During initial years of war Poland is occupied by

Poland was simultaneously invaded by Germany from the west on September 1, 1939 and by the Soviet Union from the east on September 17, 1939, as per the secret protocol of the Molotov-Ribbentrop Pact. The country was partitioned between these two powers and occupied by both throughout the initial years of WWII. Neither Russia (USSR) nor Germany alone occupied all of Poland - it was a joint occupation.