“The Second Battle of Ypres. April 22, 1915.”
On the evening of April 22, 1015, the Second Battle of Ypres (in Flanders, western Belgium) broke out when the Germans for the first time gassed French troops with Chlorine gas. Massive pulmonary, skin and ocular casualties occurred, leading to the use of Chlorine and Mustard gases by both sides for the remainder of the war.