Phosgene, introduced in late 1915, was nearly invisible and much more lethal than chlorine.
By 1917, chemical shells, projectors, and mortars could deposit dense gas barrages on enemy lines, or behind them on supply routes, reserve trenches, or gun batteries. Fighting on the Chemical Battlefieldĭeadlier gasses and more reliable delivery systems were introduced later in the war. The British responded with their own chlorine attacks in September 1915, during which a change in wind direction resulted in more than 2,000 British soldiers being gassed by their own chemicals. But the introduction of increasingly effective gas masks and other precautions helped counter the German advantage. With the introduction of poison gas, many contemporaries feared that the Germans had discovered a war-winning weapon. After several days of chaotic and brutal fighting, the Ypres position remained in Allied hands. The gas shocked but, while some troops fled in panic, the Canadians held their ground. With the wind blowing over the French and Canadian lines on 22 April, they released the gas, which cooled to a liquid and drifted over the battlefield in a lethal, green-yellow cloud. Results of Gas at YpresĪt Ypres, Belgium, the Germans had transported liquid chlorine gas to the front in large metal canisters. The first large-scale use of lethal poison gas on the battlefield was by the Germans on 22 April 1915 during the Battle of Second Ypres.
