Second Battle of Ypres

The Second Battle of Ypres was a First World War battle fought for control of the strategic Flemish town of Ypres in western Belgium in the spring of 1915, following the First Battle of Ypres the previous autumn. It marked the first time that Germany used poison gas on a large scale on the Western Front. Additionally, the battle was the first time that a former colonial force (the 1st Canadian Division) defeated a major European power (the German Empire) on European soil, in the Battle of St. Julien-Kitcheners' Wood.

• http://en.wikipedia.org/wiki/Second Battle of Ypres