International Institute for Middle East and Balkan Studies (IFIMES)[1] from Ljubljana, regularly analyses developments in the Middle East, Balkans and around the world. Dr. Masahiro Matsumura, Professor of International Politics and National Security at the Faculty of Law, St. Andrew’s University (Momoyama Gakuin Daigaku), and a member of the IFIMES Council, has prepared an article entitled “Nuclear Realism and Japan’s Choice: The Comparative Limitations of the Saudi Model and the Justification for Independent Nuclear Armament Under a ‘Three-Front Nuclear Threat’.” In his analysis, Dr. Matsumura presents a provocative structural-realist comparison of Saudi Arabia and Japan, arguing that fundamentally different security environments reverse the logic of nuclear restraint and make autonomous nuclear deterrence strategically compelling for Japan.
Recent analytical breakthroughs in strategic studies—most notably this author’s structural realist evaluation of Saudi Arabian nuclear restraint[2]—demonstrate that states forego sovereign nuclear armaments not due to legal adherence to non-proliferation norms, but as the result of a rational cost-benefit calculation grounded in external security arrangements, institutional guardrails, and strategic ambiguity. This article examines the applicability of the "Saudi Model" (the "Protected Hedger") to East Asia. It argues that due to fundamentally divergent geopolitical conditions, the structural mechanisms that enforce nuclear restraint in Riyadh cannot operate in Tokyo. While Saudi Arabia faces an incomplete, single-front nuclear threat from Iran within a region featuring friendly, nuclear-capable partners like Pakistan, Japan operates in an unprecedentedly hostile security environment. It is directly encircled by three active, mature, and expanding nuclear powers: China, Russia, and North Korea. Furthermore, the eroding credibility of U.S. extended deterrence under China’s anti-access/area-denial (A2/AD) conditions, coupled with the absence of regional nuclear allies, renders latent "nuclear hedging" strategically impotent for Japan. Reversing the realist logic of the Saudi model, this paper concludes that under Japan’s extreme "three-front" nuclear threat environment, sovereign nuclear armament represents the sole rational, autonomous mechanism to guarantee national survival.
The contemporary debate over nuclear proliferation has long been dominated by a tension between traditional non-proliferation legalism and catastrophic proliferation alarmism. In his groundbreaking pair of studies, Masahiro Matsumura dismantled this binary by articulating a realist framework for understanding nuclear restraint. Examining Saudi Arabia’s strategic calculus in the wake of the U.S.–Saudi Civil Nuclear Agreement[3] under Section 123 of the U.S. Atomic Energy Act[4], the 2025 Saudi-Pakistan Strategic Mutual Defense Agreement,[5] and the 2026 Mecca Joint Defense Agreement,[6] the author demonstrated that Saudi Arabia’s disinclination to build sovereign nuclear weapons is neither an artifact of normative devotion to the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) nor an indicator of strategic passivity.
Instead, Matsumura articulated what may be termed the Saudi Model of Structured Restraint: Riyadh refrains from crossing the nuclear threshold because its security environment permits it to derive effective, indirect deterrence through external security arrangements, bilateral surveillance frameworks, and strategic ambiguity at a fraction of the geopolitical, economic, and military costs associated with an indigenous bomb.
The primary purpose of this study is to subject the Saudi Model to a rigorous comparative test by applying its analytical apparatus to Japan. Can the strategic logic that sustains Saudi nuclear restraint operate in East Asia? Or does the structure of East Asian geopolitics invalidate the premises upon which the Saudi Model rests?
This paper posits that due to qualitative, structural, and existential differences in geopolitical threat environments, it is structurally impossible to apply the Saudi Model (the "Protected Hedger") to Japan. Whereas Saudi Arabia’s geopolitical environment renders external reliance rational and indigenous proliferation counterproductive, Japan’s extreme geopolitical environment—characterized by a direct, tri-directional encirclement by hostile nuclear-armed states—reverses the cost-benefit calculus. Consequently, for Japan, maintaining a non-nuclear posture under the assumption of U.S. extended deterrence is an irrational strategic anomaly; independent nuclear armament represents the only rational, realistic, and structural imperative for national survival.
To understand why the Saudi model fails in East Asia, one must first delineate its core mechanisms as formulated in the above two articles by this author. Traditional Western non-proliferation scholarship championed the "gold standard" (exemplified by the 2009 U.S.–UAE 123 Agreement[7]), which legally prohibited domestic uranium enrichment and spent-fuel reprocessing while requiring the IAEA Additional Protocol. In contrast, the U.S.–Saudi 123 Agreement abandoned this rigid, multilateral paradigm in favor of a transaction-based, dynamic risk management framework. By deploying U.S.-controlled "black-box" enrichment technology and national intelligence monitoring rather than relying exclusively on IAEA inspections, Washington retained direct technical leverage over Riyadh while accommodating Saudi Arabia's geopolitical balancing.
Furthermore, Saudi nuclear technology is constrained by an aggressive trilateral security architecture involving the United States and Israel. Section 622 of the U.S. Intelligence Authorization Act for Fiscal Year 2027 (Senate bill 4615)[8] is to institutionalize swift intelligence sharing between Washington and Tel Aviv regarding Saudi nuclear facilities. This structural feature guarantees that any Saudi attempt to divert civilian infrastructure toward weaponization would trigger immediate, unhedged military intervention by Israel or/and the United States, thereby raising the cost of sovereign weaponization to prohibitive levels.
Beyond bilateral U.S. ties, Matsumura incorporates the Saudi-Pakistan Strategic Mutual Defense Agreement and the Mecca Joint Defense Agreement among Saudi Arabia, Pakistan, and Turkey. Deterrence does not necessarily require a formal, Cold War-style U.S. nuclear umbrella. Because Pakistan is a nuclear-armed state, its explicit collective defense obligations to Riyadh create a layer of "strategic ambiguity". Potential aggressors, namely Iran, cannot rule out Pakistani nuclear involvement in the event of an existential attack on Saudi Arabia. This indirect extended deterrence provides Riyadh with sufficient security coverage without incurring the diplomatic and economic penalties of an indigenous program.
Finally, the second author’s article[9] draws a vital distinction between nuclear hedging (developing civilian nuclear infrastructure, technical expertise, and a latent breakout option) and nuclear armament (building an operational nuclear arsenal). Supported by external security ties, a state can maintain a latent hedge indefinitely as a strategic buffer. Nuclear restraint persists because external deterrence prolongs the period during which the state feels no structural urgency to convert latent capability into functional weapons.
The viability of the Saudi Model depends entirely on the structural features of its regional system. When comparing the security environments of Riyadh and Tokyo, the structural divergence becomes absolute.
Saudi Arabia operates in a region where its primary adversary, Iran, has suffered severe degradation of its nuclear infrastructure due to kinetic operations by Isreal and the United States, separately or jointly. Tehran’s nuclear ambitions, while persistent, remain an incomplete, near-threshold threat rather than a deployed strategic arsenal. Furthermore, Saudi Arabia is embedded in a favorable regional matrix. To its east lies Pakistan, a long-standing military partner possessing a mature nuclear arsenal. The Saudi-Pakistan Strategic Mutual Defense Agreement and the Mecca Joint Defense Agreement institutionalize a collective defense architecture among Saudi Arabia, Pakistan, and Turkey. Riyadh does not need its own bomb because Pakistan’s nuclear shadow complicates the escalation calculus of any regional adversary.
In stark contrast, Japan occupies arguably the most precarious geopolitical position of any major state in the contemporary international system. Japan is directly surrounded by three revisionist, authoritarian, and fully armed nuclear powers:
First, the People’s Republic of China (PRC) is executing an unprecedented expansion and modernization of its nuclear forces, moving rapidly toward a land-, sea-, and air-based triad with hundreds of new ICBM silos, hypersonic glide vehicles, and theater nuclear weapons specifically tailored for regional denial in the Western Pacific. Second, the Russian Federation possesses the world’s largest nuclear arsenal and has explicitly integrated tactical and strategic nuclear coercion into its statecraft and regional warfare doctrines, operating nuclear-capable bomber patrols and maritime forces directly adjacent to Japanese sovereign territory. Third, the Democratic People’s Republic of Korea (DPRK) has completed the operationalization of its nuclear forces, possessing mass-produced, solid-fuel road-mobile ICBMs, MRBMs, and tactical nuclear warheads specifically designed to strike Japanese military installations, population centers, and U.S. bases in Japan.
Crucially, the threat facing Japan is characterized by simultaneity and irreversibility. Unlike Saudi Arabia, which faces a potential future nuclear power, Japan faces an immediate, fully realized, asymmetric nuclear encirclement.
Because Japan’s security environment is fundamentally different from Saudi Arabia’s, the three operational mechanisms of the Saudi Model—extended deterrence, regional security networks, and latent hedging—collapse when applied to East Asia.
The Saudi Model relies heavily on U.S. security guarantees and bilateral surveillance as a substitute for a sovereign arsenal. In East Asia, however, the structural credibility of the U.S. "nuclear umbrella" is eroding under the weight of strategic asymmetry. Extended deterrence operates on a core psychological premise: a potential aggressor must believe that the guarantor state will treat an attack on an ally as an attack on its own homeland. China and North Korea have developed mature, mobile, and highly survivable intercontinental ballistic missile capabilities capable of striking the U.S. mainland. Consequently, Japanese strategic planners must confront the classic decoupling dilemma: whether a U.S. President would risk the nuclear devastation of American cities to retaliate against a Chinese or North Korean nuclear strike on Tokyo, Osaka, or Kadena Air Base.
Furthermore, China has developed robust Anti-Access/Area-Denial (A2/AD) networks backed by "ready two-stage nuclear coercion". China, Russia, and North Korea possess the capacity to strike U.S. forward-deployed forces in Japan with tactical nuclear weapons while holding the American homeland hostage with ICBMs. This structural asymmetry renders U.S. extended deterrence radically less credible in East Asia than any U.S. commitment in the Middle East, where no regional power possesses homeland-striking ICBM capabilities.
In addition, Saudi Arabia successfully mitigates its strategic vulnerability by constructing a multilayered defense architecture with Pakistan and Turkey, thereby importing nuclear deterrence by proxy through its association with Islamabad. Japan possesses no such structural option. East Asia contains zero friendly, regional nuclear-armed states. The Republic of Korea is a non-nuclear state facing the exact same structural vulnerability and reliance on U.S. extended deterrence as Japan. Japan cannot replicate the Mecca Joint Defense Agreement because there is no regional, non-U.S. nuclear power capable of extending an umbrella over the Japanese archipelago.
Finally, while the Saudi Model posits that a state can satisfy its security requirements by maintaining a nuclear hedge without converting that hedge into an operational weapon, nuclear hedging offers zero immediate deterrence value against mature, deployed nuclear triads. A state cannot deter a nuclear-armed aggressor whose finger is already on the launch trigger by pointing to its civilian nuclear power plants, commercial plutonium stockpiles, or computer simulation capabilities. In a high-intensity crisis over the Taiwan Strait or the Senkaku Islands, an adversary facing a Japanese nuclear hedge encounters an incentive to strike preemptively to prevent that hedge from ever being weaponized. Thus, in the East Asian theater, latent nuclear hedging does not stabilize the security environment; rather, it invites crisis instability and preemptive counterforce targeting.
The ultimate divergence between Saudi Arabia and Japan lies in the mathematical inversion of their respective cost-benefit calculations regarding sovereign nuclear acquisition. A systematic comparison of these cost-benefit structures reveals why nuclear restraint remains rational for Riyadh yet suicidal for Tokyo.
For Saudi Arabia, acquiring an independent nuclear arsenal is a net-negative strategic proposition. The costs are immediate and catastrophic, including a severe rupture of military ties with Washington, exposure to kinetic strikes, and economic sanctions that would annihilate Crown Prince Mohammed bin Salman’s "Vision 2030" agenda. Because Saudi Arabia can secure adequate deterrence through its 123 Agreement with Washington, intelligence integration between Washington and Tel Aviv, and defense pacts with Islamabad, the added marginal benefit of an indigenous bomb is near zero, while the marginal cost is existential. Restraint is therefore the only rational policy.
For Japan, the variables in the cost-benefit equation are radically inverted. Japan’s acquisition of sovereign nuclear weapons would entail short-term costs, requiring withdrawal from the NPT under Article X, enduring diplomatic friction with Western partners, navigating international sanctions, and restructuring the U.S.–Japan Security Treaty. Weighing against these temporary friction costs, however, is the ultimate strategic value: the absolute preservation of national survival, sovereign independence, and territorial integrity.
Without an independent nuclear deterrent, Japan faces three catastrophic existential risks: first, nuclear coercion and forced capitulation over sovereign territory like the Senkaku Islands; second, the total loss of strategic autonomy, transforming Japan into a vassal state subject to neighboring nuclear dictates; and third, national extinction through unhedged nuclear strikes without the capacity for assured second-strike retaliation. In classical realist theory, national survival is the precondition for all other state activities. When weighed against the worst-case scenario of national extinction or nuclear subjugation, the diplomatic and economic costs of nuclear acquisition transform from prohibitive barriers into a necessary, rational insurance premium for state survival.
Herein lies the ultimate theoretical synthesis: the above two articles by this author do not disprove the necessity of Japanese nuclear armament; they paradoxically prove it. Matsumura established that states do not refrain from building nuclear weapons out of moral devotion to non-proliferation dogma, but because their security architecture renders nuclear acquisition unnecessary. By logical inversion, when a state’s security architecture fails to provide reliable protection, when it is directly surrounded by hostile nuclear powers, and when no alternative external mechanisms exist, structural realism dictates that the state must acquire independent nuclear weapons.
This study has subjected this author’s analysis of Saudi nuclear restraint to a comparative structural test. The findings demonstrate that the Saudi Model is nontransferable to East Asia due to structural asymmetries in threat perception, adversary capability, and regional alliance networks. While Saudi Arabia’s restraint is sustained by external reliance that is structurally unavailable to Japan, Tokyo's "three-front" encirclement by China, Russia, and North Korea renders extended deterrence highly suspect and latent nuclear hedging strategically ineffective. Consequently, the cost-benefit equation for Japan favors sovereign nuclear acquisition as the sole reliable mechanism to prevent nuclear coercion or state extinction.
To overcome its severe geopolitical vulnerabilities and establish a credible posture of strategic autonomy, Japan should pursue a phased, highly coordinated nuclear modernization strategy across three sequential stages:
In the immediate term (Phase 1), Japan should initiate confidential strategic talks with the United States to transition the alliance toward a formal, land-based Nuclear Sharing Architecture modeled on NATO’s Cold War arrangements. U.S. tactical nuclear weapons should be forward-deployed to Japanese Air Self-Defense Force bases under an explicit dual-key command framework, bridging the immediate extended deterrence credibility gap while preparing Japanese institutions for nuclear statecraft.
In the medium term (Phase 2), Japan must build its own domestic nuclear fuel cycle infrastructure outside of the 123 agreement because its civil nuclear program is a purely commercial enterprise subject to external non-proliferation pressure. Tokyo must explicitly recognize its civil infrastructure experience and technologies as a critical national security asset, institutionalizing fast-breakout protocols across defense and energy ministries.
In the long term (Phase 3), in the event of further erosion in U.S. global commitments or a major shift in Western Pacific force postures, Japan must exercise its sovereign right under Article X of the NPT to withdraw from the treaty. Japan should construct an independent, highly survivable nuclear force focused on sea-based second-strike capabilities via submarine-launched ballistic and/or cruise missiles deployed on large conventional submarines in the waters of Northeast Asia. By shifting its national grand strategy from passive reliance on an eroding umbrella to the deliberate construction of an independent nuclear force, Japan will fulfill the true imperative of structural realism: securing its survival through self-help in an anarchic international system.
About the author:
Prof. Dr. Masahiro Matsumura is Professor of International Politics and National Security at St. Andrew’s University in Osaka, and was a 2024 ROC-MOFA Taiwan Fellow-in-Residence at NCCU-IIR Taiwan Centre for Security Studies in Taipei. He is Member of IFIMES Council.
The views expressed in this article are the author’s own and do not necessarily reflect IFIMES official position.
Ljubljana/Osaka, 17 September, 2026
[1] IFIMES – International Institute for Middle East and Balkan Studies, based in Ljubljana, Slovenia, has Special Consultative status at ECOSOC/UN, New York, since 2018 and it’s publisher of the international scientific journal “European Perspectives”, link: https://www.europeanperspectives.org/en
[2] Masahiro Matsumura, "Strategic Realism Over Non-Proliferation Dogma: Why Saudi Arabia Is Unlikely to Go Nuclear." World Geostrategic Insights, August 6, 2026, link: https://www.wgi.world/strategic-realism-over-non-proliferation-dogma-why-saudi-arabia-is-unlikely-to-go-nuclear/. Masahiro Matsumura, "External Deterrence, Strategic Ambiguity, and Nuclear Restraint: Why Saudi Arabia Is More Unlikely to Pursue Independent Nuclear Weapons in the Medium Term." World Geostrategic Insights, August 16, 2026, link: https://www.wgi.world/external-deterrence-strategic-ambiguity-and-nuclear-restraint-why-saudi-arabia-is-more-unlikely-to-pursue-independent-nuclear-weapons-in-the-medium-term/
[3] United States and Saudi Arabia Reach Historic Nuclear Cooperation Agreement, link: https://www.energy.gov/articles/united-states-and-saudi-arabia-reach-historic-nuclear-cooperation-agreement.
[4] 123 Agreements for Peaceful Cooperation, link: https://www.energy.gov/nnsa/123-agreements-peaceful-cooperation
[5] Pakistan–Saudi Arabia: A mutual defence pact with nuclear shadows, link: https://www.icanw.org/pakistan_saudi_arabia_a_mutual_defence_pact_with_nuclear_shadows
[6] Saudi Arabia, Türkiye, and Pakistan Issue Joint Statement of the Makkah Al-Mukarramah Summit for Joint Defence, link: https://www.spa.gov.sa/en/N2649227
[7] Matsumura, “"External Deterrence, Strategic Ambiguity …,” op.cit.
[8] S.4615 - Intelligence Authorization Act for Fiscal Year 2027, link: https://www.congress.gov/bill/119th-congress/senate-bill/4615/text#toc-id5e415ea0f6344a03b0bba7730c82f923.
[9] Matsumura, ”External Deterrence, Strategic Ambiguity …,” op.cit.
