This monograph addresses the challenging topic of transition in post-conflict stability operations and is intended for a wide audience that includes military and civilian policymakers, international development experts, and scholars in academe. It is a primer, systematic review, and comprehensive assessment of the fields of research and practice. It presents and appraises the major lenses (process, authority transfer, phasing, and end state), categories (war-to-peace, power, societal, political-democratic, security, and economic), approaches, and tools under which post-conflict transitions are conceived. It lays the groundwork for both future research and greater collaboration among diverse international and local actors who operate in post-conflict environments, to develop a comprehensive definition of transition and adequate tools to address all facets of the concept. It provides recommendations for future research and improved transition policy, which include: cross-institutional (political, security, economic) and multi-level (local, regional, national) studies that explore the interdependencies between simultaneous transitions ; underlying assumptions of current transition tools and indicators ; relationships between transition and institutional resilience ; and, thresholds and tipping points between transition phases.