When the Nazis came to power in January 1933, many policemen remained skeptical of the party and its intentions. Nazi agitation, especially in the latter years of the Weimar Republic, had been subversive and the police had been investigating both the Nazis and the Communists with vigor. Nevertheless Hitler posed as a champion of law and order, claiming he would uphold traditional German values. The police and many other conservatives looked forward to the extension of police power promised by a strong centralized state, welcomed the end of factional politics, and agreed to end democracy.
The Nazi state in fact alleviated many of the frustrations the police experienced in the Weimar Republic. The Nazis shielded the police from public criticism by censoring the press. They ended street fighting by eliminating the Communist threat. Police manpower was even extended by the incorporation of Nazi paramilitary organizations as auxiliary policemen. The Nazis centralized and fully funded the police to better combat criminal gangs and promote state security. The Nazi state increased staff and training, and modernized police equipment. The Nazis offered the police the broadest latitude in arrests, incarceration, and the treatment of prisoners. The police moved to take "preventive action," that is, to make arrests without the evidence required for a conviction in court and indeed without court supervision at all.
Conservative policemen were initially satisfied with the results of their cooperation with the Nazi state. Crime did indeed go down and the operation of criminal gangs ended. Order was restored. But there was a price. The Nazi state was not a restoration of the imperial tradition. It was at its core thoroughly racist. The Nazis took control and transformed the traditional police forces of the Weimar Republic into an instrument of state repression and, eventually, of genocide.
The Nazi state fused the police with the SS and Security Service (Sicherheitsdienst; SD), two of the most radical and ideologically committed Nazi organizations. Heinrich Himmler, head of the SS, also became the chief of all German police forces. His associate, Reinhard Heydrich of the SD, became at the same time the head of the Security Police, charged with safeguarding the Nazi regime. Nazi ideology became part of all police activities. The police were central figures not just in maintaining public order, but in combating the so-called racial enemies designated by the Nazi state. It was in this context that "preventive police action" took on such terrible consequences. The SS, SD, and police were the primary perpetrators of the Holocaust.