Based on a 3-year ethnography on crime prevention of the police in Germany, this article analyses how the police incorporate youth in their de-escalation work preceding an annual demonstration on the 1st of May. A multimodal conversation analysis of work meetings traces how membership categorisation and assumption of social responsibility change: over the course of several months the police turn initially reluctant youth who the police at the outset considered ‘troublemakers’ into their ‘helpers’. They build an alliance by working with youth centres, influential people from the neighbourhood and participants of the previous year’s project. Whereas the police are the driving force at the beginning of the project, on the day of the demonstration they remain in the background and merely supervise the youth. This sequential development is discussed as a precarious process of disciplining the youth, driving the formation of a neighbourhood community and encouraging political consensus in society.