Culminating in the creation in 2004 of the European Defence Agency (EDA), the post-Cold War development of European armaments organizations has impressed social scientists and policymakers alike as a momentous development. However, their theoretical diversity, prior analyses of armaments organizations err in their focus on recent organizations of a European character. The narrow focus on institutions tied to the EU has led scholars to neglect the long-term and incremental dynamics driving the development of armaments organizations on both a transatlantic and European basis. In fact, European states' participation in international armaments organizations is neither a recent phenomenon nor one that has historically been distinctly rooted in broader processes of European integration. By examining the development of European and transatlantic armaments organizations prior to the EDA, this article sheds new light on how this domain of international organization emerged and is likely to develop. Abstracting from the prior evolution of armaments organizations, this field is likely to continue to evolve along polycentric lines, with intergovernmentalism, rather than 'Europeanization' and 'Brusselization' remaining the motive forces for future change.