The Battle of Dunkirk, in May/June 1940, is remembered as a stunning defeat, yet a major victory as well. The Nazis had beaten back the Allies and pushed them across France to the northern port of Dunkirk. In the ultimate race against time, more than 300,000 Allied soldiers were daringly evacuated across the Channel. This moment of German aggression was used by Winston Churchill as a call to Franklin Roosevelt to enter the war. Now, historian Joshua...