After 1945, almost all of Upper Silesia (that was not ceded to Poland in 1922) was placed under the administration of the Republic of Poland. German civilians, as well as Nazi criminals, were interned in labor camps, like the infamous Zgoda labour camp [whose memorial we visit, see my forthcoming article on shoah.blog], the majority of the German-speaking population that had not fled were expelled, in accordance with the decision of the victorious Allied powers at their 1945 meeting at Potsdam.

The expulsions of German-speakers did not totally eliminate the presence of a population that considered itself German. In contrast to the situation in Lower Silesia, where almost the totality of the pre-war population that was expelled was exclusively German-speaking (only about 50-60% of the population of Upper Silesia was displaced to Germany, while over 95-97% of population of Lower Silesia was displaced), the pre-war population of Upper Silesia was in considerable number Roman Catholic mixed bilingual that spoke both German and Polish dialects, and their Polish linguistic skills were considered solid enough for them to be kept in the area.

I would recomend the eBook by Kunce, Aleksandra : Being at Home in a Place: The Philosophy of Localness, pp. 41–112 [23] After the war, Poles displaced from Polish territories incorporated into the USSR settled in Upper Silesia, but also Polish settlers from other overpopulated parts of Poland. Then, in the years 1945-1989, a large number of Poles from various parts of Poland settled in Upper Silesia, who received work, e.g. in the mines.

By November 14, 1990 the area formally became part of the Republic of Poland by virtue of the German-Polish border treaty and German Silesians remaining in Upper Silesia were formally recognised as part of the German minority in Poland.