The Ordnungspolizei, abbreviated Orpo, were the uniformed police force in Nazi Germany between 1936 and 1945.The Orpo organisation was absorbed into the Nazi monopoly on power after regional police jurisdiction was removed in favour of the central Nazi government (verreichlichung of the police). The Orpo was under the administration of the Interior Ministry, but led by members of the Schutzstaffel (SS) until the end of World War II. Owing to their green uniforms, Orpo were also referred to as Grüne Polizei (green police). The force was first established as a centralised organisation uniting the municipal, city, and rural uniformed police that had been organised on a state-by-state basis.
The Ordnungspolizei encompassed virtually all of Nazi Germany's law-enforcement and emergency response organisations, including fire brigades, coast guard, and civil defence. In the prewar period, Reichsführer-SS Heinrich Himmler and Kurt Daluege, chief of the Order Police, cooperated in transforming the police force of the Weimar Republic into militarised formations ready to serve the regime's aims of conquest and racial annihilation. Police troops were first formed into battalion-sized formations for the invasion of Poland, where they were deployed for security and policing purposes, also taking part in executions and mass deportations. During World War II, the force had the task of policing the civilian population of the conquered and colonised countries beginning in spring 1940. Orpo's activities escalated to genocide with the invasion of the Soviet Union, Operation Barbarossa. Twenty-three police battalions, formed into independent regiments or attached to Wehrmacht security divisions and Einsatzgruppen, perpetrated mass murder in the Holocaust and were responsible for widespread crimes against humanity and genocidetargeting the civilian population.