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.[3] During World War II, the force had the task of policing the civilian population of the conquered and colonised countries beginning in spring 1940.[1] 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 genocide targeting the civilian population.