In the post-Cold War era, the Balkans came to exemplify the power of resurgent nationalisms freed from the straitjacket of bipolar stability. The break-up of the Yugoslav federation suggested that exclusivist ethno-national identities trumped the logic of political and economic integration. Yet, by the early 2000s, regional cooperation made significant inroads into South East Europe. This study addresses the puzzle of why the Balkan states have engaged in a number of multilateral schemes in fields such as military security, trade, infrastructure development, energy, despite the region's divisive historical legacies and political instability. The thesis explores the impact of three factors: regional interdependence denoting the socio-economic and political linkages which contribute to the convergence of Balkan states' material interests, external push referring to the policies for fostering regional cooperation adopted by key actors such as the EU, US, and NATO, and identity politics: the discourses on the borders, cultural make-up and history of a Balkan regional entity as well as the latter's relationship with constructs like Europe and the West. The thesis argues that external projection of power, rather than regional interdependence, accounted for the development and growth of Balkan regionalism. However, the push from outside was legitimised by Balkan collective identity built upon myths of belonging to and exclusion from 'civilised Europe'. Regionalism was not solely a reflection of the supply and demand for integrative frameworks, but amounted to a symbolic strategy for transforming the volatile Balkans into South East Europe by the adoption of the institutional norms and practices of international clubs such as the EU and NATO. The case of regional cooperation in South East Europe contributes to the debates about the politics of interest and the politics of identity in the field of International Relations, and raises questions about the nature of power in contemporary Europe and the international society.