On June 25, 1915, the German press publishes an official statement from the country’s war command addressing the German use of poison gas at the start of the Second Battle of Ypres two months earlier.

The German firing of more than 150 tons of lethal chlorine gas against two French colonial divisions at Ypres in Belgium on April 22, 1915, had shocked and horrified their Allied opponents in World War I and provoked angry outbursts against what was seen as inexcusable barbarism, even in the context of warfare. As Sir John French, commander in chief of the British Expeditionary Force (BEF), wrote heatedly of the German attacks at Ypres: “All the scientific resources of Germany have apparently been brought into play to produce a gas of so virulent and poisonous a nature that any human being brought into contact with it is first paralyzed and then meets with a lingering and agonizing death.”

The German statement of June 25, 1915, was a response to this outraged reaction by the Allies; they considered it hypocritical, claiming that their opponents–namely the French–had been manufacturing and employing gas in battle well before the Second Battle of Ypres. “For every one who has kept an unbiased judgment,” the statement began, “the official assertions of the strictly accurate and truthful German military administration will be sufficient to prove the prior use of asphyxiating gases by our opponents.” It went on to quote from a memorandum issued by the French War Ministry on February 21, 1915, containing instructions for using “these so-called shells with stupefying gases that are being manufactured by our central factories?[that] contain a fluid which streams forth after the explosion, in the form of vapors that irritate the eyes, nose, and throat.”

This memo, the Germans concluded, proved that “the French in their State workshops manufactured shells with asphyxiating gases fully half a year ago at least” and that they must have manufactured sufficient numbers for the War Ministry to issue directions on how to use the shells. “What hypocrisy when the same people grow indignant because the Germans much later followed them on the path they had pointed out!”

Though the French were, in fact, the first to employ gas during World War I–in August 1914 they used tear-gas grenades containing xylyl bromide to confront the initial German advance in Belgium and northeastern France–Germany was undoubtedly the first belligerent nation during the war to put serious thought and work into the development of chemical weapons that were not merely irritants, like xylyl bromide, but could be used in large quantities to inflict a major defeat on the enemy.

In addition to chlorine gas, first used to deadly effect by the Germans at Ypres, phosgene gas and mustard gas were also employed on the battlefields of World War I, mostly by Germany but also by Britain and France, who were forced to quickly catch up to the Germans in the realm of chemical-weapons technology. Though the psychological impact of poison gas was undoubtedly great, its actual impact on the war–like that of the tank–is debatable, due to the low rate of fatality associated with the gas attacks. In total, the war saw some 1.25 million gas casualties but only 91,000 deaths from gas poisoning, with over 50 percent of those fatalities suffered by the poorly equipped Russian army.