Why did Germany invade Poland on September 1, 1939?

Adolf Hitler’s decision to invade Poland on September 1, 1939, was driven by his determination to expand German territory and dominate the continent by force, despite the diplomatic efforts of Western powers to restrain him.12

Key factors leading to the invasion included:

• Territorial Demands: Hitler sought the return of the free city of Danzig to the Reich and the construction of an extraterritorial road and railway across the Polish Corridor to connect East Prussia with the rest of Germany.32
• The Nazi-Soviet Pact: To avoid a two-front war, Hitler secured the German-Soviet Nonaggression Pact in August 1939. A secret protocol within this agreement partitioned Poland between Germany and the Soviet Union, which Hitler believed would discourage Britain and France from honoring their military guarantees to Poland.314
• Rejection of Diplomacy: When the British and French refused to withdraw their support for Poland, Hitler remained committed to his expansionist goals, ultimately ordering the invasion after staging a border incident to justify the military action.312