[Brian Griffin]

There is the matter of much of what is now Western Poland that used to be much of eastern Germany.

Poland might not wish to get its pre-WW2 borders back.

I should add that in the 17th century, Poland used to extend far to the east.

[Cronos]

In the 17th century “Poland” didn’t extend far to the east, the “Polish Lithuanian Commonwealth” did.

It was a multi ethnic, multi cultural country with Poles, Lithuanians, Ruthenians, Livonians, Jews etc.