A World Undone: The Story of the Great War, 1914 to 1918

by G.J. Meyer

Second Ypres began late on the afternoon of April 22 after forty-eight hours of the kind of intense artillery bombardment that everyone now knew to be the preamble to an infantry attack. This time, however, when the guns fell silent, they were followed not by waves of charging riflemen but by the opening of six thousand metal cylinders containing 168 tons of chlorine, a lethal heavier-than-air gas that stayed close to the ground as it was carried on the evening breeze toward the French lines. Chlorine had been chosen because it was readily available—the German chemical industry produced 85 percent of the world’s supply—and because of its effects: it destroys the ability of the lungs to absorb oxygen and causes its victims to drown, generally with excruciating slowness, in their own fluids.