Credible Nuclear Security Commitments Can Backfire: Explaining Domestic Support for Nuclear Weapons Acquisition in South Korea

• Date: 01 July 2020
• Author: Lauren Sukin
• DOI: 10.1177/0022002719888689
• Published date: 01 July 2020
• Subject Matter: Articles

Article

Credible Nuclear

Security Commitments

Can Backfire: Explaining

Domestic Support

for Nuclear Weapons

Acquisition in South Korea

Lauren Sukin

1

Abstract

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.

Keywords

nuclear weapons, nuclear proliferation, public opinion, security guarantees,

credibility

1

Department of Political Science, Stanford University, CA, USA

Corresponding Author:

Lauren Sukin, Department of Political Science, Stanford University, 616 Serra St. #100, Stanford, CA

94305, USA.

Email: lsukin@stanford.edu

Journal of Conflict Resolution

2020, Vol. 64(6) 1011-1042

ªThe Author(s) 2019

Article reuse guidelines:

sagepub.com/journals-permissions

DOI: 10.1177/0022002719888689

journals.sagepub.com/home/jcr

How does the alliance between a client state and its nuclear ally influence support for

proliferation in the client state? The literature on this question primarily looks at one

mechanism through which nuclear allies have often tried to reassure client states

about their security—nuclear security guarantees. These guarantees suggest that the

nuclear ally is willing and prepared to use nuclear weapons to come to the client

state’s aid if it faces a sufficient security threat.

A crucial characteristic of these guarantees is their credibility or the degree to

which it is believed that the nuclear ally will actually follow through on its promises.

The conventional wisdom posits that credible nuclear security guarantees can sub-

stitute for proliferation by resolving a client state’s security concerns (Bleek and

Lorber 2014; 2009; Jo and Gartzke 2007; Monteiro and Debs 2014; Sagan 1997;

Singh and Way 2004). The logic runs as follows: if the client state can count on its

nuclear ally for defense, it should no longer have a need for nuclear weapons of its

own. As a result, there should be low support for nuclear weapons acquisition when a

client state has a nuclear security guarantee with high credibility and high support for

nuclear weapons acquisition when there is no nuclear security guarantee or when

there is a low-credibility guarantee.

This article introduces an alternative framework, which I call the “unwanted use

theory.” Unwanted use theory explains that the relationship between the credibility

of a nuclear security guarantee and support for nuclear weapons acquisition can

sometimes run in the opposite direction of what existing literature predicts. The

need for this alternative theory comes from insight that credible security guarantees

could backfire if leaders in the client state fear that their nuclear ally might mis-

calculate, either by using nuclear weapons in the absence of an attack by the client

state’s adversary or by being too quick to escalate a crisis or conflict to a nuclear

level. Unwanted use theory explains that credible security guarantees cause some

individuals to become concerned about unjustified or unfair use of nuclear weapons

by their ally. Those individuals then support nuclear weapons acquisition in order to

regain control over their nuclear fate.

The conventional wisdom and unwanted use theory are at odds in that they

explain two opposite reactions to nuclear security guarantee credibility. And yet,

the two theories can coexist, albeit in tension with each other, if each explains the

reactions of different segments of society in the client state. In early 2018, 68 percent

of South Koreans supported nuclear proliferation.

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How can the conventional wis-

dom and the unwanted use theory help explain this phenomenon? What does this

augur for other potential nuclear states?

To answer these questions, I design and analyze a survey experiment

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among a

representative sample of adults in South Korea. Survey respondents were presented

with scenarios that varied the credibility of the US nuclear security guarantee.

Respondents were then asked about their support for nuclear weapons acquisition.

I find a treatment effect whereby, on average, high-credibility nuclear security

guarantees increase support for proliferation, suggesting that the unwanted use

theory explains a larger proportion of citizens’ reactions to the credibility of nuclear

1012 Journal of Conflict Resolution 64(6)

security guarantees than does the conventional wisdom. In finding support for

unwanted use theory, I also offer an explanation of existing high levels of support

for nuclear proliferation in South Korea as well as challenge the wisdom of utilizing

nuclear security guarantees as a nonproliferation tool.

In the next section, I present the logic of the conventional wisdom on credible security

guarantees, demonstrating that it is incomplete. I then introduce th e logic of the unwanted

use theory, arguing that it explains the opinions of a segment of society ignored by

current theories. The following section examines the results of a survey experiment in

South Korea, concluding that the unwanted use theory explains how a large portion of the

public reacts to the credibility of nuclear security guarantees. This means that there is

pressure to proliferate both from individuals who view the nuclear security guarantee as

credible and from those who do not. This two-sided pressure presents difficulties not only

for American policymakers attempting to determine how to signal the credibility level of

the nuclear security guarantee but also for South Korean policy makers facing significant

public support for proliferation. Next, I test the mechanism of the unwanted use theory.

Finally, I conclude by ruling out alternate explanations of my results and by considering

the generalizability of the unwanted use theory.

Theories of Nuclear Security Guarantees

Conventional Wisdom on Nuclear Security Guarantee Credibility

The conventional wisdom argues that credible nuclear security guarantees can be a

replacement for nuclear weapons acquisition (Jo and Gartzke 2007; Sagan 1997;

Singh and Way 2004). The theory begins by assuming that threats to security are the

primary motivation for nuclear weapons acquisition. Fac ed with severe external

security concerns, the logic goes, a client state will choose to proliferate unless the

threat to its security ends or is averted. Credible nuclear security guarantees, whether

designed to deter the client state’s adversary and/or to reassure the client state that it

will be protected if necessary, prevent proliferation by accomplishing the same goals

that nuclear acquisition would—and at a lower cost (Monteiro and Debs 2014). The

following relationship is therefore expected:

Hypothesis 1: As the credibility of a nuclear security guarantee increases, support in

the client state for nuclear weapons acquisition will decrease.

But the mechanism that causes Hypothesis 1 cannot take place if the credible

nuclear security guarantee does not actually alleviate the cli ent state’s security

concerns—and there are important reasons to quest ion whether credible nuclear

security guarantees indeed improve security.

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Nuclear security guarantees can carry

their own security risks that undermine their potential reassuring power. Consider,

for example, the deployment of Terminal High Altitude Area Defense (THAAD) as

a token of the credibility of the US nuclear security guarantee in South Korea. The

move resulted in threats of sanctions from China and even suggestions (“China

Sukin 1013