This essay summarises the findings of a series of essays that explore how regional states might react if South Korea acquired nuclear weapons.

A state’s acquisition of nuclear weapons is generally assumed to be driven most saliently by security considerations.^[1] South Korea, a latent nuclear power, appears to be the most obvious example. North Korea’s rapidly expanding nuclear and missile capabilities, combined with its extremely aggressive nuclear strike doctrines, are seen by South Koreans as an existential security threat.^[2] Public opinion surveys conducted over the past few years consistently record around 70% support for nuclear armament.^[3]

Undeniably, North Korea’s nuclear program is a strong driver of this increasingly vocal support for nuclear weapons. Proponents of nuclear armament in South Korea argue that nuclear weapons are essential to counter North Korea’s nuclear threat, which poses an existential security risk, and that the US nuclear umbrella cannot be trusted for protection indefinitely. Conversely, South Korean opponents of nuclear weapons contend that the US nuclear umbrella has effectively protected its allies since the Cold War, and there is no reason to doubt the reliability of both its security assurance and nuclear umbrella now. The US-South Korea alliance, along with close scientific, technological, and trade cooperation, are tangible evidence of the US commitment to South Korea’s security. Furthermore, the United States has strategic reasons to maintain its alliance with South Korea and protect it, due to South Korea’s strategic position in containing China.

Security concerns like the need to deter North Korea act as a driver of proliferation, while the protection offered by the US nuclear umbrella serves as a constraint on proliferation. However, there are other drivers and constraints influencing the South Korean population’s desire for nuclear weapons. One important constraint is the negative economic impact of proliferation, and one potential driver is the association between nuclear weapons and international prestige.

These two factors are evident in survey results. When asked if they would support nuclear armament despite economic sanctions from the international community, 63.6% still expressed support, indicating strong public backing for such a move, yet such results appear somewhat sensitive to survey design. Public opinion analysis by Sangshin Lee from the Korea Institute for National Unification (2023) found that when respondents were informed about the potential negative side effects of nuclear armament (e.g., economic sanctions, damage to the South Korea-US alliance), support fell to 35%.

International prestige also appears to play a role. A poll by the Chicago Council in 2022 found that support for nuclear weapons was strong, regardless of whether respondents believed South Korea was stronger militarily than North Korea or not.^[4] The poll also found relatively high confidence in the American security commitment to South Korea.^[5] South Koreans seem to place equal importance on “recovering nuclear sovereignty” and enhancing their international standing, underscoring prestige-related motivations. In the Asan poll, 33.7% of respondents stated that their support for South Korean nuclear armament was “to acquire nuclear sovereignty as a sovereign state,” and 33.4% chose “to enhance South Korea’s influence in the region as a nuclear-armed Great Power.” The Chicago Council poll from 2022, found that “[a]mong the 67 percent who favour a South Korean domestic nuclear weapons program over US deployment or no weapons, prestige was the second most important rationale (26%).”

These results suggest several assumptions on what South Korea would gain, or lose in terms of economic impact and international prestige.

Assumptions of economic impact

Opponents argue that developing nuclear weapons would not only strain South Korea’s relationship with the United States, undermining the United States nuclear umbrella and threatening the alliance, but the United States, Japan, the European Union, and China would also use every available means – legal and economic – to prevent South Korea from going nuclear. This backlash would have serious repercussions for South Korea’s economy, badly damaging its high-tech industries and global competitiveness. Opponents of nuclear armament also point out that nuclear armament is costly and dangerous. Developing and maintaining nuclear weapons would require significant financial resources, leading to opportunity costs for other sectors of the economy.

If South Korea decides to withdraw from the Non-Proliferation Treaty (NPT) and launch a nuclear weapons program, it would face international political and economic sanctions immediately and be expelled from export control regimes. This period, sometimes termed the “valley of nuclear development stage,” would present significant challenges for South Korea as a trading and allied nation. South Korea is highly dependent on external trade for its economic survival, and relies heavily on the ROK-US alliance for its security.

South Korea’s expulsion from the international nuclear market would be almost guaranteed. Leaving the NPT would isolate South Korea from the global nuclear market, making it impossible to export nuclear technology, engage in international nuclear energy cooperation, or import nuclear fuel. Since nuclear power generation provides about 30% of South Korea’s electricity, disruptions in nuclear fuel supply would severely threaten the country’s energy security. This, in turn, would jeopardise its energy-intensive export of semiconductors, steel, cars, and ships. Expulsion from the nuclear market, particularly at a time when carbon neutrality and energy security are crucial global priorities, would have significant negative impacts on South Korea’s economic and energy sectors.

Assumptions about prestige

Whether prestige is a driver or a constraint is a matter of debate. According to proponents, acquiring nuclear weapons would transform South Korea’s international standing, enhance its ability to negotiate with North Korea on equal terms, and provide leverage against the United States and China to take stronger action against North Korea.

Opponents argue that nuclear armament would instead lead to strong international backlash, tarnishing South Korea’s reputation as a responsible and model member of the international community. South Korea would risk being compared to rogue or problematic states such as North Korea, Iran, or apartheid-era South Africa, especially as South Korea’s pursuit of nuclear weapons would violate its non-proliferation commitments and norms. Although Article 10 of the NPT allows for withdrawal under certain circumstances, this clause has become largely obsolete since the NPT’s indefinite extension in 1995 and near-universal adoption. Any attempt to invoke it could label South Korea as a rogue state.

South Korea cares deeply about its international image and prestige, and South Koreans take great pride in their nation’s status as a “middle power.” President Yoon Seok-yeol has sought to promote South Korea as a “global pivotal state.” In an essay for Foreign Affairs, he argued: “South Korea should no longer be confined to the Korean Peninsula but rise to the challenge of being what I have described as a ‘global pivotal state,’ one that advances freedom, peace, and prosperity through liberal democratic values and substantial cooperation.”^[6] The roots of this concept trace back several decades and are closely tied to South Korea’s journey from one of the world’s poorest countries to one of the richest. This journey is a source of immense national pride in South Korea, where politicians use it to promote economic and cultural exports. Nuclear armament, opponents argue, would tarnish not only the South Korean economy, but the positive image that South Korea has built up, possibly setting it back by decades.

These arguments – common enough in the South Korean nuclear debate – make assumptions about the international community’s views and responses to South Korean nuclear armament. However, such responses remain understudied. For that reason, this volume investigates how South Korean nuclear armament might be viewed in the region, thereby allowing these assumptions to be scrutinised more closely.

A study on regional responses to South Korean nuclear armament

Understandably, much academic and policy work has focused on the security drivers behind South Korean support for nuclear weapons. This study explores prestige and economy-related impacts of South Korea’s nuclearisation. A study of this kind is necessary because Korean public opinion in favour of nuclear weapons seems to be partly driven by prestige-related factors and constrained by potential economic costs. Yet, despite these two factors being well-established in opinion polls and policy writings over the last decade, few studies have sought to explore either question in more detail. More specifically, how would other states view South Korea going nuclear, and how would they react? Is there any way for other states to influence South Korea to prevent it from going nuclear?

The essays in this study provide tentative answers from four regional states – the Philippines, Indonesia, Mongolia, and Japan – highlighting the ways that South Korea’s nuclear proliferation could impact its international prestige and economy.^[7]

The study purposefully focuses on four countries with which South Korea has good or relatively friendly ties, but no alliance relationships. It excludes the United States, whose policy on “allied proliferation” has become a hotly debated topic in Washington, where Jennifer Lind and Daryl Press, among others, have argued that the US decades-long policy of extending nuclear deterrence to prevent its allies from acquiring their own nuclear weapons may have outlived its usefulness.

It also excludes China, whose response to South Korean nuclear proliferation also remains understudied, but is likely influenced by China’s strategic competition with the United States. In one of the few existing studies, Tong Zhao and Jungmin Kang have argued that China’s response would depend on whether or not South Korea went nuclear with US approval. If Washington responded with harsh punishments, Zhao and Kang argue that “Beijing might have an incentive to apply less severe pressure than Washington on Seoul in order to move South Korea closer to Beijing.” However, if Washington sought to accommodate Seoul, “China would probably impose comprehensive economic sanctions on South Korea.”^[8]

In our view, with the possible exception of Japan, the “friendly” states – important partners of South Korea in many international and commercial endeavors – present a vastly different dynamic that deserves the attention of policymakers. Southeast Asian countries for example, have received little attention, despite their growing importance and geopolitical adjacence to Northeast Asia, and their normative and legal commitments to nuclear non-proliferation and disarmament. To our knowledge, the essay by Karla Mae Pabeliña in this study is the first analysis that assesses the potential response of the Philippines to South Korean proliferation, while Elaine Natalie and Andhika Prawira’s essay adds to a small body of work addressing Indonesia’s response.^[9] Likewise, the essay by Jargalsaikhan Enkhsaikhan is the first to situate the South Korean nuclear debate in the context of Mongolia’s small but normatively influential position in the region, as the only one-country nuclear weapons-free zone. Finally, Akira Kawasaki and Keiko Nakamura’s study on Japan challenges the assumption that Japan is a “nuclear domino,” and focuses instead on Japan and South Korea’s shared legacy of nuclear victimhood and how to build a cross-national movement of nuclear disarmament education.

The responses of South Korea’s regional partners offer a more rigorous test in the context of international normative, legal, and commercial frameworks. When push comes to shove, how far will these states go to contain South Korean proliferation? How do they reconcile their normative and legal positions, such as membership in the Treaty on the Prohibition on Nuclear Weapons, with their economic development imperatives?

Overview of findings

The findings of this study are not straightforward. Overall, the essays find that South Korea’s nuclear proliferation would be negatively received by policy elites and governments in the Asia-Pacific region. However, these governments are likely to be either unwilling or incapable of subjecting South Korea to bilateral economic sanctions, outside of any sanctions regime imposed by the UN Security Council, which they would implement. With the caveat that China’s response has not been assessed here, this finding challenges the common assumption that South Korea will have to ride out sanctions in the short term, but will be able to adapt in the long term. The findings in this volume suggest the opposite: in the short term, South Korea’s economic integration into the regional economy might even bolster its ability to avoid sanctions; the goodwill that South Korea has accumulated through its soft power might also lessen the blow of any reputational damage in the region. Even more concerning is the possibility that a state like South Korea acquiring nuclear weapons could legitimise their acquisition in the eyes of Southeast Asian publics, to a degree that a bona fide pariah state like North Korea does not. This tentative finding indicates that the risk of a nuclear domino effect reaching further south than Taiwan should not be excluded.

However, the South Korean economy faces immense headwinds in the coming decades, as its population decreases at the fastest pace in the world. Meanwhile, Indonesia is projected to rise to become the world’s fourth largest economy, and the Philippines is projected to be one of the world’s fastest growing markets through 2050.[10] Both countries will grow at a higher pace than South Korea for the foreseeable future. Any leverage that South Korea may gain from its integration into the world economy is likely to decrease over time, and that is before taking into account the potential response of China.

One sector of the South Korean economy that would be impacted in both the short and the long term by nuclear proliferation is the nuclear power and export industry – a key part of the Yoon administration’s global pivotal state strategy. Even if sanctions were limited in scope and duration, South Korean proliferation would likely lead to uncertainty among international customers who require long-term stability for the kind of capital-intensive projects that nuclear reactor exports entail, and even less demanding projects like feasibility studies would likely suffer too. This would be the case for energy cooperation with both Indonesia and the Philippines. The negative impact of the former Moon administration’s decision to phase out nuclear power on South Korean reactor exports is indicative in this regard.^[11] The impact on the nuclear energy industry in South Korea would be similarly negative. The ability of nuclear power to support South Korean heavy industries would also decrease over time. South Korea’s ability to switch over to fossil fuels, mostly imported from Russia and the Middle East, would be heavily curtailed. Russia would be sure to sanction South Korea to support its new North Korean ally. Oil shipments would likely be shipped through Southeast Asia, where they would fall under Southeast Asian nations’ UNSC sanctions enforcement, which this study does find support for.

Japan has a potentially unique role to play in preventing South Korean nuclear armament. The two countries have a shared history of nuclear victimhood: 30,000 Koreans were killed in the atomic bombings of Hiroshima and Nagasaki. However, the two countries’ understanding of this shared history differ. For many decades, Japanese civil society has cultivated a vibrant community of anti-nuclear activists; in South Korea, the stories of Korean atomic bomb survivors are not well-known, and the atomic bombings are at times even seen as tools of liberation from Japanese colonial rule. As Akira Kawasaki and Keiko Nakamura argue, the nuclear victimhood framing in Japan has not been conducive to self-reflection on the Japanese colonial and war-time legacy. Earnest reconciliation over historical issues between South Korea and Japan could open up space and opportunity to build a shared understanding of the humanitarian consequences of nuclear use, and help strengthen the nuclear taboo both in South Korea and Japan.

Finally, the findings of this study clearly reject the assumption that South Korea’s international prestige would be enhanced by nuclear acquisition. Both Mongolia and Indonesia would view South Korean nuclear weapons in the same light as North Korean weapons and might even regard Seoul as a rogue state. Moreover, Kawasaki and Nakamura argue that the Japanese people will be “dismayed” by South Korea’s decision to acquire nuclear weapons, rather than emboldened to pursue weapons of their own. Even the Philippines – the most ambivalent country assessed in this study – would view the action as “heralding the breakdown of the NPT,” rather than a complement to South Korea’s international status. While the prestige argument is generally used to argue that nuclear weapons would put South Korea on equal footing with North Korea, it is clear that any perceived status enhancement would come at a huge reputational cost. Nuclear weapons will thus have a net negative effect on South Korea’s international prestige.

Recommendations

To prevent South Korea from going nuclear, regional states must work to strengthen the non-proliferation regime, increase their awareness of the drivers and constraints of nuclear proliferation, and support inter-Korean reconciliation and dialogue to address Seoul’s security concerns.

Ensure a successful NPT RevCon in 2026: The most urgent priority is for all states to work toward a successful conclusion of the NPT Review Conference in 2026. Without an effective NPT regime, there will be no international legal basis on which to impose sanctions on South Korea through the UN Security Council, which will be the key international mechanism through which South Korea can be swayed from the path of nuclear proliferation. Moreover, the risk of a “nuclear domino” effect throughout both Northeast and Southeast Asia will increase significantly in the absence of the non-proliferation regime.

Increase awareness in the region: At the same time, a nuclear domino effect should not be considered a foregone conclusion; regional leaders should seek to strengthen nuclear disarmament education among regional populations to strengthen public resistance against calls for nuclear armament. Experts and civil society activists must also work to increase awareness in regional capitals about how the unresolved situation on the Korean Peninsula is creating the risk of a new and dangerous nuclear arms race. Decisionmakers need to understand how a Korean nuclear standoff would affect their own national interests and identify tools to convince South Korea that nuclear armament is not in its best interests either. Quiet diplomacy and leader-level statements on the importance of upholding the international non-proliferation regime would show regional leadership. The new Prabowo government in Indonesia, the latest country to join the TPNW, has a particularly important role to play in regional non-proliferation leadership.

Regional dialogue and partnerships with South Korea: Other US allies in the region should seek to enhance their strategic partnerships with South Korea. Ongoing efforts, especially in Japan, to shoulder a larger defence burden could also be helpful in ensuring that increasingly scarce US strategic resources can be focused on maintaining requisite security assurances to South Korea, reducing proliferation pressures in Seoul. In the long term, bringing the Korean Peninsula back on the agenda of regional dialogue mechanisms, such as the ASEAN Regional Forum or the Ulaanbaatar Process, could help facilitate inclusive dialogue, including inter-Korean dialogue, and help reverse the increasing salience of nuclear weapons in Northeast Asian national security policies.

Moving the debate forward

The essays in this brief volume represent an initial exploration of the potential economic and reputational consequences of South Korea’s potential nuclear choice. More detailed studies that model economic impact and systematically investigate public opinion in regional states could provide more perspectives to validate these findings, and more data for implementing the recommendations. The responses of China and European countries should also be considered. As the South Korean nuclear debate rages on, it behoves all sides to inform themselves of the complex dynamics that nuclear proliferation introduces in the Asia-Pacific and beyond.

References

[1] Scott Sagan, “Why Do States Build Nuclear Weapons? Three Models in Search of a Bomb,” International Security Vol. 21, No. 3 (Winter, 1996-1997): 54-86, https://www.jstor.org/stable/i323316.

[2] KNCA, “Law on DPRK’s Policy on Nuclear Forces Promulgated”, November 11, 2022,  https://kcnawatch.xyz/newstream/ 1662687258-950776986/law-on-dprks-policy-on-nuclear-forces-promulgated/; (Republic of Korea Ministry of Foreign Affairs, “Understanding the North Korean Nuclear Issue,” https://www.mofa.go.kr/eng/wpge/m_5474/contents.do.

[3] A survey by the Asan Institute for Policy Studies in May 2022, which tracked public opinion over an extended period, showed that 70.2% of respondents supported nuclear armament. A 2024 poll from the Korea Institute of National Unification found that support had decreased somewhat from its peak in 2021, but remained high, at 66%.

[4] Toby Dalton, Karl Friedhoff, and Lami Kim, ‘Thinking Nuclear: South Korean Attitudes on Nuclear Weapons’ (Chicago Council on Global Affairs, February 2022), 11.

[5] A too credible commitment of US extended deterrence could also be a driver of support for independent nuclear armament, see Lauren Sukin, ‘Credible Nuclear Security Commitments Can Backfire: Explaining Domestic Support for Nuclear Weapons Acquisition in South Korea’, Journal of Conflict Resolution 64, no. 6 (1 July 2020): 1011–42, https://doi.org/10.1177/0022002719888689.

[6] Seok-yeol Yoon, ‘South Korea Needs to Step Up’, Foreign Affairs, 6 April 2022, https://www.foreignaffairs.com/articles/south-korea/2022-02-08/south-korea-needs-step; the view that South Korea should take a central role in regional affairs is bipartisan, see: Joon Hyung Kim, ‘South Korea’s Strategic Autonomy: Maintaining Regional Stability Amid US-China Competition’ (Asia-Pacific Leadership Network, May 2024), https://cms.apln.network/wp-content/uploads/2024/05/Joon-Hyung-Kim_27-May.pdf.

[7] The essays were discussed at a workshop held in Seoul in October 2024.

[8] Tong Zhao and Jungmin Kang, ‘China’s Role in Shaping South Korea’s Nuclear Choice’, Global Asia 18, no. 1 (March 2023), https://www.globalasia.org/v18no1/cover/chinas-role-in-shaping-south-koreas-nuclear-choice_tong-zhaojungmin-kang.

[9] Lauren Sukin and Woohyeok Seo, ‘East Asia’s Alliance Dilemma: Public Perceptions of the Competing Risks of Extended Nuclear Deterrence’, Journal for Peace and Nuclear Disarmament 7, no. 1 (2 January 2024): 91–114, https://doi.org/10.1080/25751654.2024.2358596; Alexander M. Hynd, ‘Dirty, Dangerous… and Difficult? Regional Perspectives on a Nuclear South Korea’, Journal of Asian Security and International Affairs, (6 December 2024): 1-27, https://doi.org/10.1177/23477970241298756.

[10] ‘Indonesia Will Become the 4th Largest Economy in the World by 2030’, Wellington Capital Advisory, 26 January 2021, https://www.wca.co.id/post/indonesia-will-become-the-4th-largest-economy-in-the-world-by-2030; Marcus Lu, ‘Visualizing the Future Global Economy by GDP in 2050’, Visual Capitalist, 22 August 2023, https://www.visualcapitalist.com/visualizing-the-future-global-economy-by-gdp-in-2050/.

[11] Viet Phuong Nguyen, ‘Lights Out for South Korea’s Nuclear Export Ambitions’, The Diplomat, 17 August 2017, https://thediplomat.com/2017/08/lights-out-for-south-koreas-nuclear-export-ambitions/.

This paper was supported through a grant from the Heinrich Böll Foundation, and is part of a series that examines regional views of South Korean nuclear proliferation. The opinions articulated above represent the views of the author(s) and do not necessarily reflect the position of the Asia-Pacific Leadership Network or any of its members, or funders.