Regional organizations are an inescapable feature of global politics. Virtually, all countries in the world are members of at least one regional or other intergovernmental organization. Regional organizations have traditionally been formed around economic, political, or environmental objectives. However, over the last decades these organizations have gradually penetrated into the security sphere and developed their capacities in conflict prevention, peacekeeping, or post-war reconstruction. In Europe, Africa, Asia, or the Americas, regional and other intergovernmental organizations have been concurrently empowered by the UN and their own member states to maintain peace and security. This book is the first systematic study of the capacities of the most recognized intergovernmental organizations with a security mandate. The author examines organizational capacity (legal mandate and organic structure), resource capacity (financial and human assets), and operational experience (ground record) of each organization. It provides the most up-to-date comparative analysis of the major regional security institutions.