The principle concentration camp for the Berlin area, Sachsenhausen was established in July 1936 near the town of Oranienburg (where the early concentration camp Oranienburg had been closed in 1934). In the early days of its operation, Sachsenhausen prisoners were primarily political opponents of the Nazi regime, although other groups were detained there as well, including Jews, Roma and Sinti, homosexuals, Jehova’s Witnesses, and so-called “asocials.” During the Kristallnacht pogroms of November 1938, the SS arrested some 30,000 Jews and held them in concentration camps at Sachsenhausen (c. 6,000), Dachau and Buchenwald.