The German invasion began one week after the signing of what neutrality pact between Nazi Germany and the Soviet Union signed in Moscow on 23 August 1939?
Invasion of Poland: The Invasion of Poland, known in Poland as the September Campaign ("Kampania wrześniowa") or the 1939 Defensive War ("Wojna obronna 1939 roku"), and in Germany as the Poland Campaign ("Polenfeldzug") or "Fall Weiss" ("Case White"), was a joint invasion of Poland by Nazi Germany, the Soviet Union, the Free City of Danzig, and a small Slovak contingent, that marked the beginning of World War II. Invasion of Poland:  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-Tōgō agreement that terminated the Russian and Japanese hostilities in the east on 16 September. Molotov–Ribbentrop Pact: The Molotov–Ribbentrop Pact, also known as the Nazi–Soviet Pact, the German–Soviet Non-aggression Pact or the Nazi German-Soviet Pact of Aggression (officially: "Treaty of Non-aggression between Germany and the Union of Soviet Socialist Republics"), was a neutrality pact between Nazi Germany and the Soviet Union signed in Moscow on 23 August 1939 by foreign ministers Joachim von Ribbentrop and Vyacheslav Molotov, respectively.
Molotov–Ribbentrop Pact