Classic example of what happens when one group fails to assimilate into the main country, much like the illegals want to do to the USA. You can’t have two different cultures living in the same country and have harmony, it doesn’t work.
Silesia is a region that has been fought over by empires for a thousand years. There are sub-regions within the area that have historically been more in 1 empire’s orbit than the others. I’m talking about Germany, Austria-Hungary, Russia & Poland. (Sorry Poland, but your holding the bag on this one!)