Third Battle of Ypres

The Third Battle of Ypres was a major battle of World War I. On 7 June 1917, at 3:10 AM, nearly a million pounds of British mines detonated. When the Fourth Doctor visited Maurice in Flanders the night before the battle, he stated that the explosion would be heard in London. (AUDIO: The Haunting of Malkin Place)

Behind the scenes
The Third Battle of Ypres is sometimes grouped into the Battle of Passchendaele as a result of the two towns being very close to each other. Fighting at Ypres during World War I is mentioned in the novel Illegal Alien, but as there has yet to be an "in-universe" connection made between the battles, there are two separate pages.

Technically, the events of 7 June 1917 in Flanders were the start of the, not the Third Battle of Ypres itself.