The Second Battle of Ypres was a battle of the First World War fought from 22 April – 25 May 1915 for control of the strategic Flemish town of Ypres in western Belgium, following the First Battle of Ypres the previous autumn. It marked the first mass use by Germany of poison gas on the Western Front. For the first time a former colonial force (the 1st Canadian Division) defeated that of a European power (the German Empire) on European soil, in the Battle of St.