As a spring breeze wafted into his trench, commander Georges Lamour of the French 73rd infantry saw something almost surreal drift his way. A yellow-green cloud. He barely had time to react. "All my trenches are choked," Lamour cried into the field telephone to headquarters. "I am falling myself!" Foaming at the mouth, crazed and blinded, the French soldiers fled in all directions—sucking for oxygen, finding instead poison that seeped into body fluids and ate away at eyes, throat, and lungs. World War I, and warfare itself, were never the same. Chlorine gas—sent crawling in favorable winds over Flanders Fields from German positions—sowed terror and agony for the first time on April 22, 1915. The era of chemical weaponry had dawned.
Some 1,200 French soldiers were killed in the chaos of that first 5-minute gas attack and the fighting that followed. The first use by allied forces came in September, when the British unleashed poison gas on the Germans at the battle of Loos, just across from Ypres in northern France. Rival armies ultimately launched 146 gas attacks in Belgium, with Germany using 68,000 tons of gas to the Allies' 82,000 tons. The lethal power of more sophisticated gases increased the horror by the month, even as the improvement of gas mask designs required more and more poison to be deployed. The last gas attack came just three days before the armistice of Nov. 11, 1918. Historians estimate that more than 1 million soldiers were exposed to gas—and 90,000 killed, with survivors in many cases suffering from chronic bronchitis and pneumonia. Read more on the use of the gas.