The British and French high command had decided that a three prong attack on the German lines was necessary to break the stalemate that had ensued since the end of 1914. It was decided that the British forces would attack at the Ypres front as part of the three phase attack.
On July 18, the British and French artillery started a massive barrage on the German lines. On July 31, the attack was planned to take place. The battle itself was focused on the small town of Passchendaele. The ground on which the troops had to fight was getting increasingly muddy due to the artillery's destruction in the ancient drainage systems that kept the land dry. Soon, no man's land was like a giant mud puddle which in some places was so deep that men would vanish into it without a trace. However, the British high command was still insistant that the artillery had to be used in full scale barrage before the infantry could attack. They had learned nothing from the previous disasters at Ypres and the Somme, and once again, the artillery would play a large role in the failure of the offensive.
Early on the morning of the 31st, the infantry began its advance. Despite massive German counterattacks, the British managed to creep forward 2 miles. The battle was going well until the eve of August 1, when heavy rains began and flooded over the area even worse than before. The rain continued without stop for two weeks and the British army was heavily bogged down. However, the continued to press against the German lines. The Germans were also heavily bogged down which kept them from counterattacking but they still held a stubborn resistance. They hit the British with mustard gas and heavy machinegun fire, but the British still attacked relentlessly.
After a long, hard struggle, the Canadians took Passchendaele in early October. They then managed to push into Ghent bringing the offensive to a close with an overall cost of 250,000 casualties. There would not be another offensive at Ypres to follow.