When the Mongols invaded Eastern Europe in the 1240’s, they got as far as Liegnitz, Germany (now in Poland) and Hungary. But after their leader died, they had to go back to Mongolia to choose a new one.
Fast Forward to 1920. The Poles handed the Bolshevik horde a series of stunning defeats to establish modern Poland.
en.wikipedia.org/wiki/Battle_of_Warsaw_(1920)
The modern boundaries of Poland are however, pretty much those agreed upon by Hitler and Stalin in 1939, with some post-war jiggery-pokery.
There are small regions in Poland where ethnic Germans,Russian, Ukrainians, etc. are still dominant. However, with perhaps the exception of the Germans, they have one hell of a better deal than they would have among their ethnic countrymen.