In the spring of 1944 Adolf Hitler firmly believed that the llies would invade the Continent via the beaches of Normandy Anti Nazi officers in German Intelligence ultimately persuaded him that Normandy would be a mere diversion assuring him that the real invasion would occur at Calais Their campaign of deception convinced Hitler to keep half of the German forces in northern France in Calais to defend against an attack that would never happen This misinformed decision ultimately cost Hitler the war