This thesis examines the roles and significance of ECOWAS (Economic Community of West Africa States) in conflict prevention, crisis response and security-building processes in West Africa, particularly since 2000. The importance of developing regional institutions and capacities for peace and security-building in Sub-Saharan Africa has been widely recognised since at least the mid-1990s. Not only has the African Union developed important peace and security building aims and roles, but so too have several of the sub-regional organisations in Africa, including ECOWAS in West Africa. In the late 1990s, ECOWAS Member States achieved a number of noteworthy sub-regional agreements on ECOWAS norms and mechanisms for conflict prevention, crisis response, and peace and security –building in West Africa. These agreements and mechanisms have subsequently been further developed since 2000, in a dynamic process that was informed by experience with efforts to respond to a range of crises and conflicts in the region. This thesis critically examines this process, focussing particularly on the extent to which, and how, ECOWAS norms, institutions and mechanism have continued not only to develop but also to be influential in practice. Our research demonstrates that the ECOWAS agreements and norms established by 2000 have continued subsequently to be dynamically developed and used by ECOWAS member states and West African networks, in close interaction with several international partners. It argues that these norms and mechanisms have played significant roles in influencing actual policies, practices and missions. They have therefore proved to be more than shallow symbolic or paper agreements, despite the political fragility and divisions of the region and most of its states. We argue that this cannot be adequately understood using single explanatory frameworks, such as Nigeria’s hegemonic influence or instrumental influence of external Actors such as UN, EU or USA, as has often been suggested. Adequate explanations need to combine these factors with others, including relatively consistent investment in regional norms and institutions by coalitions of some West African states (including Ghana, Senegal and Nigeria) together with civil society and parliamentary networks. Our research then examines in detail the extent to which, and how, ECOWAS norms and mechanisms on conflict prevention, crisis response and security sector reform were significant and influential in ECOWAS’ responses to the crises and conflicts in Cote D’Ivoire, Mali and to a lesser extent in Gambia since 2003; and also how these crises were in turn influential in the further development of ECOWAS norms in these areas. We demonstrate numerous weaknesses in the implementation and effectiveness in these norms; and limitations in their diffusion and influence. However, we argue that such weaknesses and limitations are typical of regional peace and security norms everywhere, including much more stable and developed regions. Equally significant is that substantial coalitions exist between ECOWAS member states and stakeholders. Despite obvious tensions, ECOWAS, AU, UN and other countries such as France continue to work to address inherent tensions and develop mutually beneficial collaborations that enhance effective conflict prevention in the sub-region. The study draws on the knowledge created within this this thesis to propose a framework for conflict intervention. / Allan & Nesta Foundation