This is an important reassessment of a critical period in the British Expeditionary Force's fight against the German armies invading France in 1940. On 25 May Lord Gort, the British commander, took the decision to move 5th Division north in order to plug a growing gap in his Army's eastern defences. Over the next three days the division fought a little-known engagement, the Battle of the Ypres-Comines Canal, to hold the Germans at bay while the rest of the BEF retreated towards Dunkirk.