The German-Soviet Non-Aggression Pact
While it might seem like Nazi Germany fought as a lone wolf, the country had actually singed a non-aggression pact with Russia before WWII started. This required both not to attack each other at any point in the coming decade.

The German Soviet Non Aggression Pact
Hitler wanted to use the pact to get into Poland with no roadblocks. While many thought Stalin would strike first, Hitler broke that back with the invasion of the Soviet Union in 1941. Russia immediately joined forces with the Allies, and pictured here is a Russian and American soldier working together.
