Extended Deterrence in the Nuclear Era: Strategy, Theory, and Consequences

Abstract

How do states practice extended deterrence? This dissertation examines how major powers make commitments to deter and defeat aggression against their junior allies, the conditions under which major powers use which practice, and the relative effectiveness of each framework in achieving the major powers’ strategic goals. With this dissertation, I make three core contributions to the fields of international relations and security studies. First, drawing on the signaling and deterrence literatures, I develop a novel typology of the strategies that major countries, such as the Soviet Union, the United Kingdom, and the United States, use to signal their commitments to deter and defeat attacks on their allies. By identifying how these countries use treaties, troops, and nukes to signal extended deterrence commitments, the typology brings coherence to our understanding of extended deterrence practices and shows how they systematically vary across both time and space.Second, I develop a theory identifying the conditions under which major powers will select a given strategy in the typology. I argue that the presence of a given strategy is largely driven by a strategic-choice process driven by the major power. The major power selects the strategy it believes will most satisfy its security goals, conditional upon the external and internal constraints it confronts. I identify system-, state, and alliance-level variables which, together, explain the outcomes of this strategic choice process and the major power’s selection of extended deterrence framework. I then test my theory using both a pattern-matching exercise against the universe of cases and a series of intensive case studies. Drawing on multilingual archival and secondary sources, I demonstrate how my theory outperforms prominent alternative explanations in the international relations literature. Third, using statistical methods, I evaluate the relative success of each framework in achieving various – and, at times, conflicting – strategic goals of the major power, such as deterring the adversary, reassuring the junior ally, and restraining the junior ally. The results indicate that major powers face tradeoffs in pursuing their extended deterrence goals and that simultaneously accomplishing multiple strategic goals will require the selection of more costly extended deterrence frameworks.