Christopher Nolan’s film Dunkirk inspired new attention to the famous evacuation by sea, in 1940, of four hundred thousand British troops under harrowing air attack. Had that evacuation failed, the United Kingdom would have been deprived of a land army to oppose Nazi Germany. But before Dunkirk, British and French troops fought desperate last stands in the channel ports of Calais and Boulogne that bought vital time for the evacuation in the Belgian Port. The situation grew so desperate at Boulogne that Allied destroyers were forced to blast their way into and back out of the harbor, using naval guns to duel with tanks, field guns and even snipers while evacuating panicky mobs of British soldiers.