Awakening Godzilla: Japan’s fading nuclear allergy and the perils of proliferation in the Indo-Pacific

When Ishiro Honda’s “Godzilla” first stalked across Japanese cinema screens in 1954, the monster was unmistakably a metaphor. Awakened and mutated by nuclear testing, Godzilla embodied the trauma of Hiroshima and Nagasaki and served as a cinematic warning to humanity. For Honda, the atom, once unleashed, produced consequences that could not be controlled. 

For seven decades, Japan heeded that warning. The world’s only nation to suffer atomic bombing in war codified its “nuclear allergy” into the Three Non-Nuclear Principles of 1967, no possession, no production, no introduction of nuclear weapons, and positioned itself as the moral centre of the global disarmament movement.

That allergy is now showing signs of remission, and the cure has been administered not by Tokyo but by Beijing, Pyongyang, and Moscow. 

To be clear, the nuclearisation debate in Japan remains peripheral. It is not the preferred route to security for Japanese policymakers, nor does it command majority public support. Hibakusha organisations, the governors of Hiroshima and Nagasaki, and much of the political establishment continue to push back forcefully against any dilution of Japan’s non-nuclear identity. But what is noticeable and what should concentrate minds in Canberra, Washington, and beyond is how far the Overton window has shifted in a remarkably short time.

Recall the late Prime Minister Abe Shinzo’s carefully hedged intervention in 2020, in which he suggested that Japan should begin discussions about having discussions on nuclear sharing arrangements. It was a taboo-breaking statement at the time, wrapped in so many layers of qualification that it could be disavowed at will.

Contrast that with Defence Minister Koizumi Shinjiro’s declaration this year that nuclear weapons are a subject Japan “cannot avoid touching,” and that Tokyo must debate all policy options “without taboos” in light of the deteriorating regional security environment. A sitting defence minister, invoking France’s post-Ukraine nuclear posture and Finland’s shifting stance on nuclear introduction, has openly placed the Three Non-Nuclear Principles on the discussion table as the government revises its three key national security documents. What was once whispered at the margins of the Liberal Democratic Party is now spoken from the podium.

What explains this evolution? Three interlocking dynamics stand out.

First, the behaviour of Japan’s nuclear-armed neighbours. China’s rapid and opaque expansion of its nuclear arsenal, North Korea’s qualitative and quantitative advances in missile and warhead technology, and Russia’s repeated nuclear sabre-rattling over Ukraine have collectively demonstrated that nuclear weapons are not fading instruments of Cold War logic but active tools of coercion in twenty-first century statecraft. Japan sits at the geographic intersection of all three.

Second, an erosion of faith in US extended deterrence. Tokyo’s security has long rested on the credibility of the American nuclear umbrella, but transactional alliance politics in Washington, burden-sharing demands, and doubts about whether the United States would truly trade Los Angeles for Tokyo have introduced a corrosive uncertainty. Compounding this is the growing realisation that denuclearisation is unlikely to feature in any future US-North Korea deal. If Washington tacitly accepts Pyongyang as a nuclear weapons state in exchange for caps or freezes, Japan will live permanently under a North Korean nuclear shadow with no diplomatic exit.

Third, developments on the Korean Peninsula are quietly rewriting the region’s non-proliferation norms. Seoul’s push to relax the terms of its 123 agreement with the United States, securing expanded rights to uranium enrichment and reprocessing, alongside its agreement with Washington to acquire nuclear-powered submarines, may be framed as conventional deterrence within NPT obligations. But these moves inevitably raise suspicions of latent proliferation and lower the political cost for Japan to contemplate similar hedging. If South Korea can renegotiate the nuclear rules, Japanese strategists ask, why not Japan? 

Here the Godzilla metaphor acquires a darker, inverted meaning. In 1954, the bombs awakened Godzilla, and Godzilla warned against nuclear weapons. In 2026, it is Japan itself that is being awakened, slowly, reluctantly, but unmistakably, by the militarism and nuclear build-ups of its neighbours. Tokyo is a latent power, technologically capable of weaponisation within a short timeframe, stirred from decades of self-imposed restraint by forces beyond its shores. China, North Korea, and Russia, in failing to heed the original warning of the Godzilla story, risk curing Japan of its nuclear allergy, with all the unintended consequences that a proliferation cascade in Northeast Asia would entail. A nuclear or nuclear-latent Japan would likely accelerate South Korean ambitions, harden Chinese threat perceptions, and shred what remains of the NPT's credibility in the region.

None of this is inevitable, and none of it is desirable. Japan’s preferred and most credible path to security remains what it has been doing in deepening the US-Japan alliance, in investing in conventional counterstrike and denial capabilities, and in weaving the lattice-like network of partnerships with Australia, South Korea, the Philippines, and others that raises the costs of revisionism without crossing the nuclear threshold. The nuclearisation debate is a symptom, not a strategy.

But symptoms matter. The distance travelled from Abe’s discussions-about-discussions to Koizumi’s taboo-free debate is a measure of how badly regional deterrence architecture has frayed. Those who wish to keep Godzilla sleeping should look less at Tokyo and more at the behaviour that is waking him.

Stephen Nagy is Professor of Politics and International Studies at the International Christian University and a visiting fellow and the Japan Institute for International Affairs specialising in Indo-Pacific geopolitics and great power competition.