 As a result, on August 23, 1939, the Soviet Union and Germany signed the Molotov–Ribbentrop Pact, which included a secret protocol whereby the independent countries of Finland, Estonia, Latvia, Lithuania, Poland and Romania were divided into spheres of interest of the parties.On September 1, barely a week after the pact had been signed, the partition of Poland commenced with the German invasion.The Soviet Union on September 17.