This study focuses on the escalation of collective violence in ongoing intra-state conflicts, which means that it is not an analysis of conflict onset, but rather a study of conflict duration. The results of the author's intensive field research into and case analysis of the Sri Lankan Civil War, instigated by the Tamil Tigers during the 1980s, demonstrate that both the causal mechanisms bound to the local and international legitimacy of the conflict and the political opportunities that arose directly from it can be used to explain the sudden escalation of political violence during the war. The new hypotheses generated during the study answer the following research question: How can we deal with the logic of violence between war and peace, which either leads the warring factions to a state of stable peace or to a further escalation of violence?