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This essay is the fourth in a series that examines the South Korean nuclear debate from regional perspectives.

It is often said that if South Korea were to go nuclear, it would trigger a domino effect, with Japan and Taiwan following suit.[1] But assuming that such a domino effect would easily take place is overly simplistic. Japanese public opinion against nuclear weapons – rooted in the history of Hiroshima and Nagasaki – remains strong enough to constrain policymakers. Education, of both the public and policymakers, plays a major role in shaping these attitudes, and could do so in South Korea as well. This paper first examines Japan’s potential response to a nuclear South Korea. It then discusses the role of education, with a critical analysis of Japan’s practices, and concludes with recommendations for advancing disarmament education that would be effective in South Korea and globally.

Japan’s double standard

To understand Japan’s potential response to a nuclear South Korea, it is helpful to first examine Japan’s double standard regarding nuclear weapons. On one hand, Japan advocates for a world without nuclear weapons, based on the recognition of the catastrophic humanitarian consequences of the atomic bombings of Hiroshima and Nagasaki in 1945. After World War II, Japan declared itself a “nation of peace” under its war-renouncing constitution, and continues to assert this identity. Since 1967, it has maintained the Three Non-Nuclear Principles: not possessing, not producing, and not permitting the introduction of nuclear weapons. Most people are aware of the devastation caused by the atomic bombings in Hiroshima and Nagasaki; nuclear weapons are thus generally regarded as “evil.”

On the other hand, Japan benefits from the United States’ extended deterrence, a fundamental component of the Japan-US Security Treaty of 1960. In response to North Korea’s nuclear and missile developments, as well as China’s military rise and expansionism, Japan started the Extended Deterrence Dialogue with the United States in 2010. Strengthening the credibility of US nuclear deterrence has been a key objective in Japan’s National Security Strategy since 2013.

Several opinion polls show that 60-70 percent of the public believe that Japan should join the Treaty on the Prohibition of Nuclear Weapons (TPNW), which entered into force in 2021. However, the government maintains its policy of neither signing nor ratifying the treaty, with less than 40 percent of National Diet members expressing their support for Japan joining it. A public opinion poll also shows that over 60 percent of respondents believe the US nuclear umbrella is “necessary” for Japan, at least “for the time being.”

The awarding of the 2024 Nobel Peace Prize to Nihon Hidankyo, the Japan Confederation of A- and H-Bomb Sufferers Organizations, has been warmly welcomed in Japan, further strengthening the nuclear taboo. This historic award has increased public pressure on the government to do more for nuclear disarmament, including attending future Meetings of States Parties to the TPNW as an observer. Notably, civil society groups in Japan have coordinated efforts across diverse sectors – labor unions, cooperative societies, lawyers, medical professionals, faith-based organisations, academics, students, and NGOs – overcoming past political and generational divisions. The Japan Campaign to Abolish Nuclear Weapons officially launched in April 2024 and is built on a broad coalition of over 35 civil society groups. It is now developing a nationwide, supra-partisan campaign to pressure the government to join the TPNW.^[2]

What if South Korea goes nuclear?

Japan’s dual stance must be fully examined in order to assess how Japan might respond to South Korea’s potential nuclear armament. The Japanese public, which generally opposes nuclear weapons, would be dismayed at the emergence of a new nuclear-armed state just next door. Moreover, South Korea cannot go nuclear without withdrawing from or breaching the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), one of the most universally accepted legal bases of today’s international order. Such a move would be viewed as a serious challenge to United Nations-centered multilateralism, which Japan continues to regard as essential for maintaining international peace and security.

At the same time, it is important to acknowledge that an increasing number of Japanese politicians, including leading lawmakers, have recently discussed the idea of Japan’s “nuclear sharing” with the United States, or even Japan’s potential independent nuclear armament. In the aftermath of the 2011 Fukushima nuclear disaster, some politicians argued that Japan should not abandon nuclear power in order to maintain a “potential nuclear deterrent.”^[3] Ishiba Shigeru, who became Japan’s Prime Minister on 1 October 2024, was one of those politicians, although he made it clear that he did not support Japan becoming a nuclear-armed state.

Nuclear sharing?

In 2022, soon after Russia’s military invasion of Ukraine, the late former Prime Minister Abe Shinzo called for a “discussion” on the possibility of Japan engaging in nuclear sharing. Some political factions responded positively to this idea, but then-Prime Minister Kishida Fumio firmly rejected it, stating that Japan’s Three Non-Nuclear Principles will be “firmly” upheld.^[4]

Nuclear sharing became a topic of debate during the Liberal Democratic Party (LDP)’s presidential election in September 2024. The LDP, Japan’s dominant political party, which has governed the country almost continuously since the 1950s, saw several of the nine candidates explicitly refer to the possibility of nuclear sharing with the United States and the potential revision of the Three Non-Nuclear Principles. These candidates included Ishiba Shigeru, who won the election, and Takaichi Sanae, who finished a very close second. During the party’s election campaign, Ishiba argued that nuclear sharing with the United States by “taking part in the decision-making process of the use of nuclear weapons” would not be incompatible with the Three Non-Nuclear Principles, which prohibit a physical “introduction” of nuclear weapons. Meanwhile, his competitor Takaichi went so far as to suggest an explicit revision of the Three Principles.

However, these debates do not mean that Japan is likely to pursue a nuclear sharing arrangement with the United States, even if regional tensions further worsen. In fact, since becoming Prime Minister in October 2024, Ishiba has not spoken about nuclear sharing or the “Asian version of NATO” that he had previously advocated for.^[5] In any case, it is the United States that holds the decisive power in determining any nuclear sharing arrangements. Japan could not share or introduce US nuclear weapons unless the United States deemed it in its own interest and actively pursued such a policy. Moreover, even if the United States were to do so, it is highly questionable that the Japanese public would readily accept it, as public opinion polls consistently show that 70-80 percent of Japanese believe that the Three Non-Nuclear Principles “should be maintained.”

Conflicting historical recognitions in Japan and Korea

As mentioned above, the nuclear taboo remains deeply embedded in the collective consciousness of the Japanese public. This sentiment stems from repeated exposure to the horrors of the atomic bombings of Hiroshima and Nagasaki, whether through school education, books, comics, television programs, or other mediums, cultivating a strong self-identity among Japanese citizens as members of an “atomic-bombed nation.”

In contrast, despite tens of thousands of Koreans also being victims of the atomic bombings of Hiroshima and Nagasaki, South Korean society has not developed a similar nuclear taboo rooted in historical experience. Instead, there is an underlying perspective in South Korea that permits some acceptance of the utility of nuclear weapons. Many South Koreans perceive that Japan’s surrender, prompted by the atomic bombings, directly led to Korea’s liberation and independence. This view, which regards the atomic bombs as instruments of Korea’s liberation from Japanese occupation, carries a dangerous implication: it risks encouraging a broader acceptance of nuclear weapons as useful tools in today’s world.

To counter the rise of pro-nuclear sentiments in South Korea, establishing a nuclear taboo similar to that in Japan is necessary. However, as noted, emphasising the tragedies of Hiroshima and Nagasaki in South Korea – where perspectives on the bombings differ – may instead provoke resentment or opposition toward Japan. The strong dissatisfaction among South Koreans regarding the Japanese government’s reluctance to fully acknowledge its role as an aggressor must be understood by Japan.

To move forward, Japan–both its government and society–must confront its history as an aggressor with sincerity to bring about lasting historical reconciliation. Moreover, there is an urgent need for both Japan and South Korea to cultivate a deeper, more universal understanding of the inhumanity of nuclear weapons that transcends regional views and extends to a global context. This effort includes reexamining the atomic bombings of Hiroshima and Nagasaki as shared human experiences that highlight the inherent inhumanity of nuclear weapons.

Role of disarmament education

One effective way to foster a shared understanding between Japan and South Korea of the inhumanity of nuclear weapons is through disarmament education. Beyond merely disseminating knowledge on nuclear issues, disarmament education is an empowering process that equips individuals with critical and logical thinking skills while instilling a shared commitment to universal values values that respect the life, safety, and dignity of every person.

While education is often associated with schools, disarmament education is not limited to formal school settings; it is designed to reach people of all ages and backgrounds. Therefore, alongside structured programs for children and youth whether through school curricula or non-formal initiatives – there is a need to expand informal educational opportunities. These efforts should aim to engage parliamentarians, local government officials, educators, media, NGOs, and other individuals directly involved in security and disarmament dialogues.

The importance of disarmament education has been emphasised repeatedly in various international documents, where it is recognised as a shared priority. Both the Japanese and South Korean governments have consistently supported these initiatives through United Nations resolutions, NPT Review Conference agreements, and other international commitments.

However, the implementation of disarmament education in both Japan and South Korea remains insufficient, with each country facing distinct challenges in this area. In post-World War II Japan, “peace education” – focusing on the tragedies of war and the atomic bombings – has been widely promoted, largely due to the efforts of teachers’ unions. These unions became passionate anti-war and anti-nuclear advocates, motivated by remorse for sending their students to war. Such education has instilled a strong peace consciousness among younger generations by sharing the stories of those who suffered from the war, including the hibakusha, or atomic bomb survivors. While effective in fostering a deep aversion to nuclear weapons and war, questions persist about whether this approach has adequately equipped individuals with the necessary knowledge and skills for preventing war and building sustainable peace. Educational institutions, by focusing on Japan’s experiences as a victim, have largely neglected opportunities for students to critically engage with the broader context of wartime history – including Japan’s responsibilities as an aggressor in its colonial and wartime actions – and to reflect on how to prevent future tragedies. Additionally, students are rarely provided systematic opportunities to learn about current global nuclear issues or concrete pathways toward disarmament. There are also ongoing challenges in fostering critical thinking and proactive attitudes toward addressing these issues.

In South Korea, peace education has not been as widely promoted. This can be attributed in part to the relatively underdeveloped nature of anti-nuclear movements in South Korea, which has not served as a driving force for peace education in the way they have in Japan. Furthermore, peace education in South Korea has a very different emphasis: while Japan’s peace education focuses on the horrors of war and the atomic bombings, South Korea’s peace education is primarily framed within the context of promoting reunification on the divided Korean Peninsula. And, of course, the differing historical perspectives mentioned earlier cast a dark shadow over these efforts. Although both nations share a common awareness of the universal values underpinning disarmament, South Korean skepticism remains regarding Japan’s peace education, given Japan’s reluctance to fully address its wartime aggression.

Recommendations

While it is important to promote disarmament education that reflects each country’s unique circumstances, there are also significant areas where the two nations can and should collaborate. Through dialogue at all levels – among governments, civil society, experts and practitioners (especially educators), NGOs, and individuals – both countries can move toward greater mutual understanding and empathy for each other’s historical contexts. More effective approaches to disarmament education can be pursued by emphasising the following areas:

Nuclear Risk Assessment in Northeast Asia: In South Korea, awareness of the catastrophic impact of nuclear weapons use is relatively limited. While Japan has some degree of awareness rooted in the atomic bombing experiences, it is fair to say that the Japanese public also does not fully comprehend today’s nuclear threats. Disarmament education should therefore emphasise the realistic nuclear risks facing both countries, the potential humanitarian consequences of nuclear weapons use, and the importance of Japan-South Korea cooperation to mitigate these risks. Outcomes of the “Reducing the Risk of Nuclear Weapons Use in Northeast Asia” project – conducted collaboratively by the Asia-Pacific Leadership Network, Nautilus Institute, and Research Center for Nuclear Weapons Abolition, Nagasaki University (RECNA) – offer valuable case studies and quantitative assessments that can enhance these educational efforts.^[6]

Universalising the Inhumanity of Nuclear Weapons Use and Testing: To cultivate a shared understanding between Japan and South Korea on the inhumanity of nuclear weapons, it is important to underscore the indiscriminate suffering they cause, irrespective of nationality or ethnicity. During the atomic bombings, a large number of Koreans, including those who had been forcibly brought to Japan, were present in both Hiroshima and Nagasaki. Although the precise number of Koreans affected remains unknown, estimates range from 25,000 to 50,000 in Hiroshima and 11,500 to 20,000 in Nagasaki.^[7] What is clear, however, is that a significant number of Koreans lost their lives in these tragedies.

Additionally, over 2,000 nuclear tests conducted by nuclear-armed states have inflicted widespread harm globally, underscoring the need for continued investigation and support for those affected. In this regard, South Korean civil society has a vital role to play in examining the impacts of North Korean nuclear tests.

By expanding the focus beyond the specific Japanese narratives of Hiroshima and Nagasaki, nuclear weapons can be framed as a universal issue. Nuclear testing, in particular, should be viewed as fundamentally incompatible with human rights, social justice, and environmental and ecological protection. Enhanced efforts by both the Japanese and South Korean governments to investigate and support victims of nuclear testing could also foster closer ties with countries that are parties to the TPNW.

Fostering a Mid- and Long-Term Vision for Change: In both South Korea and Japan, the belief in nuclear deterrence remains deeply rooted as a perceived pillar of national security. Disarmament education can play a key role in cultivating the ability to critically assess this reliance on nuclear-based security frameworks and exploring alternatives that do not depend on nuclear weapons. Rather than dismissing such alternatives as unrealistic or unattainable in today’s security environment, policymakers and citizens in both countries could benefit from sustained forums for discussion and vision-building toward a nuclear-free security approach. A promising example was the dialogue held at the Korean National Assembly in September 2024, organised by the National Assembly Futures Institute.^[8] This event brought together bipartisan representatives from both South Korean and Japanese parliaments, as well as civil society leaders, to discuss mid- to long-term visions for improved regional security, including the potential establishment of a Northeast Asia Nuclear Weapon-Free Zone.

Paving the Way for a Nuclear-Free Future in Northeast Asia

In an increasingly uncertain global security environment, where powerful states wield nuclear threats, calls for greater nuclear reliance in the name of national security are growing worldwide, especially in Northeast Asia. In this climate, advocating for the importance of education might seem like a distant goal. Yet, by harnessing the transformative potential of disarmament education, there lies a genuine opportunity to shift the awareness and actions of policymakers, opinion leaders, civil society, and individuals in both South Korea and Japan. A heightened awareness of the inhumanity of nuclear weapons will play a crucial role in curbing the rise of pro-nuclear arguments in South Korea. Furthermore, the broader impact of disarmament education can support both countries in moving beyond historical tensions, fostering mutual trust and building a foundation for dialogue on shared security challenges. This approach not only strengthens the security of both Japan and South Korea but also holds the potential to enhance regional – and ultimately global – security.

References

[1] See: Chung-in Moon, ‘Is Nuclear Domino in Northeast Asia Real and Inevitable?’ (Asia-Pacific Leadership Network, 1 October 2021), https://www.apln.network/projects/wmd-project/is-nuclear-domino-in-northeast-asia-real-and-inevitable, 29.

^[2] Japan NGO Network for Nuclear Weapons Abolition, https://nuclearabolitionjpn.com/english.

^[3] Chester Dawson, “In Japan, Provocative Case for Staying Nuclear”, The Wall Street Journal, 28 October 2011, https://www.wsj.com/articles/SB10001424052970203658804576638392537430156.

[4] “Kishida says Japan won’t seek nuclear sharing with U.S.”, Nikkei Asia, 28 February 2022,
https://asia.nikkei.com/Politics/International-relations/Kishida-says-Japan-won-t-seek-nuclear-sharing-with-U.S; Address by Prime Minister Kishida Fumio at the Nagasaki Peace Memorial Ceremony,” Prime Minister’s Office of Japan, 9 August 2022 https://japan.kantei.go.jp/101_kishida/statement/202208/ _00004.html.

^[5] Ishiba Shigeru, “The Future of Japan’s Foreign Policy”, Hudson Institute, 25 September 2024
https://www.hudson.org/politics-government/shigeru-ishiba-japans-new-security-era-future-japans-foreign-policy.

^[6] Research Center for Nuclear Weapons Abolition, Nagasaki University  (RECNA), The Project on “Reducing the Risk of Nuclear Weapons Use in Northeast Asia”, https://www.recna.nagasaki-u.ac.jp/recna/nu-nea_project2021-2023-eng.

[7] The lower estimate is drawn from The Atomic Bomb Disasters of Hiroshima and Nagasaki, a work jointly edited by Hiroshima City and Nagasaki City and published by Iwanami Shoten in 1979. The upper estimate, meanwhile, is based on figures provided by the Korea Atomic Bomb Victim Association in 1972.

^[8] National Assembly Future Institute, 3 September 2024,  https://nafi.re.kr/new/notice.do?mode=view& articleNo=8995.

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.

Image: Genbaku Dome in Hiroshima (Wikimedia).