After the end of the Second World War in 1945 , Oppeln was transferred from Germany to Poland according to the Potsdam Conference , and given its original Slavic name of Opole . Opole became part of the Katowice Voivodeship from 1946 – 1950 , after which it became part of the Opole Voivodeship . Unlike other parts of the so-called Recovered Territories , Opole and the surrounding region 's indigenous population remained and was not forcibly expelled as elsewhere . Over 1 million Silesians who considered themselves Poles or were treated as such by the authorities due to their language and customs were allowed to stay after they were verified as Poles in a special verification process . It involved declaring Polish nationality and an oath of allegiance to the Polish nation
Potsdam Conference
Potsdam Conference
Opole