sentences:  From 1816–1945 Opole was the capital of Regierungsbezirk Oppeln within Prussia.The city became part of the German Empire during the unification of Germany in 1871.After the defeat of Imperial Germany in World War I, a plebiscite was held on 20 March 1921 in Oppeln to determine if the city would be in the Weimar Republic or become part of the Second Polish Republic.