5924336 Holding the line near Dickebush before our final assault on Messines Ridge 7 June 1917\' (b/w photo) by Unknown photographer, (20th century); National Army Museum, London; (add.info.: \'Holding the line near Dickebush before our final assault on Messines Ridge 7 June 1917\'. Stereoscopic photograph, World War One, Western Front (1914-1918), 1917. Messines Ridge, high ground within the Ypres Salient, was captured on 7 June 1917 in a well co-ordinated assault. It began with a week-long artillery barrage. Allied intelligence had provided the gunners with up-to-date plans of the German artillery positions and by the time of the infantry attack around 90 per cent of German guns in and around Messines had been knocked out. As the barrage lifted the German defenders moved into their front line trenches to await the usual infantry assault, but this time the British detonated several explosive mines that had been dug underneath the German lines. Thousands of Germans were killed and many more left disorientated. In the immediate aftermath of the explosions, infantry from three corps attacked covered by an artillery rolling barrage. Within a few hours all their objectives had been taken. One of 100 stereoscopic photographs associated with World War One.); by National Army Museum .