The chapter starts with a theoretical discussion of the three main concepts, focusing on their common ground and mutual relations. It examines how military professionals in Bosnia and Herzegovina (BiH) understand, conduct and learn about regional cooperation. The main goal of this part is to comprehend the motivations which drive practitioners when they cooperate at the regional level and to determine when the practice of cooperation can contribute to security community-building. The chapter focuses on identifying practices which are performed because of practitioners' background knowledge, differentiating them from practices created and conducted by practitioners themselves. It argues that regional military professionals, in practising daily cooperation, create a community of practice which consequently helps to foster a regional security community and it describes some of the military professional dimensions. Finally, the chapter compares these practices with Deutsch's 'three tiers' of security community, to situate the Western Balkan security community within the theoretical framework.