In light of the continued insecurity, aggravated poverty and a decline in human conditions in many parts of Africa caused by conflicts, the African Union mainstreamed the promotion of peace, security and stability into its objectives. As a result, member States of the African Union adopted the Common African Defence and Security Policy as a blue print or conceptual framework in the search for peace, security and stability in Africa. This book elucidates the scope, principles and objectives of the Common African Defence and Security Policy, examines the norms and institutions relevant for its effective implementation and the existing mechanisms and critically analyzes the weaknesses, challenges and constraints faced by the different AU organs in implementing the Policy. The book employs the Somali crisis to examine the practical challenges the AU faced in implementing the Policy.