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The Peninsula

Detente or Degradation: Would ROK Nuclear Weapons Hinder or Facilitate Inter-Korean relations?

Published February 24, 2023
Author: Bo Ram Kwon

This piece is one of 12 contributions to KEI’s special project on South Korea’s nuclear armament debate that will run on The Peninsula blog over the next month. The project’s contributors include young, emerging, and mid-career voices, examining the debate from a historical, a domestic, and an international perspective. On Wednesday, March 15, KEI will host a conference featuring our various contributors’ work at our Washington, D.C. office and launch a compilation of all the pieces in a single, special KEI publication.

North Korea’s Nuclear Prowess and South Korea’s Threat Perception

South Korea’s nuclear threat perceptions have evolved over the years and took a noticeable turn in 2022. This was driven, mostly, by North Korea’s actions. Pyongyang has signaled its intention to further advance its nuclear and missile capabilities, including development of tactical nuclear weapons. In 2022, North Korea conducted an unprecedented number of missile tests, increasing the frequency and variety of delivery methods, which complicate South Korean and alliance interception capabilities. Furthermore, Kim Jong-un ruled out the possibility of denuclearization talks and rolled out a new nuclear policy law, which includes a provision for preemptive attack, lowering the threshold for nuclear use. Kim entered 2023 by announcing North Korea would “exponentially increase” its nuclear weapons as a goal for the year.

Against a growing nuclear threat from the North, intensifying U.S.-China strategic competition, and Russia’s flirtation with nuclear weapons in the war with Ukraine, South Koreans have indicated the need to take nuclear matters into their own hands. Polls in 2022 and early 2023 show steady or growing support for some form of nuclear armament, ranging from persuading the U.S. to redeploy tactical nuclear weapons on Korean soil to South Korea developing nuclear capabilities of its own. However, such support appears to be based upon vague or less-informed threat perceptions since public opinion surveys do not accurately factor in the costs and tradeoffs of going nuclear. Most surveys do not measure how such variables might undermine support. Academic research also provides evidence that public pressure to use nuclear weapons in an escalating crisis may not be as strong as anticipated. As a methodology, survey-based public opinion polls show distinct limitations in capturing voter attitudes towards nuclear options.

Although it has long been taboo to discuss South Korea’s nuclear armament at the government level, circumstances have changed since President Yoon Suk Yeol said South Korea could acquire its own nuclear weapons if the threat from North Korea increases. Yoon also said the U.S.-ROK alliance was discussing joint nuclear planning and exercises, but President Biden denied this, thus triggering further controversy about the level of trust between the allies and possibility of Seoul’s own independent effort.

It is challenging, if not impossible, to separate inter-Korean relations from South Korea’s respective relationships with the United States, China, and the broader array of international relationships surrounding the Korean peninsula. Nonetheless, this paper examines how South Korea could acquire nuclear weapons, namely, by pursuing nuclear latency or by developing its own nuclear arsenal, with primary emphasis placed on how this could impact inter-Korean relations.

Evaluating the Options for South Korea’s Nuclear Armament

Since late 2022, Korean and U.S. scholars and practitioners have begun to actively exchange views on the prospects of U.S. allies developing their own nuclear weapons. For example, at the first session of the KRINS-Brookings Joint Conference held on January 11, 2023, the moderator asked the audience for a quick show-of-hands on how they think South Korea should go nuclear. Among approximately 140 people, 43 voted for enhancing U.S. extended deterrence, 6 voted for redeployment of U.S. tactical nuclear weapons, 12 called for NATO-style nuclear sharing, 21 supported indigenous ROK nuclear armament, and 30 voted for building potential ROK nuclear capabilities. Though ad hoc and crude, this preference ranking is notable as the audience was mainly composed of retired military officers and civilian security experts.

Conferences like these were encouraged by U.S. expert recommendations to accept that North Korea has nuclear weapons and recognize some form of arms-control arrangement as the only realistic option to limit North Korea’s nuclear arsenal and missile systems. Others claim that “direct South Korean and Japanese deterrence is an increasingly better option,” so the nuclear debate should take its own course in East Asia. Reflecting these changes, countries in the Indo-Pacific region have resumed discussions about the nuclear dimensions of regional security.

South Korea’s ongoing nuclear armament debate revolves around several different pathways to “going nuclear,” including: strengthening the U.S. extended deterrence commitment; redeploying U.S. tactical nuclear weapons; establishing the alliance’s own NATO-style nuclear planning group; creating a nuclear sharing arrangement; or South Korea’s own effort to build nuclear latency or pursue a fully independent, indigenous nuclear weapons program. This paper examines the latter two potential pathways and how they could potentially affect inter-Korean relations.

Acquiring nuclear latency aims to empower South Korea in times of nuclear crises where North Korea is increasingly more likely to use nuclear weapons in the early stages. Benchmarking the case of Japan, this option enables South Korea to enrich and reprocess nuclear material via consultation with the United States. Because this is short of owning nuclear weapons, it is considered legitimate and eligible to avoid substantial sanctions and withdrawal of military assistance or condemnation from the U.S. and the international community.

In theory, having such breakout capacity could create a nuclear balance on the Peninsula, making détente via strengthened deterrence more likely. In practice, however, it would be difficult to expect improvement in inter-Korean relations. On one hand, ROK-U.S. relations will be strained since revising the cooperation agreement on the civil use of atomic energy is an uphill endeavor. The U.S. is reluctant to renegotiate the existing deal on the grounds that it adheres to the nuclear non-proliferation regime and the context of Japan is different from that of South Korea. This stance could undermine efforts to harness South Korea-Japan cooperation as well as trilateral security cooperation with the United States, and any sign of weakening alliance or inter-alliance cooperation could embolden North Korea. On the other hand, other allies and partners may also choose to pursue latent nuclear capacities and accelerate the arms race in East Asia. This would further incentivize North Korea’s militarization and hardly create an environment conducive to diplomacy in the region, which would further hamper inter-Korean relations.

Moreover, once South Korea acquires latent nuclear capabilities, it would be difficult to restart denuclearization talks with North Korea as evidenced by the demand for the denuclearization of the “Korean peninsula” and not “North Korea” per se. Given that much consultation between the ROK and U.S. would be required to even begin considering this option, it would be worthwhile to explore ways to shift the age-old denuclearization narrative towards one of “nuclear responsibilities.” This approach could serve two purposes. First, it could help persuade the United States to provide approval for greater nuclear latency. Second, it might help to bring North Korea back to the negotiation table.

Specifically, such an approach may help cultivate “security dilemma sensitivities” and nurture a shared understanding of nuclear responsibilities among and between nuclear and non-nuclear states. This departs from simply debating the “rights” to develop nuclear weapons or the “tradeoffs” of pursing one nuclear pathway over another. Instead, it shifts discussion towards elaborating and recognizing the unilateral and joint efforts needed to become a responsible nuclear state and contribute to nuclear governance. The introduction of such a narrative entails some risks of its own, including possible discussion of whether to recognize North Korea as a de facto nuclear weapons state and its far-reaching implications. It may even be viewed as naïve at a time when Russia has suspended its participation in New START and is shaking the nuclear non-proliferation regime at the core. At the bare minimum, however, it would relieve the pressure of reviving the denuclearization agenda yet possibly help restart negotiations without dismissing it as a whole.

Alternatively, South Korea could develop its own nuclear weapons. Setting aside the debate about the efficacy of this option, South Korea’s nuclear armament may create a balance of fear on the Korean peninsula that could enhance strategic stability. A nuclear South Korea would be free from concerns that the United States may not sacrifice San Francisco for Seoul when confronted by North Korea’s second-strike capabilities. Thus, North Korea may be convinced that South Korea would use its nuclear arsenal for its security and think twice before waging an attack. Some U.S. scholars argue that this option may also enable South Korea to effectively deter North Korea without straining relations with China. South Korea would no longer need to strengthen its security ties with the United States and thus cease to antagonize China, even offering an incentive to assist in engagement with North Korea.

However, whether South Korea’s nuclear armament would lead to détente or degradation in inter-Korea relations is uncertain due to the stability-instability paradox. It is possible that North Korea may become even more focused on its nuclear weapons program, muster all resources to further advance its nuclear arsenal, and diversify delivery methods for its tactical nuclear weapons. In other words, South Korea’s nuclear armament would exacerbate the challenges of an already untenable status quo. Furthermore, South Korea would be particularly vulnerable between when it withdrew from the NPT – which it would have to do to develop its own indigenous nuclear weapons program – and built a substantial and credible nuclear deterrent. The process could take up to several years. The prospect of North Korea entering into nuclear reduction talks would also diminish if South Korea is perceived as weak and North Korea capitalizes on the moment. What is more concerning is that since both Koreas are advancing preemptive strike capabilities and defense strategies, the probability of misperception and miscalculation that leads to nuclear crises may increase and hamper relations indefinitely. With so much uncertainty surrounding the nuclear armament option, it would be risky for South Korea to re-orient its national policy to support it.

Meanwhile, as South Korea becomes less susceptible to nuclear coercion from North Korea as well as neighboring great powers, it could begin to condemn China’s coercive behavior in a more upfront manner. Although strategic autonomy and decisiveness is much valued in international relations, such actions may disincentivize China to pressure North Korea to re-enter negotiations. Besides, if South Korea loses its moral ground by developing its own nuclear weapons and withdrawing from the NPT without mutual consent, its diplomatic capacity would be weakened. That is, its ability to harness the multilateral support needed to resume and sustain engagement with North Korea will be significantly reduced and inter-Korean relations will deteriorate accordingly.

Some advocates of South Korea’s nuclear armament offer scenarios in which South Korea embarks on developing nuclear weapons with the silent consent of the United States. In such a scenario, several steps would be introduced to create a nuclear balance on the Korean peninsula as well as induce nuclear disarmament after North Korea executes its 7th nuclear weapons test. This includes South Korea declaring it will withdraw from the NPT and pressuring North Korea to enter nuclear reduction negotiations. On one hand, the goal of realizing complete denuclearization is reduced to “pseudo” denuclearization to persuade North Korea. And, on the other hand, Seoul initiates discussions about forming a trilateral alliance between the ROK, United States and Japan. However, the multiple assumptions in this scenario make it hardly feasible, so evaluating its impact on inter-Korean relations is not likely plausible given the number of variables. However, there is value in sustaining the nuclear armament narrative as the shadow of North Korea’s miscalculation looms and South Korea needs to prepare against the absolute deterioration of U.S.-China relations that will be consequential to its national security.


As the Ministry of National Defense has set its goal for 2023 to enhance South Korea’s military capabilities and readiness while strengthening U.S. extended deterrence, the nuclear debate in South Korea has entered a new phase. As South Korea explores a range of nuclear options to maximize its national security, including developing its own nuclear weapons, it is important to navigate its North Korea policy to ultimately build a sustainable peace regime on the Korean peninsula. Focusing on South Korea’s nuclear latency or nuclear weapons development alone seems to create an imbalance between deterrence and assurance. Strong assurance mechanisms are needed to move any type of negotiations with North Korea forward.

In closing, the option to acquire latent nuclear capabilities or to develop indigenous nuclear weapons entails higher costs and responsibilities than benefits for inter-Korean relations. The current domestic debate about South Korea’s nuclear options is insufficiently backed by clear facts. Nor is it circulated widely enough among opinion leaders and the public to conduct a comprehensive analysis. Moreover, such discussions should not end in normative statements, but instead with practical policy recommendations and implications. At this juncture, a more robust and strategically directed domestic and international debate on the utility of South Korea’s armament could facilitate inter-Korean talks in unexpected ways. Given the urgency of the issue, the timing seems ripe for such a venture.

Dr. Bo Ram Kwon is Associate Research Fellow at the Korea Institute for Defense Analyses (KIDA). The views expressed here are the author’s alone.

Photo from Shutterstock.

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