When British commander-in-chief, Douglas Haig, ordered a massive offensive in Flanders in July 1917, the British were riding the crest of a wave, having just captured the nearby Messines Ridge.
Haig believed that success at Passchendaele would not only enable the British to destroy German bases on the Belgian coast, but deliver a hammer blow to a reeling German army.
Instead, he instigated one of the most notorious episodes in British military history. Days of shelling merely alerted the Germans to the impending attack. Worse still, these combined with the heaviest rains in 30 years to turn the battlefield into a quagmire. Within days, mud was clogging up rifles, immobilising tanks and drowning men and horses.
Wave after wave of attacks made little progress until, in early November, Allied forces captured the village of Passchendaele. It was of little strategic significance but it gave Haig an opportunity to call of the offensive and hail it a success. Some 325,000 Allied casualties may have disagreed.