This is the first book focusing on the effect of biased and neutral mediators in civil wars. The argument is tested through analysis of both global data and case studies of contemporary peace processes, and makes two main contributions. First, it explores the role of biased mediatorsin contemporary peace processes. The author develops a theory explaining why biased mediators are more effective than their neutral counterparts. Bias is here defined in terms of previous active support for one side in a civil conflict, either the government or the rebels. Systematising and developing ideas found in previous meditation studies, the book identifies four different causal mechanisms through which biased mediators can be effective peace-brokers. By developing a comprehensive set of mechanisms to explain bias mediation, the book helps deepen understanding of biased mediators in general, and their role in resolving civil conflict in particular. The second contribution offered is a novel way of measuring mediation success, a concept which has been much debated within the mediation literature. Previous research has concentrated on settlement, behavior, or implementation. These conceptualizations of mediation success all have merit, but also some basic flaws in that they do not pay sufficient attention to how the basic incompatible positions are regulated. This book focuses on mediators' ability to regulate core compatibilities by crafting institutional peace arrangements here termed 'peace institutions' that generally are considered to enhance the prospect for durable peace. This approach has a wider implication for peace and conflict research in that it brings together research on durability of peace and studies on international mediation, two fields of research which hitherto have been kept apart. This book will be of much interest to students of international mediation, conflict management, civil wars, security studies and IR in general.