After the German invasion of Poland in 1939, following Nazi racial policy, the Jewish population of Silesia was subjected to Nazi genocide with executions performed by Einsatzgruppe z. B.V. led by Udo von Woyrsch and Einsatzgruppe I led by Bruno Streckenbach, imprisonment in ghettos and ethnic cleansing to the General Government. In their efforts to exterminate the Jews through murder and ethnic cleansing Nazi established in Silesia province the Auschwitz and Gross-Rosen camps. Expulsions were carried out openly and reported in the local press. Those sent to ghettos would from 1942 be expelled to concentration and work camps. Between 5 May and 17 June, 20,000 Silesian Jews were sent to Birkenau to gas chambers and during August 1942, 10,000 to 13,000 Silesian Jews were murdered by gassing at Auschwitz. Most Jews in Silesia were exterminated by the Nazis. After the war Silesia became a major centre for repatriation of the Jewish population in Poland which survived Nazi German extermination and in autumn 1945, 15,000 Jews were in Lower Silesia, mostly Polish Jews returned from territories now belonging to Soviet Union, rising in 1946 to seventy thousand as Jewish survivors from other regions in Poland were relocated.