A town in Belgium which is most famous for being the site of an extremely bloody battle in World War I. The second battle of Ypres, which took place from April 22 to May 25, 1915, saw the introduction of chemical warfare by the Germans, in the form of 5000 cylinders of toxic chlorine gas. The Allies promptly developed their own poison gas, and while it led to many gruesome deaths, never proved to be a decisive military tactic in this war.