Bielsko-Biała language island
The Bielitz-Biała language island or Bielsk language island (German: Bielitz-Bialaer Sprachinsel, Polish: Bielsko-bialska wyspa językowa) was a Silesian language island within the Polish-speaking areas on the border of Austrian Silesia and Galicia. It existed from the 13th century to approximately 1943 within a region of thirteen towns, most of which fell within the boundaries of modern-day Bielsko-Biała in southern Poland.
Bielsko, which was originally its own city, had the largest German-speaking population in the Duchy of Teschen until after World War Two, when most Germans fled or were expelled by the Soviets under the Potsdam Conference. This deportation is often considered an act of forced Polonization.