Japan’s ‘Nuclear Taboo’ 80 Years after Hiroshima and Nagasaki

Summary

China’s rapid nuclear modernisation, including MIRVed ICBMs and tactical nuclear weapons, along with Russian nuclear signalling, has intensified Japan’s sense of vulnerability. At the same time, uncertainty over the long-term reliability of US security guarantees—even after renewed commitments—has fuelled calls for greater self-reliance.

Introduction

A recent poll by the Mainichi Shimbun sought the opinions of new entrants into the Japanese Diet regarding various issues. One question concerned the desirability of Japan ‘reintroducing’ a nuclear deterrent, either through the return of nuclear-armed United States forces or the development of an indigenous nuclear deterrent. Eight of the 125 new Diet members responded that they would like Japan to possess a nuclear deterrent. This is a significant rise in those favouring nuclear weapons, as against previous polls. Six of those in favour in the latest poll belong to the far-right Sanseito party, which has secured 14 seats in the Upper House of the Diet.^[1]

Japan’s experience as the sole site where atomic bombs were used as weapons of war has defined its post-World War II diplomacy, politics and indeed, its self-image. Its ‘three non-nuclear principles’, articulated in 1967, are a hallmark of its international standing. Japan has the unique honour of having two organisations deeply connected with its experience, and they have received Nobel Peace Prizes in the recent past.^[2] Yet it has now, in the person of its Prime Minister, a supporter of US extended nuclear deterrence, and a new far-right party in the Diet that explicitly calls for the creation of a domestic nuclear deterrent in its party manifesto. As such, questions have arisen around the durability of the country’s self-imposed ‘nuclear taboo’.

Japan’s ‘Nuclear Taboo’

Japan is the only country to have suffered an atomic bombing, making its experience sui generis. In August 1945, the United States targeted Hiroshima and Nagasaki with nuclear weapons, which killed over two hundred thousand people and injured several thousand. The experience of the devastating attack resulted in extreme anti-nuclear public perception in Japan. This is corroborated by an incident at the Bikini Atoll^[3] in 1954. A nuclear test blast of a 15 megaton hydrogen bomb created a widespread radioactive fallout affecting a Japanese ship, Fortunate Dragon (Daigo Fukuryū Maru), among others. The incident further triggered an anti-nuclear movement, which was already underway.

In line with these popular perceptions, Japan enacted the Atomic Energy Basic Law in 1955, which limits nuclear activities in Japan primarily for peaceful purposes. Article 2 of the Law states that

[n]uclear energy utilization is limited to peaceful purposes, to ensure safety, and is to be carried out autonomously under democratic management, and the results of this is to be made public, to actively contribute to international cooperation.^[4]

In addition to this legislative measure, Japan has also adopted a principled stand against the acquisition of nuclear weapons. In 1967, Prime Minister Eisaku Sato outlined three non-nuclear principles in the House of Representatives. These three principles are “not possessing, not producing and not permitting the introduction of nuclear weapons” on Japanese territory.^[5]

True to its principles, Japan has also consistently raised the issues of disarmament and non-proliferation at international forums. This is also reflected in their active membership in some of the most essential treaties related to weapons of mass destruction (WMD). Japan is signatory to the three main WMD treaties/conventions, i.e., Nuclear Non-Proliferation Treaty (NPT), Chemical Weapons Convention and Biological and Toxins Weapons Convention.

In addition, Japan signed and ratified the Comprehensive Test Ban Treaty (CTBT) in 1996.^[6] Tokyo has also contributed towards nuclear disarmament by partnering with the International Institute of Seismology and Earthquake Engineering to provide global seismological observation training courses since 1995. Subsequently, in the 2000 NPT Review Conference, Japan presented an eight-point proposal to advance the measures required for nuclear disarmament and non-proliferation concerns.^[7]

Factors Motivating Change in Japan’s Stance

Japan’s stellar record in nuclear non-proliferation has been complicated by its security environment, which has progressively worsened due to China’s moves to modernise its nuclear arsenal and the growing lack of faith in US commitments to defend Japan under President Donald Trump.

China’s Nuclear Modernisation

Although Chinese military and nuclear modernisation programmes are considered a counter to the United States’ military capabilities, they create significant consternation within Japanese strategic circles. The Chinese modernisation programme aims to enhance the reliability, survivability and effectiveness of its second strike capabilities. To achieve this objective, China has increased its nuclear arsenal, enhanced its delivery capabilities, and inducted more ballistic missile submarines.^[8]

China has invested heavily in increasing the number and sophistication of its Inter-continental Ballistic Missiles (ICBMs) and building more Multiple Independent Targetable Re-entry Vehicle (MIRV) warheads. These missiles are designed to penetrate missile defence systems, creating extreme vulnerabilities for Japan’s security. In one of the significant developments in recent times, China has reportedly^[9] developed tactical nuclear weapons (TNW), despite this being inconsistent with its no-first-use policy. The battlefield use of TNW gives China an additional advantage if it uses these weapons.

US’ Uncertain Commitment

Under the provisions of the Treaty of Mutual Cooperation and Security of 1960,^[10] the US is treaty-bound to provide external security to Japan, having restricted Japan to maintain only self-defence forces. The US has maintained a robust presence in Japan since the end of the World War II. However, the Trump Administration’s transactional diplomatic approach casts credibility concerns within the Japanese political and strategic community.

In February 2025, Prime Minister Shigeru Ishiba met President Trump in Washington for a bilateral summit. One of the key takeaways of the summit was the explicit commitment by the US side to use all means, including nuclear, to defend any moves by China on the disputed Senkaku Islands in the East China Sea. This marked the most overt commitment to deploy nuclear weapons made to the Japanese since the early days of the Cold War. However, it remains to be seen if President Trump implements this explicit commitment or reverts to his time-tested transactional vision of inter-state relations.

Japan’s Nuclear Readiness

According to nuclear experts,^[11] Japan has a ‘bomb in the basement’ policy wherein they have the material and the means to produce nuclear weapons within six months. This can be attributed to Japan’s advanced nuclear infrastructure. Japan is the only non-nuclear-weapon state (under the NPT) to have uranium enrichment and reprocessing facilities, which are an essential component for the complete nuclear fuel cycle. These facilities have been operational since the 1980s, helping Japan to amass a considerable amount of plutonium stockpile. At present, Japan has a stockpile of nearly 44 tonnes of plutonium, most of which is being reprocessed in the United Kingdom and France. Apart from this, Japan has a robust nuclear civilian programme with 11 operational nuclear reactors.^[12] This is a significant reduction in operational nuclear reactors, as 54 were active before the 2011 Fukushima Daiichi nuclear accident.

Japan also has a robust, multi-layered ballistic missile defence system to respond to ballistic missile attacks. To begin with, the Japan Self-Defence Forces conduct continuous round-the-clock surveillance. In case of a potential ballistic missile attack, it will instantly be detected by satellites and radars while predicting the impact point and missile trajectory. However, the ballistic missile defence system protecting Japan from incoming missiles is under the operational control of the United States, which, for reasons mentioned above, presents a quandary for strategic policymakers in Tokyo.

Domestic Dynamics

Incidentally, Prime Minister Ishiba’s preference for availing the services of US extended nuclear deterrence was well-known even before his summit with President Trump. During his election campaign in September 2024, Ishiba’s views on the necessity of a US nuclear deterrent on Japanese soil attracted attention, though he has since moderated his stance slightly.^[13] Calling himself a ‘realist’, Ishiba expressed public disagreement with survivors of the atomic bomb attack on Hiroshima and Nagasaki, who coincidentally won the Nobel Peace Prize for their efforts in 2024.^[14] He has also stated that the US’ nuclear umbrella should be a part of Japan’s defensive strategy, given modernisation efforts by China and sabre-rattling by Russia.^[15] His success in securing a nuclear deployment commitment from the US for the Senkaku Islands can be read as a signal success for his worldview.

The election of the far-right Sanseito to the Upper House adds to the view that Japan’s ‘nuclear taboo’ is under strain. The party goes further than Ishiba, as it openly espouses the need for Japan to develop an indigenous nuclear deterrent as part of its manifesto.^[16] Its position on this issue is driven by a broader opposition against the US military presence in Japan, which it seeks to have abrogated.^[17] As this party has only 14 seats in the upper house of a bicameral legislature, the extent to which it can affect legislation is currently severely limited. However, with Ishiba at the head of a minority government in both houses, a future issue-based coalition, with exploration of the possibility of starting a nuclear programme as a tradeoff (for a start), cannot be ruled out entirely.

Another key element of note is the relative isolation of Japanese policymakers, especially the permanent infrastructure, which is variously called the ‘iron frame’ or ‘deep state’, from the winds of public opinion. As a recent paper by two scholars clarifies,^[18] Japanese policymakers are relatively less accountable to the public when formulating policies, ensuring that even controversial policies placing significant burdens on the public can cross the legislative threshold into official policy.

One recent example is the effort mounted during Shinzo Abe’s early tenure to reinterpret Article 9 of the Japanese Constitution to allow for a national security infrastructure and the right to ‘collective self-defence’. When initially revealed, the new national security legislation attracted a hail of criticism and opposition from large sections of the public and the intelligentsia, who rightly comprehended the higher budgetary imposition placed on public finances. Demonstrations against the legislation and the Abe administration occurred almost daily.^[19] Nevertheless, the national security legislation emerged unscathed through the legislative ratification process, mainly due to internal compromise and support from key sections within the government.

Another example is immigration policy. The parlous state of Japanese demographics led sections of the policymaking elite to almost singlehandedly enact legislation on immigration relaxation and refugee recognition, after consultations with key business federations. Later on, refugee recognition procedures were tightened to address technical violations of certain sections of international humanitarian law in 2023, despite the hue and cry raised by a sizable number of civil society organisations and media outlets.^[20]

These examples indicate that if the perceived stakes are high enough, Japan’s policymaking apparatus appears willing to accept significant public opprobrium to achieve its goals. By this metric, it is reasonable to assume that the same apparatus would not hesitate to reject the non-nuclear principles to achieve nuclear breakout. The public would be forced to accept a fait accompli, and any negative political consequences may be deemed acceptable, since they would likely impact only elected officials. In fact, given the political quiescence of the Japanese public, it would be difficult to imagine any significant, sustained and violent opposition to Tokyo’s moves, even on such a sensitive issue.

Conclusion

China’s rapid nuclear modernisation, including MIRVed ICBMs and tactical nuclear weapons, along with Russian nuclear signalling, has intensified Japan’s sense of vulnerability. At the same time, uncertainty over the long-term reliability of US security guarantees—even after renewed commitments—has fuelled calls for greater self-reliance. Domestically, Prime Minister Ishiba’s advocacy for stronger US nuclear deterrence and the far-right Sanseito party’s push for an indigenous arsenal have normalised political debate on nuclear armament, challenging decades of consensus.

Therefore, there are grounds for concern that in the event of a future emergency, Japan’s policymaking elite, which has historically been relatively insulated from public opinion, could bypass popular anti-nuclear sentiment if strategic necessity is perceived. The nation’s advanced nuclear infrastructure, with a large plutonium stockpile and full fuel-cycle capability, means it could develop nuclear weapons within months, making the abandonment of the taboo more feasible than ever.

To be sure, at present Japan is staunchly committed to maintaining its traditional opposition to nuclear weapons. The deep network of non-proliferation initiatives in which it participates could also prove challenging to disentangle should it wish to change its stance. However, weakening a key pillar of that stance, namely, its normative commitment to non-proliferation and non-nuclearisation, offers significant cause for reflection, as Japan’s limitations have historically been entirely self-imposed. A significant loosening of normative restraint could fuel calls for pursuing technical potential, which would engender a substantial re-evaluation of East Asia’s overall security dynamics.

Views expressed are of the author and do not necessarily reflect the views of the Manohar Parrikar IDSA or of the Government of India.

^[1] 光田宗義 (Mitsuda Muneyoshi), “「核兵器保有すべきだ」8人　参政党躍進で急増　参院選・当選者分析” [Analysis of Newly-Elected Upper House Members: 8 Say Japan Should Possess Nuclear Weapons, Rapid Rise Caused by Sanseito Gains], Mainichi Shimbun, 1 August 2025.

^[2] “International Campaign to Abolish Nuclear Weapons – Facts”, The Nobel Prize, 14 August 2025; “Nihon Hidankyo – Facts”, The Nobel Prize, 14 August 2025.

^[3] “Japanese Fisherman and the Bikini Atoll H-Bomb Blast”, Association for Diplomatic Studies and Training (ADST).

^[4] “Atomic Energy Basic Act (Act No. 186 of 1955)”, Japanese Law Translation, Government of Japan, 19 December 1955.

^[5] “Statement by Prime Minister Eisaku Sato at the Budget Committee in the House of Representative(December 11th, 1967)”, Ministry of Foreign Affairs, Government of Japan, 11 December 1967.

^[6] “Japan Makes Voluntary Contribution to CTBTO to Enhance Tracking of Radioactivity”, Comprehensive Test Ban Treaty Organisation Preparatory Commission.

^[7] “Nuclear Disarmament and Non-Proliferation”, Ministry of Foreign Affairs of Japan.

^[8] Hui Zhang, “China’s Nuclear Weapons Strategy and Modernization Program”, International Network of Engineers and Scientists for Global Responsibility, Fall 2021.

^[9] The information is not confirmed. It is making rounds in media and international diplomatic circles.

^[10] “U.S. Security Cooperation with Japan”, The United States Department of State, 20 January 2025.

^[11] Robert Windrem, “Japan Has Nuclear ‘Bomb in the Basement’ and China Isn’t Happy”, NBC News, 11 March 2014.

^[12] “Japan­ Civil Nuclear Power”, International Trade Administration.

^[13] Shizuka Kuramitsu, “Japan’s New Leader Stirs Debate on Nuclear Sharing”, Arms Control Today, November 2024; “Address by Prime Minister ISHIBA Shigeru at the Hiroshima Peace Memorial Ceremony”, Prime Minister’s Office of Japan, 6 August 2025.

^[14] “PM Seeks Realistic Approach After A-bomb Survivors’ Group Wins Nobel Prize”, Kyodo News, 12 October 2024.

^[15] Junichi Fukuda, “Points to Keep in Mind When Discussing ‘Nuclear Sharing and Nuclear Introduction’; On the Subject of New Prime Minister Ishiba’s Claims”, Commentary, Sasakawa Peace Foundation, 11 October 2024.

^[16] Tohru Shirakawa, “Japan Antinuke Groups Criticize Sanseito Politician’s Call for Nuclear Armament”, The Mainichi Shimbun, 25 July 2025.

^[17] Shin Kawashima, “Sanseito: Japan’s Rising Party Doesn’t Trust America – or China”, Commentary, ThinkChina, 13 August 2025.

^[18] Lyong Choi and Yejun Kim, “The Convergent Evolution of Nuclear Strategy: The ROK and Japan’s Differing Paths to Nuclear Hedging”, The Pacific Review, 2025, pp. 1–29.

^[19] Yuichi Hosoya, “Historical Memories and Security Legislation: Japan’s Security Policy Under the Abe Administration”, Asia-Pacific Review, Vol. 22, No. 2, 2015, pp. 49–51.

^[20] Atsushi Yamagata, “Discursive Strategies to Legitimise Restrictive Approaches Toward Asylum Seekers: Controversial Bill to Amend Japan’s Immigration Act in 2023”, Journal of Intercultural Studies, 2025, pp. 1­2.