How does the alliance between a client state and its nuclear ally influence support for proliferation in the client? Conventional wisdom suggests that when nuclear security guarantees are not credible, support for proliferation will be high, since a domestic nuclear capability offers an alternative source of deterrence. I introduce a new theory, which posits that highly credible security guarantees can backfire by causing some individuals to fear their ally might miscalculate—either by using nuclear weapons in an unnecessary preventative attack or by precipitous escalation of a crisis or conflict. Survey experiments conducted among representative samples of South Korean citizens in 2018 and 2019 support this theory, showing that increases in the credibility of the US nuclear security guarantee lead to increased support for nuclear proliferation among South Korean respondents.

This paper utilizes survey experiments among representative samples of U.S. and South Korean citizens to investigate the strength of the nuclear taboo in both countries. It finds evidence that a majority of respondents in both countries prefer to respond to conventional military invasions with options that do not involve a nuclear first strike. Furthermore, the paper addresses the question: Can states alter support for nuclear use by credibly signaling their intent to avoid or limit nuclear escalation? The evidence suggests that they can. As the probability of nuclear retaliation increases, support for nuclear use decreases. Public Significance StatementThis project helps explain when and why individuals are most likely to support the use of nuclear weapons. It shows the conditions under which nuclear use gains approval as well as public preferences about nuclear targeting.

A number of proposals for reducing tensions with North Korea have discussed alterations to the program of joint military exercises (JMEs) that South Korea holds. North Korea has also repeatedly called for a reduction or secession of JMEs. Would limiting or halting JMEs be a useful concession for securing a reduction of tensions on the peninsula? We argue that JMEs do not deter North Korea but, instead, provoke provocative rhetoric and actions, demonstrating that North Korea views JMEs as a serious threat to its security. In this paper, we establish a relationship between JMEs and North Korea’s actions. In response to a JME, North Korea can issue warnings or threats as well as take costly signals such as conducting missile or nuclear tests. Using new data on JMEs and North Korean behavior, we find that North Korea systematically responds with aggression to South Korean JMEs. Moreover, we find that the intensity of North Korea’s responses to JMEs is driven by the severity of the threat particular exercises pose, indicating that North Korea responds to JMEs as serious security threats.

This paper investigates the escalation dynamics of cyber attacks. Two main theories have been advanced. First, “means-based” theory argues attack type determines response; cyber attacks are less likely to escalate than kinetic attacks. Second, “effects-based” theory argues an attack’s material consequences determine the likelihood of retaliation. We advance a third perspective, arguing that the covertness of an attack has the largest effect on its propensity towards escalation. We identify two characteristics of covertness that affect support for retaliation: the certainty of attribution and its timing. We use a survey experiment to assess public support for retaliation, while varying the means, effects, timing, and attribution certainty of attacks. We find no evidence for the effects-based approach, instead finding high levels of support for retaliation regardless of an attack’s scale. We find that the most significant contributor to support for retaliation is an attack’s covertness.

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