Japan attacks the USA on 7 Dec 1941. For the next 6 months, they continue to have successful attacks. However, by the end of the battle for Guadalcanal in Feb 1943, they are completely on the defensive.
Allies turn the tide in the Atlantic, where initially German U-Boats harass freely convoys to supply Britain. The Kriegsmarine calls off their submarines. The route to bring American soldiers who will land on D-Day is clear.
Their attack on the Soviet Union having failed, the German Army suffers a series of counter-offensives on the Eastern Front. Hitler's constant orders to stand ground backfire, and the Wehrmacht's losses are huge as the Soviets advance West.
After a careful campaign of disinformation that throws the German defenders off-guard, the Western Allies finally land on Normandy. After fierce fighting, they establish a foothold in Europe. France is liberated.
The Western Allies secure supply routes that will allow them to enter Germany, and the Ardennes counter-offensive fails. The Red Army advances rapidly, and Stalin shows uses the war for Empire-building. The SS implements the Holocaust.
The Marines succeed in the "island hopping" strategy against suicidal resistance. The US Navy establishes supremacy, cutting off Japan. Re-capturing the Phillipines and Burma is costly, but now Japan is fully in the defensive.
In 1945, Germany is crumbly on both fronts. The Western Allies cross the Rhine and take most of Germany, while the Red Army quickly advances into Berlin. After Hitler's suicide, Germany surrenders and is divided among the allied powers.
Japan keeps continues its suicidal resistance, and invading it looks costly. After 2 atomic bombs, the Emperor intervenes and stops the War. Stalin grabs territory in East Asia. The War is over, and the Atomic Era and the Cold War start.
