 The front line around Ypres had changed relatively little since the end of the Second Battle of Ypres ( 22 April – 25 May 1915 ) . The British held the city , while the Germans held the high ground of the Messines – Wytschaete Ridge to the south , the lower ridges to the east and the flat ground to the north . The Ypres front was a salient bulging into the German lines but was overlooked by German artillery observers on the higher ground . The British had little ground observation of the German rear areas and valleys east of the ridges . 
