<Tr> <Td_colspan="2"> Battles <Ul> <Li> Gravenstafel </Li> <Li> St. Julien </Li> <Li> Frezenberg </Li> <Li> Bellewaarde </Li> </Ul> </Td> </Tr> <Ul> <Li> Gravenstafel </Li> <Li> St. Julien </Li> <Li> Frezenberg </Li> <Li> Bellewaarde </Li> </Ul> <P> During World War I, the Second Battle of Ypres was fought from 22 April--25 May 1915 for control of the strategic Flemish town of Ypres in western Belgium after the First Battle of Ypres the previous autumn . It was 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 battles of St. Julien and Kitcheners' Wood, engagements during the battle). </P> <P> The battle consisted of six engagements: </P>

When did the second battle of ypres start