This research identifies and characterizes a U.S.-centric counter nuclear smuggling network in Europe, and recommends ways to improve its cooperation and effectiveness. The purpose is to provide USSOCOM, NSHQ, and the larger counter proliferation CP community with an understanding of how the current network functions, its strengths and weaknesses, and how it can be improved. The research starts by examining prominent theories of international relations to understand cooperation within the network. Afterward, social network analysis SNA is used to define the Counter Nuclear SmugglingEurope CNS-E network and characterize its structure. Lastly, the function of the network is assessed using realistic vignettes based upon current threats in Europe. The results of this research indicate that the CNS-E network is highly decentralized and dense. Cooperation is abundant, though not sufficiently strong to ensure that information is shared. This research concludes by making the following recommendations 1 The U.S. government should focus on strengthening existing relations, not creating new relations 2 The network should centralize capabilities and information in regional hubs 3 USSOCOM and NSHQ should establish strong relationships with law enforcement agencies 4 USSOCOM and NSHQ can contribute to nonproliferation efforts by conducting threat assessments of European chemical biological radiological nuclear CBRN facilities.