army before Ypres, agreed to its use. The choice of Ypres, almost through default, would not be a happy one for the Germans. The terrain, although generally flat, is replete with shallow undulations and valleys of not more than 10 meters in depth. That topography disrupted the progress of the gas cloud and created local gas concentrations that impeded the progress of the riflemen advancing behind the cloud, many of them not equipped with gas masks.

Perhaps Ypres’ worst feature for a gas-cloud attack was its unsatisfactory prevailing wind. Generally, the wind in Flanders blew from the Allied side of the line to the German side–the wrong way, obviously. A favorable wind speed, also an important consideration, was capriciously unpredictable across the salient’s front. Those considerations notwithstanding, work went forward.

The Ypres salient formed a V in which the apex pointed almost directly east, into the German lines. The city of Ypres was located about in the middle of the open gap between the two arms of the V, the arm that formed the northern flank being held by French Algerian and Belgian troops, who then joined near the apex of the V with the Canadian and British troops manning the southern flank.

The first gas batteries were dug in for use against the British occupying the southern flank as of March 10, 1915. The batteries, in general, were organized in banks of 10 commercial gas cylinders, each cylinder about 5 feet tall and weighing, when filled, approximately 190 pounds. Each bank of 10 cylinders, under the control of one German pioneer, was joined through a manifold to a single discharge pipe. Emplacing these batteries in the front line, without alerting the other side, was not a simple undertaking, but a strenuous task that involved a great deal of physical labor. Interestingly enough, the first gas casualties on the Western Front occurred among the Germans, who lost three soldiers to gas from cylinders ruptured by Allied shelling.

After the batteries were in place, it was decided that wind conditions and the ragged configuration of the front line in that sector made it unsuitable for a gas discharge. New batteries of gas cylinders then were dug in along the northern flank of the salient, the batteries being concentrated at Bixschoote, near the junction between the northern flank of the salient and the front north of Ypres, and at Poelkapelle, near the apex of the salient. On April 11, the batteries were in place on the north flank, ready to deliver about 150 tons of chlorine gas on order. An attack was planned to follow behind the gas cloud, along a southern axis to sweep across the base of the salient, with the Bixschoote-Poelkapelle front as the line of departure for the German assault force.

After several postponements, always awaiting suitable wind conditions, the attack finally was ordered at 5:30 p.m. on April 22, 1915. What followed staggers the imagination.

As seen by the Canadians, who stood to the right of the Algerians, two greenish-yellow clouds formed on the ground and spread laterally to form a terrifying single cloud of bluish white mist. Blown by light wind, the cloud moved down on the Algerian trenches. The Canadians noticed a peculiar odor, smarting eyes, a tingling sensation in the nose and throat, and heard a dull, confused murmuring underlying everything.

Soon, Algerian stragglers began to drift toward the rear, followed by horses and men pouring down the road and finally by mobs of Algerian infantry streaming across the fields, throwing away their rifles and even their tunics. One Algerian, frothing at the mouth, fell writhing at the feet of the British officer who tried to question him.

Sir John French, commander of the British Expeditionary Force, later said: What happened is practically indescribable. The effect of the gas was so overwhelming that the whole of the positions occupied by the French divisions was rendered incapable of any resistance. It was impossible at first to realize what had actually happened. Fumes and smoke obscured everything. Hundreds of men were thrown into a stupor, and after an hour the whole position had to be abandoned with fifty guns.

As seen by the Germans, the effects of the attack were horrible, the dead lying on their backs with clenched fists, the whole field bleached to a yellow color. The Germans advanced until dusk, when the assigned objectives for that day were reached. With the attack renewed on April 23, however, the Germans found Canadians filling the gap in the line left by the gassed Algerians during the preceding afternoon. Resistance was stiff, and, in classic Western Front style, the attack bogged down with no further significant gains. Poison gas was used five more times in this Second Battle of Ypres, but the Allied soldiers adapted well to the new weapon. When the gas cloud was low-lying, some would stand on a parapet to be able to breathe in the air above the lethal fog. Others soaked cloth in water and even in urine, and breathed through the cloth to prevent asphyxiation.

By April 26, Gas Masks, Type I, rather useless patches of blue flannel mouth covering, were being distributed to the Canadian and British troops in the line. Thus, almost within hours of its first use, the new weapon was well on its way to being checkmated.

For all their disadvantages, the ungainly German gas cylinders almost worked in that attack of April 22, 1915. Why were the Allies found in such a deplorably unprepared condition? The Allies had captured two German soldiers in Flanders, one on March 28 and the other on April 15. Both prisoners gave detailed information about the forthcoming gas attack, the prisoner taken on April 15 even having been captured with his respirator. There were quite a few other indications that a chemical attack was forthcoming, the most striking being the discovery on April 17, during a British attack from the salient’s southern flank, of German gas cylinders in position. Nothing was done; the cylinders were not even reported. Perhaps the idea of gas warfare still seemed so alien to Western tradition that the Allies simply could not believe it would happen.

As a result, by 7:30 in the evening, little stood between the Germans and victory. They had achieved their breakthrough on the Western Front, but, for reasons that still elude posterity, they failed to follow it up. The opportunity–and any future hope of using gas as a surprise weapon–passed them by.

The first round of lethal gas used at Ypres by the Germans led to further gas attacks by both the Germans and the British all the way through the Battle of the Argonne at the end of the war in 1918, when John J. Pershing’s American doughboys had to contend with German mustard gas.

This article was written by John P. Sinnott and originally published in the April 1994 issue of Military History magazine. For more great articles be sure to subscribe to Military History magazine today!