Why did Hitler invade Poland?

(i) Germany wanted to regain lost territories which were given to Poland. Especially, the port of Danzig. Germany was divided into two parts to provide a land route to Poland. (ii) Danzig was mainly occupied by Germans and by occupying the Danzig corridor, Germany would have direct connections with East Prussia. (iii) Germany and Russia had signed a non-aggression pact in 1939 and it accused Poland of committing atrocities against Germans.