Since the end of the Cold War regions have been seen to assume more significance in international politics with regional powers and regional institutions regarded as playing important roles in regional and global order (Fawcett and Hurrell 1995; Mansfield and Milner 1999; Acharya and Johnston 2007). The decentralization of the international system has exposed new security patterns and interdependencies and increased the autonomy of regional actors. This, together with the overload on existing multilateral institutions, notably the United Nations, has led to an increased demand for, and supply of, regional action. However, these processes have been patchy in their global impact and the question of why some regions have outperformed others is particularly pertinent and interesting (Farrell et al. 2005).