As a formal agency, the SiPo was incorporated into the Reich Security Main Office (RSHA) in 1939, but the term continued to be used informally until the end of World War II in Europe.

The term originated in August 1919 when the Reichswehr set up the Sicherheitswehr as a militarised police force to take action during times of riots or strikes.

[2] When the Nazis came to national power in 1933, Germany, as a federal state, had myriad local and centralized police agencies, which often were un-coordinated and had overlapping jurisdictions.

Heinrich Himmler and Reinhard Heydrich's plan was to fully absorb all the police and security apparatus into the structure of the Schutzstaffel (SS).

[11][12] The Einsatzgruppen had its origins in the ad hoc Einsatzkommando formed by Heydrich to secure government buildings and documents following the Anschluss in Austria in March 1938.

[16] When the units were re-formed prior to the invasion of the Soviet Union in 1941, the men of the Einsatzgruppen were recruited from the SD, Gestapo, Kripo, Orpo and Waffen-SS.