Effective peacebuilding in the aftermath of civil war usually requires the deep reform of security institutions, a process frequently known as security sector reform. Nearly every major donor, as well as a growing number of international organizations, supports the reform of security organizations in countries emerging from conflict and suffering high levels of violence. But how are reform strategies implemented? This collection of nine case studies examines the strategies, methods, and practices of the policy makers and practitioners engaged in security sector reform, uncovering the profound conceptual and practical challenges encountered in transforming policy aspiration into practice. This book was previously published as a special issue of Civil Wars .