Chapter 3 presents localized peace enforcement theory. It first discusses the challenges facing individuals involved in a communal dispute. Reflecting on these obstacles to peaceful dispute resolution, the chapter outlines a formal micro-level theory of dispute escalation between two individuals from different social groups who live in the same community. It explains how international intervention shapes escalation dynamics. The chapter then shifts the focus to local perceptions of intervener impartiality, which the theory posits are a key determinant of whether a UN intervention succeeds in preventing the onset of violence. The identifies the importance of multilateralism, diversity, and the nonuse of force as critical factors shaping local perceptions and, as a result, UN peacekeeping effectiveness. Critically, the theory does not suggest that UN peacekeepers will always succeed, or that all kinds of UN peacekeepers will succeed. Indeed, perceptions of UN peacekeepers vary depending on the troop-contributing country and the identity of the civilians involved in the dispute. The chapter closes with a discussion of the most important hypotheses derived from the theory.