Molotov-Ribbentrop Pact

The Molotov-Ribbentrop Pact was a secret nonaggression pact signed between Germany and the Soviet Union in which they agreed to divide up Poland between them. It allowed Germany to invade Poland the next month, starting World War II. Several weeks later Soviet troops invaded from the east.

Hitler broke the pact in the summer of 1941, launching Operation Barbarossa (the invasion of the Soviet Union).