A strategically important town in Belgium, Ypres was the scene of almost constant fighting throughout the First World War and was the focus for three highly significant Western Front battles. During the First Battle of Ypres (October to November 1914), German forces attempted to outflank the British Expeditionary Force but were thwarted, at great cost, in their "race to the sea". The Second Battle of Ypres (April 1915), is notable for the German's use of poisonous gas to support the attempted breakthrough by the German Fourth Army. Despite initial German successes the line was eventually stabilised by British and Canadian units. The Third Battle of Ypres (31 July to 10 November 1917) was the major British offensive in Flanders in 1917.