German policing was complex under Nazi rule, with Heinrich Himmler overseeing various groups including the Gestapo secret police and SS paramilitary force. The SS grew enormously during World War II and had influence in many aspects of German life, including policing, concentration camps, and racial policies. Though smaller than the SS, the Gestapo maintained control through fear and relied heavily on public denunciations to carry out arrests. Historians debate the extent to which terror from the SS and Gestapo was necessary for Nazi control of Germany or whether their powers were exaggerated.