For those who are interested in diving into Poland's history and role in starting WWII, this is an excellent deep dive: https://ww2truth.com/2021/07/01/the-unknown-history-of-the-1939-german-polish-conflict/

TL:DR

1. Poland and Germany had a centuries' long feud.
2. Prior to WWII, Poland was infiltrated by communists.
3. During/after the global Great Depression, Poland (as well as other countries) were desperate for financial aid. Poland also wanted Danzig.
4. Poland makes a back-door deal with Britain for protection and reparation in the case of war.
5. Despite Germany's efforts to ease tensions, Poland began massacring ethnic Germans living in Poland, to egg Germany into invasion, and, subsequently, bringing Britain into the conflict.