I'm Polish and while Poland was gaining and losing land throughout history, it never involved killing, moving or polonising its inhabitants. conquered Ukrainians, Lithuanians, or whoever, were never forced to move to make room for Polish people, they were never put on reservations, their languages or cultures weren't suppressed. and they were never made minorities in their own regions - look up historic demographic maps of Poland, it's pretty interesting compared to modern Polish monoethnic state.

this contrasts with what happened in America. colonists didn't want to conquer natives and rule over them, they wanted to clear them out and make room for themselves.