World War 2 was a total war that engulfed the entire societies of the major warring nations. The Axis powers of Germany, Italy and Japan lost World War 2 for several reasons:
1. Germany's invasion of the Soviet Union (Operation Barbarossa) failed due to brutal German tactics, overstretched supply lines in the harsh Russian winter, and the Soviet Union's vast military-industrial capabilities and manpower reserves.
2. The Allied invasion of Italy in 1943 tied down German forces and showed the Soviets that the Western Allies were willing to directly engage Hitler's forces in Europe.
3. The massive Allied D-Day invasion of Normandy in June 1944 opened a second major front