For at least the past two hundred years, ethnoconfessional nationalism has been the most powerful ideology and force shaping political and social developments in southeastern Europe. This dissertation argues that Balkan ethnoconfessional nationalism is such an important element in southeastern Europe because it is a collective, chronic and non-economic phenomenon which transcends other political ideologies, generations, or socio-economic classes. As such, conventional Marxist-based approaches to understanding the phenomenon of nationalism, and their intellectual descendants such as the more materially-based forms of social constructivism and instrumentalism, consistently fail to both understand and predict its appeal and success in southeastern Europe. The dissertation concludes by arguing that there are severe limitations to the extent to which outsiders can manage the outcome of ethnoconfessional conflicts; hence, in terms of policy prescriptions, the analysis provided in this dissertation argues for a cautious and modest understanding of the extent to which intervention by the international community can transform Balkans states and societies