The attempt to explain cooperation on defence procurement among European states arises from the observation of real endeavours to harmonize and coordinate weapon systems acquisition and management procedures. The relevance of this topic is self-evident, as standardized and interoperable weapons are the preliminary condition for the creation of European defence might.¿Cooperation¿ is one of the subject-matters that mainstream International Relations schools of thought have problems dealing with powerfully and convincingly. Cooperation on security matters has posed even more challenges to the theoretical debate. Thus, the aim of this book is to investigate the shape and dynamics characterizing coordination efforts in a domain traditionally kept under National States' control.