During the German invasion of Poland, which started World War II, the "Einsatzgruppe I" entered Bielsko-Biała in the first half of September 1939 to torture, plunder, and murder Jews. During the war Bielsko-Biała was annexed and occupied by Nazi Germany. In 1939 Germans arrested several Polish teachers and principals who were then deported to Nazi concentration camps and murdered there. A prison for Poles was operated by the Germans in Bielsko-Biała. Many of its Jewish residents were murdered at the nearby Auschwitz extermination camp. Less than 1000 of Bielsko-Biala's Jewish community of nearly 8000 survived the war. After the defeat of Nazi Germany in 1945, the remaining German population fled westward or were expelled. The town was polonized and gradually repopulated by Polish settlers.