Of course at the time in was part of Germany. That East Prussian “attraction” in present day Poland would be less controversial if they named it after Count von Stauffenberg and it would be appropriate as it is the site where his brief case bomb exploded but failed to kill Hitler on July 20th, 1944.
Also regarding hitler invading the USSR — that was his aim since the 1920s - he wrote what he was going to do in the Mein Kampf and he followed it to the letter.
People SHOULD read the MK - it is the writings of a mad-man. No one can read it and remain pro- or even mildly favourable to the Nutzis