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.