The Second Battle of Ypres was fought from 22 April – 25 May 1915, during the First World War, for control of the tactically valuable high ground to the east and the south of the Flemish town of Ypres, in western Belgium. The First Battle of Ypres had been fought the previous autumn. The Second Battle of Ypres was the occasion of the first mass use by Germany of poison gas on the Western Front.