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Scientists have long played a significant role in the evolution of warfare. This was certainly the case in World War II, which heralded the dawn of the atomic age. Thirty years before the first nuclear bomb fell on Hiroshima, Japan, however, science made one of its most consequential contributions to 20th century warfare with the introduction of poison gas.

The concept of chemical warfare long predated World War I. In the 5th century BC Spartan besiegers used smokescreens against defending Athenians. Leonardo da Vinci reconsidered the use of noxious gas in the 15th century. In the 19th century science fiction authors like H.G. Wells imagined gas warfare, even as military theorists pondered its applications on the battlefield. In the early 1800s chemists introduced chlorine and phosgene gas for industrial purposes—and developed masks to neutralize their effects. The technology for delivering chemical weapons on a large scale did not exist until around 1900, however, and its wartime use was prohibited by the Hague Conventions of 1899 and 1907—albeit without any provisions for enforcement.

At the outset of the war in 1914 scientists in France, Britain and Germany conceived various experimental weapons, including gas. British leaders hesitated to develop poison gas on moral and practical grounds until early 1915, when Maurice Hankey, secretary to the Committee of Imperial Defence, recommended the study of chemical warfare. The idea, he said, was to be prepared to retaliate should the Germans use it first. French officials, meanwhile, experimented with and field-tested tear gas.

The Germans were the first to take steps toward using gas at the front. German Chief of the General Staff Erich von Falkenhayn—later mastermind of the 1916 Battle of Verdun—convened a meeting of scientists in October 1914 to discuss gas and other experimental weapons. Later that month German artillery fired shells filled with of a form of sneezing gas on British troops at Neuve Chapelle, but the gas failed to disperse. After using tear gas with mixed results against the Russians in January 1915 and in the West shortly afterward, the Germans began experimenting with poison gas in hopes of achieving more decisive effects.

Chemist Fritz Haber (1868–1934), who would receive the Nobel Prize in chemistry in 1918 for his work in producing ammonia for fertilizer and explosives, pioneered the German development of poison gas. A Prussian of Jewish descent and a fervent patriot, Haber had been appointed director of the Kaiser Wilhelm Institute for Physical Chemistry and Electrochemistry in 1911. When the war began, he put the institute at the government’s disposal and worked to perfect the means of producing and dispersing poison gas, as well as methods to protect against it. The moral implications of his work did not concern Haber.

By early 1915 gas delivery via artillery shells had proven ineffective. Haber worked on new methods and hatched the idea of using fixed cylinders to release clouds of chlorine or phosgene gas. In theory the wind would carry the gas toward enemy troops, driving them from their trenches and rendering them defenseless against German attack. In reward for this innovation Haber received promotion from reserve NCO to army captain.

Many wartime military authorities balked at using poison gas, deeming it “unchivalrous.”But in January 1915 Falkhenhayn— backed by handpicked “experts” who declared that the gas cylinders did not violate the Hague Conventions—gave Haber the goahead for their production and implementation. The Germans chose the Belgian town of Ypres, where they had fought the British to a stalemate in 1914, for the initial use of the weapon. German troops emplaced thousands of gas cylinders there in March and April, rigged to release chlorine gas. Inklings of these preparations reached the Allies, but they took no precautions.

The Germans launched the first major poison gas attack near Ypres on April 22. French colonial troops were the victims. Two days later another gas attack hit Canadian troops who had just entered the trenches. On both occasions the Germans inflicted thousands of casualties and penetrated enemy lines but failed to achieve the hoped-for decisive results. Much the same pattern would follow as the war progressed. Following the initial German example, both sides used increasingly insidious varieties of poison gas and perfected methods of delivery.

Estimated casualties from poison gas in 1915–18 range from 500,000 to 650,000 on the Western Front, including some 73,000 Americans. Thousands more suffered on the Eastern Front and in the Middle East. Of the total casualties, about 75 percent came in 1918, after the Germans introduced mustard gas. The German decision to introduce poison gas helped define the World War I battlefield and inflicted incredible misery, but from a military perspective gas was next to useless. In World War II its use in the West was confined to the Nazi death camps.


Originally published in the March 2013 issue of Military History. To subscribe, click here.