From the thesis abstract: "This essay explores the connection between security guarantees and nuclear proliferation by allies of great powers. I propose a model to explain why U.S. allies pursue nuclear proliferation. I assert that this movement toward nuclear weapons occurs when an ally perceives that the U.S. defense commitment has become insufficient for the threat environment. I test this model using a case study of South Korea's exploration of nuclear weapons in the 1970s. South Korea was facing a severe threat environment when US President Richard Nixon announced that US allies would need to take greater responsibility for their own security. In response, South Korea began to explore a nuclear weapons program. In this context, South Korea's leaders interpreted the United States' attempt at alliance burden-shifting as a sign of abandonment. This perception tilted the threat-commitment balance out of alignment and led to forward movement toward nuclear proliferation. From this case and model, I conclude that US allies take steps advancing nuclear weapons activity when their perception of their threat environment outweighs their perception of US security commitment. From this conclusion, I draw implications about the role of presidential rhetoric and military force posture in assure US allies and discouraging nuclear proliferation."
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