Explanation: The Molotov-Ribbentrop Pact was a 'non-aggression' pact between the Soviet Union and Nazi Germany which outlined carving up Eastern Europe between the two polities. In accordance with the pact, the Soviet Union invaded Poland with Nazi Germany in 1939.
Soviet apologists often claim that it was 'just' a non-aggression pact, which raises the question why the fuck they were assisting Nazi Germany genocide Poland, and why the pact involved carving up the Baltic states. The Soviets would go on to supply Nazi Germany with important war materiel until 1941, when the Nazis invaded the Soviet Union.