The Second Battle of Ypres was a battle of WWI fought from April 21 - May 25, 1915 for control of the strategic Flemish town of Ypres in western Belgium. 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 a European power (the German Empire) on European soil, in the Battle of St. Julien and the Battle of Kitcheners' Wood. By the end of the battle the Ypres Salient had been compressed and Ypres itself was closer to the line. The city was bombarded with observed artillery-fire and gradually demolished the city. 7,000 gas casualties were admitted to field ambulances and casualty clearing stations, and from May-June, 350 British deaths were recorded from gas poisoning. Both sides developed gas weapons and counter-measures which changed gas warfare to part of the structure of tactical attrition.