This volume brings together expert case studies on a range of experiences of third-party interventions in civil wars. The chapters consider the role of a variety of organisations, including the United Nations, NATO, the European Union, the Shanghai Cooperation Organisation, the Organisation of the Islamic Conference, the African Union, and the Organization of American States. Each case study features a presentation and analysis of empirical data in two dimensions: the organisation’s general capabilities to carry out intervention in civil wars and, specific to one particular intervention, the conflict context in which it happened. This serves two purposes. First, to offer insights into the dynamics of each individual case and helping us understand the specific outcome of an intervention effort, i.e., why did a mission (partially) succeed or fail. Second, it enables us to make real comparisons between the cases and draw policy-relevant conclusions about the conditions under which military, civilian and hybrid intervention missions are likely to succeed.This book was originally published as a special issue of Civil Wars.