This book outlines the role Regional Economic Communities in Africa can have for regional stability, security and development. Beginning with the development of a analytical heuristics based upon the Regional Security Complex Theory by Buzan and Wæver as well as Karl W. Deutsch's concept of Security Communities, this book then analyzes the cases of the South African Development Community (SADC), the Intergovernmental Authority on Development (IGAD) and the Economic Community of West African States (ECOWAS). Especially the role of Regional Powers for their Regional Economic Community will be emphasized and illustrated by considering recent regional conflicts. As this book will show, it is this interplay of Regional Powers and Regional Organizations that determines the regional security architecture.