Why did Hitler invade Poland?

Hitler invaded Poland on September 1, 1939, due to a number of strategic, ideological, and political reasons. Firstly, Hitler was driven by his desire for territorial expansion and the pursuit of Lebensraum, or "living space," for the German people, which he articulated in his book "Mein Kampf." Poland was seen as a prime area for such expansion being directly to the east of Germany.

Secondly, the invasion was part of Hitler's broader plans to reassert Germany's dominance in Europe and undo the Treaty of Versailles' terms, which Germany considered humiliating and restrictive after World War I. Regaining lost territories and rebuilding Germany's military strength were central to Nazi policies.

Thirdly, there was an ideological aspect. The Nazi ideology considered Slavic people, including Poles, as inferior and thus sought to conquer these lands, repopulate them with ethnic Germans, and exploit the resources and labor.

Lastly, the invasion was facilitated by the Nazi-Soviet Non-Aggression Pact, signed in August 1939, in which Germany and the Soviet Union agreed not to attack each other and secretly divided Eastern Europe into spheres of influence. This agreement gave Hitler the confidence that the USSR would not interfere, and it lessened the threat of a two-front war.

These reasons culminated in the invasion, which marked the beginning of World War II as Britain and France declared war on Germany in response to this aggression.