The Battle of Pilckem Ridge, 31 July – 2 August 1917, was the opening attack of the main part of the Third Battle of Ypres in the First World War. The British Fifth Army and Second Army and the French First Army on the northern flank, attacked the German 4th Army which defended the Western Front from Lille, to the Ypres Salient in Belgium and on to the North Sea coast. On 31 July the Anglo-French armies attacked the Ypres Salient and captured Pilckem (Flemish: Pilkem) Ridge and areas either side, the French attack being a great success. After several weeks of changeable weather, heavy rain began during the afternoon of 31 July. British observers in the XIX Corps area in the centre, lost sight of the troops that had advanced to the main objective at the green line and three reserve brigades