1. By using convoys and new technology such as radar, the Allies were able to gain the upper hand in the Atlantic Ocean, which made it easier to get troops and supplies to Europe. The Allies then planned to invade France in order to free it from German control.
2. Victory in Europe was secured primarily by attrition aided significantly by Hitler's ill-fated decision to invade Russia on June 22, 1941. ... Africa and then up through Italy's boot before the final invasion at Normandy on June 6, 1944 ( D-Day) was largely a war of attrition.