Sicherheitspolizei
The Sicherheitspolizei (German: Security Police), abbreviated as SiPo, Sipo or SIPO, was a term used in Germany to describe the state political and criminal investigation security agencies. It was made up by the combined forces of the Gestapo (secret state police) and the Kripo (criminal police) between 1934 and 1939 and was headed by Supreme Commander Heinrich Himmler, but the term continued being used informally until the end of the Third Reich.
History
The Security Police were originally a paramilitary German police force established in most Weimar Republic states in late 1919 and largely financed by the German Reich. It was the first German barracked police force and the forerunner of today's riot police. They were ready for use nationwide in mid-1920.
In view of the unstable domestic political situation with civil war-like conditions, especially in the Reich capital Berlin, Captain Waldemar Pabst from the Guard Cavalry Rifle Corps considered a barracked and militarily armed and trained police force necessary. It should be a more useful tool in counterinsurgency than the existing police forces inherited from the monarchy. During the Berlin March Battles on 10 March 1919, Pabst sent a corresponding concept to the Reichswehr Minister Gustav Noske, who approved the plan and, together with Wolfgang Heine, promoted its implementation. According to Noske's wishes, the police force created in this way should also form the core of the new Reichswehr.
On 8 September 1919, 2,500 protection police (Schutzpolizei) officers from all over Germany demonstrated with the Reich Association of German Police against the establishment of the Sipo. In contrast to the traditional individual police, who usually wore blue uniforms, the Sipo was also called the “green police” after the color of its uniform. The gray-green uniform largely corresponded to the uniform of the army's Jäger troops. A special external feature was the shako (Tschako) as headgear, which was also adopted by the hunters.
At the end of 1920, the security police were disbanded due to French protests and, depending on the state, either the protection police (Schupo; in the Free State of Prussia, Saxony and Württemberg), the state police, such as the Bavarian State Police in the Free State of Bavaria, or the public order police (Orpo; in Hamburg, Oldenburg police in the Free State of Oldenburg, Lübeck, Anhalt, Baden, Mecklenburg-Schwerin). In Hesse the term security police was retained, in Mecklenburg-Strelitz the security police was renamed the state police, in Thuringia the term state police was used (from 1931 also protection police), and in the Republic of Baden the term group police.
National Socialism
The term was revived in the early years of NSDAP power in Germany. The German Reich, as a federal state, had a myriad of local and centralized police agencies, which often were un-coordinated and had overlapping jurisdictions. Himmler's plan was to fully absorb all the police and security apparatus into the structure of the SS. As a result, the 
took command first of the Gestapo (itself developed from the Prussian Secret Police or Preußische Geheimpolizei) and later of all the regular and criminal investigation police.
Eventually, the state security police were consolidated and placed under the central command of Reinhard Heydrich, already chief of the party Sicherheitsdienst (SD), and named Sicherheitspolizei. The idea was to fully identify the party agency (SD) with the state agency (Sipo). Most of the Sipo members were encouraged or volunteered to become members of the SS and many held a rank in both organisations. In practice, however, the Sipo and the SD frequently came into jurisdictional and operational conflict with each other, due in large part to the fact that the Gestapo and Kripo had many experienced, professional policemen and investigators, that considered the SD as an organisation of amateurs and often found the SD an incompetent agency.
In 1936, the state police agencies in Germany were statutorily divided into the Ordnungspolizei (regular or order police) and the Sicherheitspolizei (security police). The two police branches were commonly known as the Sipo (Kripo and Gestapo combined) and Orpo.
In 1939, with the founding of the Reichssicherheitshauptamt (RSHA), the Sicherheitspolizei as a functioning office ceased to exist. The term survived in common usage, however, and was most often used by local security force commanders who adopted the title Inspektor des Sicherheitspolizei und SD. Such personnel typically had command over all SD, Gestapo, Kripo, and Orpo units in their area of responsibility and performed duties befitting a modern day Chief of Police. The Inspectors of the Security Police answered to both the RSHA and to local SS and Police Leaders.
