The Wanderkessel is a police strategy to contain potentially violent demonstrators . A dense ring of police officers surrounds the demonstration and makes it impossible for the participants to leave the train. The traveling kettle was introduced in Berlin under the Interior Senator Wilhelm A. Kewenig (1981–1989) and has been used frequently since then.
The Wanderkessel is often criticized because it has an aggressive effect on peaceful demonstrators and can only provoke violence. Like any police cauldron , it makes it impossible for peaceful demonstrators to escape when violence breaks out.
In order to avoid traveling boilers, a form of demonstration called Out of Control is occasionally used.