One week after the Molotov–Ribbentrop Pact's signing, the partition of Poland commenced with the German invasion of western Poland, followed by the Soviet Union's invasion of Eastern Poland on September 17, which included coordination with German forces. Three Baltic States described by the Molotov–Ribbentrop Pact, Estonia, Latvia, and Lithuania, were given no choice but to sign a "Pact of defense and mutual assistance" which permitted the Soviet Union to station troops in them.