The Battle of Poelcappelle was fought in Flanders, Belgium, on 9 October 1917 by the British Second Army and Fifth Army against the German 4th Army, during the First World War. The battle marked the end of the string of highly successful British attacks in late September and early October, during the Third Battle of Ypres. Only the supporting attack in the north achieved a substantial advance. On the main front the German defences withstood the limited amount of artillery fire achieved by the British after the attack of 4 October. The ground along the main ridges had been severely damaged by shelling and rapidly deteriorated in the rains, which began again on 3 October, turning some areas back into swamps.