The trench warfare of the Western Front encouraged the development of new weaponry to break the stalemate. Poison gas was one such development.

The first significant gas attack occurred at Ypres in April 1915, when the Germans released clouds of poisonous chlorine. The gas inflicted significant casualties among the British and Canadian forces at Ypres and caused widespread panic and confusion amongst the French colonial troops.

The chlorine was a strong irritant on the lungs, with prolonged exposure proving fatal. The immediate public outcry for retaliation resulted in quick adoption of defensive anti-gas measures including new companies of Royal Engineers responsible for offensive gas warfare.

Poison gas was initially released from cylinders, but this required ideal weather conditions and could be very risky. In the first British gas attack, at Loos in September 1915, much of the gas was blown back into the faces of the British troops. From 1916, gas was employed in shells instead, which allowed attacks from a much greater range.

Gases used included chlorine, mustard gas, bromine and phosgene, and the German Army was the most prolific user of gas warfare.

Gas did not prove as decisive a weapon as was anticipated but it was effective in clearing enemy forward positions. As a result, anti-gas measures became increasingly sophisticated. Primitive cotton face pads soaked in bicarbonate of soda were issued to troops in 1915, but by 1918 filter respirators using charcoal or chemicals to neutralise the gas were common.

The physical effects of gas were agonising and it remained a pervasive psychological weapon. Although only 3 per cent of gas casualties proved immediately fatal, hundreds of thousands of ex-soldiers continued to suffer for years after the war.

IN THE LATE AFTERNOON OF April 22, 1915, members of a special unit of the German Army opened the valves on more than 6000 steel cylinders arrayed in trenches along their defensive perimeter at Ypres, Belgium. Within 10 minutes, 160 tons of chlorine gas drifted over the opposing French trenches, engulfing all those downwind. Filled with pressurized liquid chlorine, the cylinders had been clandestinely installed by the Germans more than 3 weeks earlier. The order to release the gas was entrusted to German military meteorologists, who had carefully studied the area’s prevailing wind patterns. Disregarding intelligence reports about the strange cylinders prior to the attack, the French troops were totally unprepared for this new and horrifying weapon.1

The surprise use of chlorine gas allowed the Germans to rupture the French line along a 6-kilometer (3.7-mile) front, causing terror and forcing a panicked and chaotic retreat. Within a matter of minutes, this slow moving wall of gas killed more than 1000 French and Algerian soldiers, while wounding approximately 4000 more.2 A British soldier described the pandemonium that flowed from the front lines to the rear.

[I watched] figures running wildly in confusion over the fields. Greenish-gray clouds swept down upon them, turning yellow as they traveled over the country blasting everything they touched and shriveling up the vegetation. . . . Then there staggered into our midst French soldiers, blinded, coughing, chests heaving, faces an ugly purple color, lips speechless with agony, and behind them in the gas soaked trenches, we learned that they had left hundreds of dead and dying comrades.3

The German High Command sanctioned the use of gas in the hope that this new weapon would bring a decisive victory, breaking the enduring stalemate of trench warfare. However, their faith in this wonder weapon was limited. Surprised by the apparent success of the attack, and having no plan to send a large offensive force in after the gas, the Germans were unable to take advantage of the situation. Within days, both armies once again faced each other from the same opposing fortifications. The attack that spring day, nonetheless, marked a turning point in military history, as it is recognized as the first successful use of lethal chemical weapons on the battlefield.

Here, I offer a window into the first weapon of mass destruction (WMD) by charting the development and use of gas warfare during World War I. Defined today as “man-made, supertoxic chemicals that can be dispersed as a gas, vapor, liquid, aerosol (a suspension of microscopic droplets), or adsorbed onto a fine talcum-like powder to create ‘dusty’ agents,” chemical weapons remain a viable public health threat for civilians and soldiers across the globe.4 If, in the world since the attacks of September 11, 2001, the threat of terror weapons seems a ubiquitous part of the daily news and the term WMD is now as familiar to soccer moms as to beltway defense planners, it is important to remember that the medical and public health consequences of chemical weapons use are as real today as they were in 1915.5

Although chemical weapons killed proportionally few soldiers in World War I (1914–1918), the psychological damage from “gas fright” and the exposure of large numbers of soldiers, munitions workers, and civilians to chemical agents had significant public health consequences. Understanding the origins of chemical warfare during World War I and its emergence during that conflict as a physical and psychological threat to both military and civilian populations can provide historical insight into possible contemporary medical responses to this enduring and technologically pervasive threat.

THE MILITARIZATION OF ACADEMIC AND INDUSTRIAL CHEMISTRY

World War I had numerous causes, including colonial competition, economic rivalry, and various ideological and cultural clashes among the rising nation states of Europe. A complex and binding system of alliances among the Central Powers (Germany, Austria-Hungary, and Turkey) and the Allied Powers (Britain, France, Russia, and beginning in 1917, the United States) placed peace in a delicate balance. The tipping point came on June 28, 1914, with the assassination of Archduke Franz Ferdinand of Austria-Hungary by a Serbian national. This single act set off a chain of events that quickly plunged the world into a global war that eventually claimed between 9 million and 10 million lives and lasted 4 years.

The economic and industrial forces that altered the face of Europe during the first decade of the 20th century were also instrumental in creating many of the technological innovations driving the war. In time, tanks, submarines, and aircraft revolutionized how World War I was waged on land, sea, and in the air. Chemical weapons were another new marvel of the war, and their successful research, development, and deployment reflected the increasing sophistication of scientific and engineering practice. At the same time, physicians and medical researchers (some of whom worked to create these weapons) struggled to create adequate defensive systems and medical procedures to limit casualties. By the time of the armistice on November 11, 1918, the use of chemical weapons such as chlorine, phosgene, and mustard gas had resulted in more than 1.3 million casualties and approximately 90 000 deaths