Wow, quite a sweeping view of historic Poland, with insights into the histories/motives of neighboring countries (its like, a really good version of those reports we had to do in 6th grade...mine was Costa Rica). I have attempted similar sweeping views of a) The Caucasus and b) Northwestern Europe as follows:

https://medium.com/p/c4814cea69df

https://medium.com/p/1c2740d2ef54

(Note: Are your "West" and "East" Poland where ancient "Bell-Beakers" met the "Corded Ware Culture"?)

In my limited knowledge of Poland:

1) My father was imprisoned in Stalag Luft III in Zagan. We visited in 2019. The road from Berlin deteriorates badly just across the border. I know that many Polish expats flew in the Battle of Britain, and a strong Anglo-Polish alliance exists to this day.

2) I've been to Estonia and elsewhere in Europe. It would seem the Baltic States, parts of Poland and Ukraine have a heavy Nordic influence, perhaps going back to Viking "Kievan Rus" of the 8th-12th Centuries. It would also seem that these people have always resented the influence of Germans to the West, and Russians to the East (who in the 8th-12th Centuries were more primitive people).

3) Baltic expats I've met, who experienced WW II, all said they hated both Hitler and Stalin, but that Germans were the lesser of the evils (but they were not Jewish...since Hitler killed 6 million and Stalin 1.5 million, I guess that's complicated).

4) Goes to show there's a lot of different things going on in Poland, I'm sure we'll be learning more since they are such an important hedge against Russian expansion.