The whole plan was built on a misunderstanding. Three days earlier, at the Battle of Poelcappelle, communications had collapsed in the rain, and General Plumer was told that II Anzac Corps had reached objectives it had never reached. He passed that error back to Field Marshal Haig. The line for 12 October was drawn from the line that existed on a staff officer's map, not the one that existed in the mud. By the time air reconnaissance corrected the picture, it was too late to alter the barrage or the unit orders. Major-General Andrew Russell of the New Zealand Division understood what this meant. His men would have to advance much further than the plan said, across ground the guns could not cover, into wire that had not been touched. The CRA reported that he could not guarantee adequate artillery support. The attack went ahead on schedule.

The New Zealanders came up the Wallemolen spur in the dark on the night of 11 October, picking their way along duckboard tracks while a German gas bombardment fell on Gravenstafel. High winds and heavy rain began at zero hour. Their creeping barrage, thin to begin with, dissolved as they advanced; the howitzer shells that should have cut the wire plunged into wet earth and detonated harmlessly somewhere below it. The men reached the German pillboxes at Bellevue and found the wire intact, belts of it deep, swept by machine-gun fire from the concrete boxes behind. Small parties cut their way through the first belt and were killed at the second. Others tried to outflank the boxes and died on the wire. By mid-morning, the survivors were ordered to dig in where they stood, on the open slope, in the rain, under the guns.

South of the New Zealanders, a party from the 10th Brigade of the 3rd Australian Division reached the pillbox at Crest Farm. The Germans inside surrendered. The Australians pushed on into the streets of Passchendaele village itself, the highest ground for miles, the entire object of three months of fighting. They did not have the men to hold it. German troops rallied and recaptured the pillbox; the small group in the village was cut off. Their comrades behind them, the 10th Brigade, had taken too many casualties to come forward. The 9th Brigade, who had pushed to the second objective, were exposed on both flanks and fell back through artillery, machine-gun, and sniper fire. The Germans reoccupied the village. In the evening, the New Zealand Division withdrew to the lower slopes of the Wallemolen spur, which is where they had started.

By nightfall, 845 New Zealanders had been killed or mortally wounded, and thousands more lay wounded across no-man's-land. Many of them drowned in shell-holes before stretcher-bearers could reach them. The historian Glyn Harper has written that more New Zealanders were killed or maimed in these few hours than on any other day in the nation's history. The 3rd Australian Division lost over 3,000. The 4th Division, supporting on the right, lost nearly as many. The German 195th Division was shattered too and had to be relieved. Two German divisions were diverted to Flanders to make up the losses. The British official accounts called the German casualties "extraordinarily high." The British losses for October 1917 were the third highest of the entire war, after the Somme and Arras. The line had not moved.

Most of the New Zealanders killed here have no known grave. The mud took them, and what the mud did not take, the next bombardment did. Their names are recorded a short distance away, at Tyne Cot, in a curved apse of stone built into the larger memorial wall. The inscription reads: Here are recorded the names of officers and men of New Zealand who fell in the Battle of Broodseinde and the First Battle of Passchendaele October 1917 and whose graves are known only unto God. Two Victoria Crosses were awarded for the day, one to Private Albert Halton of the King's Own and one, posthumously, to Captain Clarence Jeffries of the 34th Australian Battalion. The Canadian Corps relieved II Anzac on 18 October and began planning a fresh attack on the same ridge.