The Battle of the Atlantic — How the Allies Won the War

"The only thing that ever really frightened me during the war was the U-boat peril," wrote Winston Churchill in his monumental history of World War II. His fear was shared by many. The North Atlantic was arguably the true front of the war for Europe, and the stakes there were terrifyingly high. Had Germany succeeded in cutting off the supply of American ships, England might not have held out. In a cable to Churchill in May 1941, Franklin Roosevelt put it plainly, "I believe the outcome of this struggle is going to be decided in the Atlantic and unless Hitler can win there he cannot win anywhere in the world in the end."