To you it may sem ridiculous, your country (Germany as it is) is around 300 years old.. you’ll never understand us :)
The inhabitants you mention were slaves, peasants we call them today. TK’s brutality in forcing their law is world reknown, peasants under their rule prefered to obey Polish King who at least ordered them to pay smaller taxes.
It’s not even that old. There was a “revolution” in 1848 without that much of an effect. The real birth of the German nation happened after the quick and superglorious (and justified - payback for Napoleon) concerted blitzlike preemtive attack of the German States against the French in 1870/71. Of course a loose “we are family” feeling existed for centuries before that.
We aren’t celebrating this today. Actually it would be worth to celebrate but then the French would feel offended.