The battle of Poelcappelle was the fourth of a series of “bite and hold” battles launched by General Herbert Plumer during the third battle of Ypres. The first three such battles (Menin Road Ridge, Polygon Ridge and Broodseinde) had each achieved their objectives, biting chunks out of the German line and then defending those gains against any counterattacks. Each of the attacks had been supported by a well directed artillery bombardment that had isolated the part of the German front line as well as by a creeping barrage that had protected the advancing soldiers. They had also taken place during a patch of dry weather.
On 7 October the rains returned. 25mm of rain fell over two days, onto already saturated ground, and in an area where constant fighting had destroyed the field drains. The resulting mud affected every aspect of the battle. Movement became difficult. The artillery bombardment, crucial for the success of the battle, was affected in two main ways. First off all the guns themselves required stable gun platforms, or their accuracy would be lost. The wet ground around Ypres no longer provided the required stability. Second, many shells simply disappeared into the mud, and either failed to explode or had much of the force of their explosion absorbed by the mud. Much of the German wire survived the British bombardment.
The attack at Poelcappelle failed to achieve its objectives. Some units did manage to advance a short distance, although in several cases were then forced to pull back later in the day. The Guards Division, attacking west of Poelcappelle, advanced furthest. The attack at Poelcappelle was followed by the two battles of Passchendaele (12 October and 26 October-10 November), which would become notorious and often give their name to the entire offensive.