How do animals participate in police work? Drawing on an ethnographic study of a system of professional training for police dog teams, this article shows how the training of police patrol dogs socializes animals in the ways of police work. The bravery expected of these police dogs has its source in the working relationship of their police handlers, who are imbued with the security ideology of anti-delinquency policies. The training creates a police framework for canine aggressiveness in complementary disciplinary spaces: the ring provides reinforcement for aggression based on a mock struggle, the kennel exposes them to social isolation. Police handlers shape the behaviour of their canine companions to reflect the ideological and practical violence of their work.