Abstract: During the Cold War, doubts over the credibility of the US commitment to defend Western Europe led Great Britain and France to develop their own nuclear capabilities, despite their inclusion under the US "nuclear umbrella". In other instances the US nuclear umbrella appears to have been much more credible. For example, Japan, Taiwan, and South Korea did not pursue nuclear weapons, in large part because of their alliances with the US. Why did the US commitment to defend Europe lack sufficient credibility, while its commitment to defend Asia seemed more effective? This paper develops one answer to this puzzle by exploring how the institutional design of nuclear umbrellas may affect its credibility. I posit that nuclear security commitments are more likely to be perceived as credible when they include costly reliability-enhancing provisions, such as greater precision in when alliance obligations apply, issue-linkages, and increased military institutionalization. In the empirical section of the paper, I demonstrate three observable implications of this logic that are consistent with a client state feeling more assured. I show that more precise and institutionalized alliances between a nuclear weapons state and non-nuclear client state are strongly associated with (i) lower defense spending in the client state, (ii) a lower likelihood that a client state will pursue its own nuclear weapon, and (iii) fewer alliance commitments held by the client state. These results have important implications for how policymakers and analysts evaluate the consequences of nuclear policy choices.

About the Speaker: Neil Narang is a Stanton Junior Faculty Fellow at the Center for International Security and Cooperation (CISAC) at Stanford University and an Assistant Professor in the Department of Political Science at the University of California, Santa Barbara. Previously, he served as the Director of the Public Policy and Nuclear Threats (PPNT) Program at the University of California Institute for Global Conflict and Cooperation (IGCC)and as a Nonproliferation Policy Fellow at the Los Alamos National Laboratory.