East Asia’s Nuclear Drift: Why Didn’t East Asia Go Nuclear – Yet?
For decades, the central question of nuclear politics in East Asia was framed around a relatively straightforward hierarchical order: Could the United States effectively extend its nuclear deterrence to keep the region stable and its allies non-nuclear? Under the long-standing security guarantees from Washington, states like Japan and South Korea found it logical to forgo their own nuclear ambitions, trusting in a U.S.-led system that felt fundamentally durable.
That assumption is now under growing strain.
East Asia is not necessarily on the verge of a wave of nuclear proliferation. But the political foundations of the regional nuclear order are eroding. The erosion of this regional order isn’t driven by a sudden, singular desire for proliferation, but rather by the convergence of several destabilizing forces. We see an intensifying rivalry with the People’s Republic of China, which keeps expanding its nuclear and conventional capabilities, the relentless expansion of North Korea’s arsenal, and a renewed sense of nuclear coercion from Russia. Perhaps more unsettling is the “blurring of the lines,” in which the integration of cyberattacks against command-and-control systems alongside the rapid emergence of artificial intelligence-driven decision-making serves to dangerously compress strategic timelines, creating a volatile environment where the risk of misperception is significantly magnified.
In this entangled environment, Japan has always lived with a unique duality: the deep-seated moral weight of being the only nation to suffer atomic bombings, set against a practical, heavy reliance on the U.S. nuclear umbrella. While this balance once seemed manageable, the current deterioration of the regional threat environment has made it increasingly fragile. Debates over nuclear sharing, indigenous nuclear options, and alliance burden-sharing are no longer fringe discussions. They are becoming part of mainstream strategic discourse.
The shift matters because nuclear politics in East Asia is no longer just about who has the bomb. It is about how states respond when deterrence, reassurance, and competition begin to unravel at the same time. Nuclear sharing has become a language of reassurance. Proliferation has become a language of hedging. And strategic competition is the condition that gives both debates their force.
Japan captures this transformation especially well. It is the only country to have suffered atomic bombings on cities, the state most strongly associated with anti-nuclear norms, and, at the same time, one of the countries most dependent on the U.S. nuclear umbrella. For decades, that duality seemed manageable. Japan could champion disarmament internationally while relying on extended deterrence for its security. But a harsher strategic environment has made the balance harder to sustain. What emerges is not a simple contradiction, but a new kind of nuclear politics: one in which anti-nuclear sentiment remains strong, yet support for stronger deterrence measures grows as the regional threat environment deteriorates.
That does not mean Japan is about to go nuclear. But it does mean that the old assumptions underpinning East Asia’s nonproliferation order can no longer be taken for granted. The most important change is the nature of strategic competition itself. During the Cold War, deterrence debates often assumed relatively clear distinctions: between nuclear and conventional war, between strategic and theater-level conflict, and between separate geographic regions. Those lines are now blurred. Cyberattacks can disrupt warning systems. Space assets are integral to command, control, and communications. Precision conventional strike capabilities can threaten assets once assumed to be protected by nuclear deterrence. Artificial intelligence promises faster decision-making but also risks compressing timelines and magnifying misperception.
The result is a more entangled strategic environment in which crises may escalate not because leaders deliberately choose nuclear war, but because military operations in one domain are interpreted as preparing for escalation in another. A cyberattack on communications infrastructure, for example, may be intended as a limited conventional move. But if it affects early-warning systems or command networks, then it may be read as the prelude to a much larger strike. The danger is not only deliberate escalation. It is inadvertent escalation under conditions of ambiguity, speed, and mutual distrust.
This matters enormously for alliances. Extended deterrence has always depended on more than military capability. It rests on political confidence—the belief that the United States would in fact act decisively in a crisis, even at substantial cost. But in a more entangled environment, that confidence becomes harder to sustain. Allies must now ask not only whether the United States remains formally committed to their defense, but also whether it can manage simultaneous crises across regions, operate under cyber and space disruption, and maintain escalation control against multiple nuclear-armed adversaries at once.
That is why debates over nuclear sharing have returned. In Europe, nuclear sharing emerged as a way of binding allies more tightly into a common deterrent posture without requiring each to build an independent arsenal. In East Asia, however, the renewed appeal of nuclear sharing is less about operational necessity than about political reassurance. It reflects a fear that the old model of extended deterrence—strategic ambiguity backed by overwhelming U.S. superiority—may no longer be sufficient.
This is particularly true after Russia’s invasion of Ukraine. Moscow’s repeated nuclear threats reminded U.S. allies of an uncomfortable fact: nuclear coercion can shape a conflict even when nuclear weapons are not used. For countries in East Asia, the lesson was sobering. If adversaries can use nuclear signaling to raise the perceived costs of intervention, then formal alliance commitments may not be enough. What matters is whether the alliance can remain politically and militarily credible under nuclear-shadow conditions.
In that context, nuclear sharing becomes attractive not because allies are eager to cross the nuclear threshold, but because they want to reduce uncertainty. It is a hedge against decoupling. It signals that the ally is not merely a passive beneficiary of deterrence but a more integrated participant in it. That is why nuclear sharing is best understood not as proliferation by another name, but as a symptom of reassurance anxiety.
Japan’s domestic debate makes this clear. Japanese public opinion does not fit neatly into the categories often used by outside observers. The country is neither simply pacifist nor newly hawkish. It is, rather, ambivalent in a structured way. Public support for nuclear disarmament remains broad and genuine. Most Japanese still oppose the country acquiring its own nuclear weapons. The historical memory of Hiroshima and Nagasaki continues to exert real political force. But these same publics are also increasingly aware of the threat posed by China and North Korea and remain strongly supportive of the U.S.-Japan alliance.
That combination produces a distinctive pattern. As perceptions of regional threat intensify, support rises for stronger deterrent measures—including greater acceptance of extended deterrence and, in some cases, openness to discussing nuclear sharing. At the same time, support for actual Japanese nuclear armament remains limited, and support for nuclear use remains lower still. In other words, the public is willing to tolerate nuclear weapons as a shield, but not to embrace them as a normal instrument of national policy.
This is a crucial distinction. It suggests that Japan is not moving in a linear direction toward nuclearization. Instead, it is experiencing the political effects of strategic deterioration while still constrained by strong anti-nuclear norms. The country’s nuclear politics is therefore not a choice between disarmament and deterrence. It is an unstable effort to preserve both.
That instability should not be underestimated. If alliance confidence weakens sharply, or if regional crises become more frequent and more severe, the political space for nuclear hedging will expand. Debates that once seemed purely hypothetical could become more serious. And once nuclear options become normalized as topics of practical discussion, the nonproliferation order begins to weaken long before any state actually builds a bomb.
This is the broader danger facing East Asia. The proliferation challenge is no longer only about technology or intent. It is about the political conditions under which nuclear options become thinkable. States do not need to decide immediately to proliferate in order to destabilize the regional order. They need only begin to believe that the existing security system may not hold.
That is why the future of nonproliferation in East Asia will depend less on rhetoric than on reassurance. The United States and its allies cannot preserve the regional order through declaratory statements alone. They must demonstrate that extended deterrence remains credible under the conditions most likely to define the next decade: simultaneous pressure from multiple adversaries, attacks on critical networks, and a blurred line between conventional and nuclear escalation.
This points to a broader agenda than simple deterrence signaling. First, allies need stronger denial capabilities. In East Asia, deterrence will depend increasingly on the ability to prevent rapid faits accomplis and to sustain operations even under intense military pressure. For Japan, this means more resilient bases, stronger intelligence and surveillance capabilities, better logistics, stand-off strike capacity, and closer defense-industrial cooperation with the United States and other partners. These are conventional capabilities, but they are central to nuclear politics because they shape whether nuclear coercion will work.
Second, alliance consultation must become more institutionalized. Reassurance cannot depend on improvisation during a crisis. Allies need established mechanisms to discuss escalation risks, coordinate responses, and make decisions under time pressure. Without such mechanisms, the gap between formal commitments and political confidence will widen.
Third, East Asia needs practical risk-reduction measures suited to a more entangled environment. Strategic stability can no longer be understood only in the classic arms-control sense. It now also requires crisis communications, clearer signaling channels, and some degree of mutual restraint in cyber and space operations that could affect nuclear command-and-control systems. In an age of entanglement, risk reduction is not an alternative to deterrence. It is part of what makes deterrence sustainable.
Finally, nonproliferation itself must be updated. New technologies, from naval nuclear propulsion to advanced civilian nuclear systems, are changing the landscape in which states evaluate nuclear latency and strategic autonomy. The old nonproliferation order was built for a world in which the main challenge was preventing illicit weapons programs. The new challenge is preventing strategic competition from making nuclear hedging politically rational.
The stakes are especially high in Japan because the country still sits at the intersection of deterrence and disarmament. That position has often been described as a contradiction, but it is better understood as a political equilibrium—one that can hold only so long as both sides of the equation remain credible. If deterrence looks weak, pressure for stronger nuclear options will grow. If anti-nuclear norms are dismissed as naïve, one of the region’s most important restraints on proliferation will erode.
For Washington, the lesson is straightforward. A stable East Asian nuclear order cannot be preserved by asking allies simply to trust American commitments. Trust now depends on visible preparedness, alliance cohesion, and the ability to operate under severe stress. For Tokyo, the lesson is equally stark. Japan cannot rely on anti-nuclear identity alone to navigate a harsher strategic environment. It will need to strengthen its role within the alliance while resisting the temptation to let reassurance anxiety slide into nuclear normalization.
East Asia is not yet entering a nuclear age of rampant proliferation. But it is entering a more dangerous political era—one in which sharing, proliferation, and competition are no longer separate debates. They are different expressions of the same underlying problem: a regional order in which security guarantees are under strain, strategic rivalry is deepening, and nuclear weapons are once again moving from the background of politics to the center of it.
Nobumasa Akiyama is professor of international security at the School of International and Public Policy and the Graduate School of Law and Director of the Center for Disarmament, Science and Technology at the Japan Institute of International Affairs.
