10–12 October 1917
In July 1917, Field Marshal Douglas Haig began the Third Battle of Ypres campaign, in an attempt to break out of the Ypres Salient. At the Battle of Messines the far side of the Messines Ridge had been captured down to the Oosttaverne Line and a substantial success gained in the subsequent Battle of Pilckem Ridge. At the Battle of Langemarck there was an advance of 1,500 yd (1,400 m) around Langemarck village by XIV Corps. In view of the failure of the British Fifth Army to advance on the Gheluvelt Plateau in August, Haig ordered that artillery reinforcements be added to the south-east along the higher ground of the Gheluvelt plateau, Broodseinde Ridge and the southern half of Passchendaele Ridge. The main offensive was switched to the British Second Army under command of General Herbert Plumer, who continued the evolution of bite-and-hold tactics that had been used in July and August.
The Second Army planned to attack with a succession of separate bodies of infantry, on narrower fronts, for about 800 yd (730 m) to the first objective, 500 yd (460 m) to the second objective and 300 yd (270 m) to the final objective. Pauses on successive objective lines would become longer and attacks would be protected by a bigger, deeper multi-layered creeping barrage. Standing barrages beyond the objective lines were to be fired during pauses for consolidation, to obstruct German counter-attacks into the captured area, which would be confronted by a series of defensive areas based on the British objective lines. The British infantry would be in communication with its artillery and have much more local support from the Royal Flying Corps (RFC). Beyond the "creeper", four heavy artillery counter-battery double groups, with 222 guns and howitzers, covered a 7,000 yd (6,400 m) front, ready to engage German guns with gas and high-explosive shell. Strictly limited advances using these methods, at the Battle of the Menin Road Ridge (20 September), Battle of Polygon Wood (26 September) and Battle of Broodseinde (4 October), had produced a 4,000 yd (3,700 m) advance in two weeks, inflicted many German casualties. The German high command had made several changes against the refined British attacking methods, all of which had failed.
In the lower ground west of the Passchendaele Ridge, three months of constant shelling had blocked the watercourses that normally provided drainage. On the night of 4 October, it began to rain and continued intermittently for the next three days. Much of the battlefield again became a quagmire, making movement extremely difficult. Had the German defence collapsed during the Battle of Poelcappelle on 9 October, the reserve brigades of II Anzac Corps were to have passed through later in the day, to continue the attack to the far side of Passchendaele village and the Goudberg spur to the north. On 7 October, this afternoon attack had been cancelled by Haig, because of the rain and the final details of the plan for the renewed attack of 12 October, were decided on the evening of 9 October. Plumer had received misleading information about the progress of the attack that day and believed that "a sufficiently good jumping-off line" had been achieved, passing the erroneous information back to Haig.[b] The decision was made to continue the offensive, to gain more favourable winter positions on higher ground, to assist the French with their attack due on 23 October (the Battle of La Malmaison) and to hold German troops in Flanders during the preparations for the Battle of Cambrai.