After Hitler‘s appointment as Reich Chancellor, the German police was changed according to National Socialist ideology. As early as 22 February 1933, the Sturmabteilung (SA) was declared an auxiliary police force and thus the police were under the direct influence of the SA.
With the emergency decree of 28 February 1933, »Decree of the Reich President for the Protection of the People and the State« (also known as the Reichstag Fire Decree), police powers were extended. Basic rights were suspended. From now on, the police could »take all necessary measures (…) in direct norm-free application of state power«. House searches and arrests could be carried out arbitrarily. Mass arrests were made against the SPD and KPD, and trade union buildings and newspaper editorial offices were occupied.
After the NSDAP‘s rise to power and the enactment of the Law for the Restoration of the Professional Civil Service of 7 April 1933, all civil servants who did not agree with the National Socialist ideology were dismissed from their jobs without pension rights. The Frankfurt police were »brought into line«.
On 17 June 1936, the police were reorganised in the Reich Ministry of the Interior and placed under the control of Heinrich Himmler. Heinrich Himmler, Reichsführer Schutzstaffel (SS) and Chief of the German Police in the Reich Ministry of the Interior from now on held two Reich-central main offices: the Order Police and the Security Police, which consisted of the State Police Office and the Prussian State Criminal Police Office. The Schutzpolizei, Gendarmerie and Gemeindepolizei were gathered under the umbrella of the Ordnungspolizei under the leadership of Kurt Daluego, and the Sicherheitspolizei was composed of the Kriminalpolizei and the Secret State Police under the leadership of Reinhard Heydrich.
A reorganisation and centralisation of the entire German police force was implemented. The police authorities were brought together under a Reich-wide central authority and an independence from the courts and the public prosecutor‘s office took place. The police were gradually removed from the authority of the general state administration by establishing their own personnel administration and introducing disciplinary and criminal jurisdiction for the police.
With the decree of the Reich Ministry of the Interior on 14 December 1937 on »Preventive Crime Control by the Police«, the police could, in line with Nazi ideology, not only monitor all people classified as »alien to the community« but also immediately take them into custody or deport them to a concentration camp.
In 1939, the Security Police were merged with the Security Service (SD) to form the Reich Security Main Office. This merger made it almost impossible to distinguish between the activities of the Criminal Police and the Secret State Police (Gestapo). Both police departments investigated independently, only following the instructions of the police leadership and only submitting cases to the public prosecutor‘s office that had been released for disposal by the police leadership.
The alleged crime prevention was radicalised in the sense of National Socialism. Allegedly »criminal and socially harmful hereditary traits« were at the forefront of the persecution. To »prevent the transmission of a bad hereditary stream to the healthy body of the people« and the »eradication of pests of the people« were grounds for imprisonment, forced labour and murder from 1933 onwards.
With the establishment of a German police force authorised to issue directives, a comprehensive network for persecution was set up. To house prisoners, the police and the Gestapo had at their disposal, among others, the police prison in Klapperfeldstraße, the remand prison in Hammelsgasse and various emergency prisons.