This course analyzes the link between identity and action in episodes of collective violence, underscoring the endogeneity of identity to violence and the resulting interplay between local and the supra-local affinities. Topics include the following: identity based explanations for violence; measuring identity; identity complexity and salience; measuring violence; group membership and the fragility of group solidarity; the ritualization of violence; violence and collective memory; case studies - the blood feud, ethnic violence, civil war and genocide.