Book excerpt: 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. The involvement of international organizations in the realm of regional peace and security, and their cooperation in this domain with the United Nations, has reached an unprecedented level. 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. Despite suffering from important discrepancies in both their mandates and capacities, regional organizations have become indisputable actors that play a role from the outbreak of a crisis to the reconstruction efforts in the aftermath of a conflict Presenting the most up-to-date critical and comparative analysis of the major regional security institutions, assessing a wide range of regional organizations and providing an accessible and comprehensive guide to 11 key organizations, this book is the first systematic study of the capacities of the most recognized intergovernmental organizations with a security mandate. Regional Security is essential reading for all students of international organizations, peace and security studies and global governance.