The Invasion of Poland, also known as the September Campaign, or the 1939 Defensive War in Poland ( or Wojna obronna 1939 roku), and alternatively the Poland Campaign or Fall Weiss in Germany (Case White), was a joint invasion of Poland by Nazi Germany, the Free City of Danzig, the Soviet Union, and a small Slovak contingent, that marked the beginning of World War II in Europe. The German invasion began on 1 September 1939, one week after the signing of the Molotov–Ribbentrop Pact, while the Soviet invasion commenced on 17 September following the Molotov-Togo agreement that terminated the Russian and Japanese hostilities in the east on 16 September. The campaign ended on 6 October with Germany and the Soviet Union dividing and annexing the whole of Poland under the terms of the German-Soviet Frontier Treaty.