In April 1915 the Second Battle of Ypres (Second Ypres) commenced (22nd of April – 25th of May 1915). This second attempt by the Germans to conquer Ypres is remembered for the first large-scale use of poisonous chlorine gas. Within only a couple of hours the German advance reached nearly as far as the Ieperlee-channel, pushing forward in a south-western direction (The gas-attack and the story behind it is explained very detailed by KEECH 2001, p. 30-56). Within the gained territory the Germans built an extensive and heavily fortified system of trenches.The opposing allied forces were located down the slope. Contemporary military records indicate that once again vast numbers of soldiers died, the estimated total reaching as high as 105,000. After this heavy combat the position of the front line stabilised and remained very much the same from 24th of May 1915 for the next two years to come. The soldiers entrenched themselves and fortified their positions. From there both sides continuously attempted to win ground but failed to consolidate the gained territory, leaving the situation more or less unchanged.