World War II invasion of Poland Molotov–Ribbentrop Pact Nazi Germany invaded Finland occupied and annexed the Baltic states parts of Romania invaded the Soviet Union Eastern Front Poland Soviet Union World War I
The Soviet Union entered World War II on 17 September 1939 with its invasion of Poland, in accordance with a secret protocol within the Molotov–Ribbentrop Pact with Nazi Germany. The Soviet Union later invaded Finland, and occupied and annexed the Baltic states, as well as parts of Romania. On 22 June 1941, Germany invaded the Soviet Union, opening the Eastern Front, the largest theater of World War II.
