During World War II, the Soviet Union first signed the Molotov–Ribbentrop Pact with Nazi Germany in 1939, dividing Eastern Europe between them. This changed in 1941 when Germany invaded the USSR in Operation Barbarossa. Despite early defeats, the Soviets turned the tide with victories at Moscow and Stalingrad, eventually pushing German forces back across Eastern Europe. In May 1945, Soviet troops captured Berlin, ending the war in Europe.