War movies tend to depict the battles a nation wins—not the ones it loses. So with a blockbuster Hollywood movie on Dunkirk hitting the silver screen this July, one would think that Dunkirk was a British victory. In fact, Dunkirk was the climactic moment of one of the greatest military disasters in history. From May 26 to June 4, 1940, an army of more than three hundred thousand British soldiers was chased off the mainland of Europe, reduced to an exhausted mob clinging to a flotilla of rescue boats while leaving almost all of their weapons and equipment behind. The British Army was crippled for months. If the Royal Navy and Royal Air Force had failed, and the Germans had managed to conduct their own D-Day invasion of Britain, the outcome would have been certain.