Germany introduced martial law in the region, which allowed for even more blatant persecution of Poles. In August and September 1939, the Germans carried out mass arrests of Poles, including activists, teachers, school principals, bank employees, newspaper editors, entrepreneurs, priests, scout leaders, and the consul and employees of the Polish Consulate in Olsztyn, and shut down or seized Polish newspapers and libraries. Arrested Poles were mostly deported to concentration camps, incl. , Soldau, Stutthof, Sachsenhausen, Gusen and Ravensbrück. During World War II, many Poles from the region were forcibly conscripted into the Wehrmacht. The Germans operated a notable Nazi prison in the town of Barczewo (Wartenburg) with several forced labour subcamps in the region. Polish Republic Following Germany's defeat in World War II, and the Yalta Conference and Potsdam Conference of 1945, Warmia became again part of Poland as part of the so-called Recovered Territories, pending a final peace conference with Germany which eventually never took place. The German inhabitants either fled or were transferred to Germany by Soviet and communist authorities installed in Poland and the remaining Polish inhabitants were joined by Polish settlers, many of whom were displaced from former eastern Poland annexed by the Soviet Union. Olsztyn is the largest city in Warmia and the capital of the Warmian-Masurian Voivedeship. During 1945–46, Warmia was part of the Okreg Mazurski (Masurian District). In 1946 a new voivodeship was created and named the Olsztyn Voivodeship, which encompassed both Warmia and Masurian counties. In 1975 this voivodeship was redistricted and survived in this form until the new redistricting and renaming in 1999 as Warmian-Masurian Voivodeship. The Catholic character of Warmia has been preserved in the architecture of its villages and towns, as well as in folk customs. The most precious historic heritage sites of Warmia are the Lidzbark Castle, the main seat of the Prince-Bishops of Warmia, and Frombork Cathedral, the bishopric's cathedral. Both objects are listed as Historic Monuments of Poland. Cities and towns Gallery People Nicolaus Copernicus (1473 in Toruń – 1543 in Frombork), mathematician and astronomer Stanislaus Hosius (1504 in Krakow – 1579 in Capranica), Polish writer and diplomat, Bishop of Warmia Marcin Kromer (1512 in Biecz – 1589 in Lidzbark Warmiński), Polish cartographer, diplomat and historian, personal secretary of Kings of Poland, Bishop of Warmia Regina Protmann (1552 in Braunsberg – 1613 in Braunsberg), Polish Roman Catholic, founder of the Sisters of Saint Catherine Andrzej Chryzostom