1939 Invasion of Poland

Battle context

The invasion of Poland, launched by Nazi Germany on 1 September 1939 and joined by the Soviet Union on 17 September, marked the beginning of World War II. The attack was a joint operation involving Germany, the Slovak Republic, and the Soviet Union, coming one week after the signing of the Molotov–Ribbentrop Pact. Germany committed approximately two million troops against a Polish force of roughly one million. Polish casualties reached 874,700 against German losses of approximately 59,000. The campaign concluded on 6 October 1939 with Germany and the Soviet Union dividing the entirety of Polish territory under the German–Soviet Frontier Treaty, extinguishing Poland as an independent state. The invasion precipitated declarations of war by Britain and France against Germany, setting the broader European war in motion. Though U.S. combat involvement in World War II would not begin until 1941, the destruction of Poland established the strategic and political conditions that ultimately drew the United States into the conflict.