What best practices can we learn from the successes and failures of peace operations? This book proposes a new framework to understand the components of peace missions in intra-state wars, in a failed-state setting. An original classification of peace operation outcomes explains the process of intervention according to the type of strategy and the type of intervener combined. This theoretical model is supported by a comprehensive comparison of 11 peace missions in Somalia, Liberia and Sierra Leone. Each case study features field research based on interviews with rebel leaders, military commanders and refugees.