2017 £2 The Great War 1917 PNCThe Great War dragged on into 1917. In spring, the Germans began to withdraw from the Somme to their strongly defensive Hindenburg Line, leading allied command to mistakenly believe the war was being won. Allied focus shifted to the north, with the aim of occupying Flanders and removing the Germans from the Belgian Coastline. To break out of the so called Ypres Salient, British forces first had to occupy the Messines ridge at the regions southern end.