pigpen

Tactic used by police, in which protests are smashed by police coercing protesters into a small space and then keeping them there by surrounding them and attacking anyone who tries to break out or asks to leave. Normally combined with verbal abuse and periodic baton charges against the protesters. It is basically a form of inhumane and extrajudicial imprisonment. Those held in pigpens often include not only protesters of all descriptions (and not only the ones cops claim to be targeting), and also anyone else who's on the scene, e.g. tourists, journalists, shoppers, local residents. The tactic has been used fairly regularly by British police against anti-capitalist protesters at events such as Mayday, Disarm DSEi and also at animal rights protests (all of which rely on small numbers of mobile people in small groups to cause disruption). Referred to as "corralling" in pig-speak; pigpen is the usual term used by protesters. I've also heard it referred to as a kettle, because it's identical to the tactic by this name which was used by the Russian army in Stalingrad.