Successfull British attack during First World War. In order to allow a more general offensive, it was imperative that the Germans be driven off the Messines Ridge, which dominated the Ypres salient. Accordingly, after months of planning by General Sir Herbert Plumer 17-day bombardment began. At the end of the bombardment, mines containing 1 million pounds of high explosives were detonated under the ridge, ripping a hole in the landscape, as well as in the German lines. Plumer then ordered the advance, which successfully took the German position. Despite the huge damage inflicted by the mines, the German defenders still inflicted 17,000 casualties, although they themselves took 25,000. The victory allowed Haig to launch the Third Battle of Ypres. It also boasted morale at home, in a war where clear cut victories were rare.