Adolf Hitler Why Germany Invaded Poland

Adolf Hitler – speech to the German Reichstag- September 1, 1939
For months a problem has tormented all of us. Long ago the Diktat of Versailles bestowed this problem on us. In its depravity and degeneracy it has now become insufferable. Danzig was a German city and is a German city! The Corridor was German and is German! These regions owe their cultural development exclusively to the German Volk. Without this Volk, these eastern regions would still be plunged in the depths of barbarism.
Danzig was torn from us! Poland annexed the Corridor! The German minorities living there are being persecuted in the vilest manner imaginable. In the years 1919 and 1920 over one million men of German blood were forced to leave their homeland.
As always, I sought to bring about a change by peaceful means, by offering proposals to remedy this situation which meanwhile had become unbearable.
It is a lie when others in the world claim that we sought to carry out our revisions by the use of force exclusively. Fifteen years before National Socialism’s rise to power, there was ample opportunity to carry out these revisions by peaceful means. Nothing of the sort was done. In any event, I made proposals for a revision not once, but many times.
https://der-fuehrer.org/reden/english/39-09-01.htm