Report

Japan’s Strategic Future and Implications for the US-Japan Alliance

Examining Japan’s 2022 nuclear debate and its implications for the U.S.-Japan alliance with actionable recommendations for extended deterrence in Japan

By Yuki Tatsumi • Pamela Kennedy • Kenji Nagayoshi

Japan

February 28, 2024

The war in Ukraine that began in February 2022 and Russia’s nuclear coercion in the conflict have sparked a debate in Japan about the future course of its national security policy, including its nuclear future. The discussion was spurred by the late prime minister Shinzo Abe when he suggested that Japan begin to examine the concept of nuclear sharing with the United States in the same way that some NATO members do. While this debate was short-lived, primarily because the public showed little interest in breaking away from the country’s commitment as a non-nuclear power, it still triggered a shift in Japan’s defense policy, as evidenced by its 2022 National Security Strategy, which suggests further shifts can occur.

Introduction

The U.S.-Japan alliance has played a critical role in U.S. defense policy in East Asia since 1951. Continuing to adapt to the changing strategic environment in the region, the alliance remains a cornerstone of peace and stability in the Indo-Pacific and beyond 70 years later, despite tectonic changes in the international order, including the end of the Cold War and the Global War on Terrorism.

The evolution of Japan’s defense policy has been closely intertwined with that of the U.S.-Japan alliance. Indeed, in the last three decades since the end of the Cold War, Japan has made efforts to adapt to the dynamic strategic environment by reorienting its policies to play a greater role within the alliance. Such a reorientation began to accelerate when Shinzo Abe returned to the premiership for the second time in December 2012. The efforts to modernize Japan’s defense policy that Abe spearheaded under the policy of “Proactive Contribution to Peace” include the passage of the Act on Protection of Specially Designated Secrets (SDS Act) (2013), the adoption of Japan’s first National Security Strategy (2013), the relaxation of the restriction on defense technology exports (2014), and the enactment of the Legislation for Peace and Security and reinterpretation of Article Nine of its Constitution to allow Japan to exercise the right of collective self-defense under specific circumstances (2015).¹

Throughout this evolution, however, Japan’s approach to nuclear issues has remained constant. Heavily influenced by the 1945 atomic bombings of Hiroshima and Nagasaki and its identity as the yuiitsu no hibakukoku (only country to have ever suffered atomic bombings), Japan resisted the storage of U.S. nuclear warheads on its soil in the early years of the Cold War when the United States took Japan under its nuclear umbrella.² Prime Minister Eisaku Sato, despite being a huge proponent of Japan’s nuclear armament himself, codified this resistance as the “Three Non-Nuclear Principles” (3NP) in 1967, in which Japan vowed non-possession, non-production, and non-introduction of nuclear weapons on Japanese soil.³ With enduring public sentiment against nuclear weapons, these principles have become Japan’s kokuze (national policy) and formed the foundation of Japan’s approach to nuclear policy for decades, during which time it has emerged as a strong advocate for nuclear disarmament and non-proliferation.⁴

Since the mid-1990s, however, Japan’s nuclear policy has periodically come under question as a result of threats from its three nuclear neighbors—China, North Korea, and Russia. Threats posed by North Korea—which began with its first attempt to withdraw from the Nuclear Non-Proliferation Treaty (NPT) in 1993, recently aggravated by increasingly more frequent missile tests and the progress in its nuclear program—have been the most significant in the short term. However, Beijing’s modernization of its military and nuclear capabilities, coupled with its assertive behavior in the East and South China Seas, has made Japan prioritize on threats posed by China in the past decade.

Moreover, the ongoing conflict between Russia and Ukraine has further intensified Japan’s concerns regarding nuclear threats. For one, given the reality that Japan and Russia still have an unresolved sovereignty dispute over the so-called Northern Territories, Moscow’s seeming willingness to use nuclear weapons to threaten Ukraine and other states involved in the conflict has forced Japan to consider what the impact of a similar nuclear threat—from China, North Korea, or Russia—could mean for East Asia and its own national security. Indeed, it appeared to have reignited a debate on Japan’s nuclear option, particularly about whether Japan should begin to consider nuclear sharing and the storage of U.S. nuclear weapons on Japanese soil, as prompted by the late Prime Minister Shinzo Abe. Immediately following the Russian invasion of Ukraine, Abe commented that Japan should discuss the concept of sharing nuclear weapons with the United States as some members of the North Atlantic Treaty Organization (NATO) do, arguing that Ukraine would not have been invaded had they been a NATO member state.⁵ Such a concept was supported by former high-ranking Japanese officials, both civilian and military.⁶ While this debate is controversial and far from settled, it indicates a potential shift in Japan’s defense policy.

At a minimum, the war in Ukraine deeply informed Tokyo’s revision of three national security policy documents released in December 2022: National Security Strategy (NSS), National Defense Strategy, and Defense Buildup Program. These documents articulated the considerably heightened sense of urgency that Japan has developed in the past decade regarding its security environment. They acknowledged that “[t]he free, open, and stable international order, which expanded worldwide in the post–Cold War era, is now at stake with serious challenges” and identified China as “an unprecedented and the greatest strategic challenge in ensuring the peace and security of Japan.”⁷ Japan also announced a significant defense budget increase of approximately 65 percent, from ¥5.4 trillion in FY2022 to ¥8.9 trillion in FY2027, and the acquisition of so-called counterstrike capabilities by utilizing standoff missiles, such as upgraded Type 12 surface-to-ship missiles (12SSM) and U.S.-made Tomahawks.⁸

As Japan moves forward with its own effort to “fundamentally reinforce its defense capabilities,” the credibility of U.S. extended deterrence, including the U.S. nuclear umbrella, has increasingly been scrutinized in Japan.⁹ The experiences during the Trump administration—during which Tokyo was exposed to Washington’s transactional approach to U.S. alliances around the world, including with Japan—have raised concerns in Japan about the sustainability of U.S. leadership and its commitment to the alliance. In addition, the Biden administration’s response to the Russia-Ukraine conflict—ruling out direct military intervention even before the Russian invasion began and reiterating its position by implying the reason is Russia’s status as a nuclear power—has fueled further doubt about U.S. willingness to uphold alliance commitments.¹⁰

To be fair, the United States has engaged with Japan to address its concerns about the credibility of extended deterrence through discussions with Japanese officials in the Extended Deterrence Dialogue (EDD), held regularly since 2010; unofficial consultation throughout the Nuclear Posture Review (NPR); and 2+2 defense and foreign ministerial meetings.¹¹ Still, as China expands its nuclear capabilities, Tokyo worries about the credibility and technical effectiveness of U.S. extended deterrence in the region. Japan is uncertain about what exactly would trigger a U.S. military response—including the possibility of using nuclear weapons—and the impact of a conflict involving a security partner but not a treaty ally. With potential flashpoints in the region, such as the Taiwan Strait, East and South China Seas, and Korean peninsula, the credibility of U.S. extended deterrence—including nuclear deterrence—is crucial for Japan’s defense policy.

The implications of Japan’s defense debate, including its future nuclear options, can have a profound impact on the U.S.-Japan alliance. For instance, Washington may need to reassess its ongoing discussions with Tokyo regarding roles, missions, and capabilities to operationalize bilateral defense cooperation envisioned for the alliance. For instance, if Japan decides to move forward with nuclear sharing or allow U.S. strategic weapons on its soil, or if the Republic of Korea (ROK) acquires nuclear weapons indigenously or through a nuclear sharing arrangement, the force posture of U.S. Forces Japan would require reevaluation.

Moreover, the debate on Japan’s nuclear policy potentially has a deep impact on security dynamics in East Asia. China, for example, has always protested the discussion, arguing that it exposes Japan’s dangerous militaristic tendency that still lingers in the country.¹² In response to Abe’s call for discussions on a concept of nuclear sharing, China has urged Japan to fulfill its international obligations as a party to the NPT and to abide by the 3NP.¹³ Therefore, any sign of Japan moving away from the 3NP could be used as justification for further expansion of China’s nuclear forces, which have been on a steep upward trajectory for the past several years.¹⁴ Needless to say, North Korea will capitalize on such a development in Tokyo to continue its threatening behavior. Hence, it is essential for the United States to understand the debate in Japan over the future direction of its defense policy, including its nuclear future.

This report, heavily informed by the off-the-record interviews with civilian officials in the Japanese government as well as active duty and retired officers from the Self-Defense Forces (SDF) between February 2023 and August 2023, aims to explore their perspectives on the following questions:

How have the threat perceptions among the Japanese defense policy community, including civilian government, military, and private sector experts, evolved since 2013, when Japan’s first NSS was released?
How has the Russia-Ukraine conflict impacted Japanese thinking on the direction of Japan’s defense policy, including its own nuclear options?
Have the changes in their perceptions of the credibility of U.S. extended deterrence impacted their thinking? If so, how? If not, why not?
How do the answers to these questions impact the U.S.-Japan alliance?

None of the questions renders a simple answer, as the debate over these issues continues in Japan. However, by shedding light on the Japanese officials’ considerations in tackling the revision of Japan’s three key national strategy documents, the report seeks to offer a modest yet practical set of policy recommendations that the United States can use in engaging Japan to ensure the sustainability of Tokyo’s confidence in U.S. extended deterrence.

Background

Japan’s nuclear future—or the debate about it—has periodically become a subject of interest. When the debate surfaced in the past, it was often presented in rather simplistic terms: a choice of whether Japan should acquire its indigenous nuclear weapon capability. As a result, it had been met with counterarguments against Japan choosing to go nuclear. Such arguments include the following:

Japan, as the only country in the world that has been attacked by nuclear weapons, will never be able to overcome the psychological, emotional, and political hurdle of abandoning the 3NP;
Owning a robust indigenous civilian nuclear power capacity and weaponizing such a capacity require very different skillsets; and
The financial costs of going nuclear are too high for Japan.¹⁵

However, the ongoing Russia-Ukraine war appears to have changed the dynamic since it broke out in February 2022. In particular, commentaries such as the one by the late Prime Minister Shinzo Abe—who argued that Japan needs to seriously consider an arrangement similar to NATO’s nuclear sharing in the midst of Russia’s nuclear intimidation against the West—appeared as a sign that Japan may be on the cusp of starting a debate on its nuclear options.

Given such a circumstance, the Kishida government’s revision of the NSS and two accompanying defense planning documents published in 2022 were considered to have offered an opportune springboard for such a discussion. In addition, the publication of several books on nuclear issues seemed to suggest a growing interest in nuclear-related issues under the surface. These books include the Japanese translation of The Case for U.S. Nuclear Weapons in the 21st Century by Brad Roberts, who, as U.S. Deputy Assistant Secretary of Defense for Nuclear and Missile Defense Policy (2009–2013), served as Policy Director for the 2010 NPR and Ballistic Missile Defense Review.¹⁶

Public opinion on this issue has also considerably evolved over the past 20 years. For example, in a 2006 opinion poll, over 80 percent of respondents said Japan must maintain the 3NP, and nearly 50 percent were opposed to even discussing Japan’s nuclear options.¹⁷ Opinion polls conducted after the Russian invasion of Ukraine, in contrast, showed the Japanese public’s greater interest in discussing nuclear options. In a survey by the conservative Sankei Shimbun, over 80 percent of respondents said Japan should discuss nuclear sharing. ¹⁸ Even in a poll conducted by the liberal Mainichi Shimbun, 57 percent of respondents thought Japan should discuss nuclear sharing.¹⁹

Taken together, these findings seem to point to increased attention and apparent willingness among not only political leaders but also the public to discuss whether Japan should consider a new path for its nuclear policy, including entertaining the option of nuclear sharing or, at a minimum, should consider whether upholding 3NP can remain a viable policy option for Japan.

Key Findings

North Korea remains a source of concern for Japan in more immediate terms, but threats from China and Russia loom large

When it comes to threat perception, the Japanese public pays far greater attention to North Korea’s ballistic missile and nuclear weapons programs than China’s or Russia’s. This is the result of constant exposure to explicit threats from North Korea for nearly 30 years.

Since the first successful launch of North Korea’s No Dong 1 (Hwasong-7) medium-range ballistic missile that flew in the direction of Japan in 1993, North Korea has launched over 250, several of which flew over Japan and triggered the J-ALERT emergency warning system.²⁰ In 2022 alone, Japan witnessed over 70 North Korean missiles being launched—so many that some experts and policymakers are concerned that the public has become accustomed to North Korean missile launches and even sees them as a part of their lives.²¹ In April 2023, North Korea also tested a Hwasong-18 intercontinental ballistic missile with a solid fuel propellant for the first time, which demonstrated a critical upgrade that makes these missiles “easier and safer to operate” and harder to detect as they require less logistical support than missiles with liquid fuel propellants.²²

In addition to its ballistic missile tests, North Korea has so far conducted six explosive nuclear tests and is believed to have achieved several major advancements in its nuclear arsenal. For instance, Pyongyang claims to have developed a new Hwasan-31 nuclear warhead that is small enough to be mounted on a short-range ballistic missile (SRBM), such as KN-23, effectively serving as a tactical nuclear weapon that is capable of hitting vital U.S. bases in Japan, including Marine Corps Air Station Iwakuni and Fleet Activities Sasebo.²³ North Korea’s ambition to deliver tactical nuclear weapons discreetly to its adversaries in the region, including Japan, is reflected in the fact that the majority of the missiles North Korea has tested over the past four years are SRBMs, many of which were launched from transporter erector launchers, train cars, or underwater/ground nuclear silos.²⁴

Given the sustained and intensifying explicit threats it poses to Japan, it is not surprising that North Korea continues to grab the public’s attention and remains Japan’s immediate source of concern. However, several senior Ministry of Defense officials and former SDF chiefs pointed out that, although the threat from North Korea has facilitated deeper discussions in Japan about its defense, this also seems to have left many Japanese confused, as Japan’s defense discussion often revolves around North Korea while simultaneously considering China to be the primary threat. For instance, even though the debate on counterstrike capabilities (formerly known as enemy base strike capabilities) driven by Japan’s defense establishment was often centered on use against North Korea as an extension of the current ballistic missile defense, these policymakers had China in mind as the main target.

China’s growing aggressiveness has driven Japan’s threat perception in recent years

The 2022 NSS characterizes China as a “matter of serious concern” that presents an “unprecedented and the greatest strategic challenge” to Japan and the international rules-based order.²⁵ This is yet another piece of evidence that, even though North Korea is by far the most urgent short-term security threat to Japan, China is increasingly perceived as a serious threat to Japan through its aggressive activities in the region and beyond. Indeed, there is a near consensus among the interview participants that the Chinese threat is felt more acutely in Japan today. In fact, many interviewees discussed at length how their perceptions of threats from China have quickly worsened over the past several years.

To be fair, the Japanese public has for years held an unfavorable view of China. Opinion polls conducted by the Japanese government show almost no change in the public’s unfavorable view towards China between 2013 and 2022 (held by 80% of respondents in 2013 and 81.8% in 2022).²⁶

China’s continued and escalating aggressive military and Coast Guard activities in the East and South China Seas and around Japan have aggravated this trend. Indeed, they made the public aware that not only is China an unfavorable country for them, but that it also poses an existential threat to Japan. Furthermore, the Japanese public is increasingly aware that a conflict over Taiwan may be a real possibility. Such sentiment is also increasingly being shared among Japanese political leaders and the defense establishment in Tokyo; as former Prime Minister Abe commented in December 2021, “a Taiwan contingency is a contingency for Japan.”²⁷ The current and former officials interviewed for this research indicated their belief that the public’s heightened threat perception of China has contributed to public support for the government’s decision to acquire counterstrike capabilities in 2022 compared to 2017 during the last revision of the National Defense Program Guidelines, when the issue was much more divisive and politically sensitive.²⁸

Russia’s nuclear intimidation intensifies Tokyo’s concern

Interview participants were largely in agreement that the Russian invasion of Ukraine prompted a major shift in the Japanese public’s perception of the nation’s defense. Previously, defense policy debate in Japan often attracted criticism that such a discussion reminds people of the era before the Second World War when Japan was militaristic or that Japan was becoming belligerent. However, the Russian invasion of Ukraine is viewed by the Japanese public as a cautionary tale, and the public now acknowledges the significance of national security and nuclear weapons in deterring an adversary. Although Ukraine inherited nuclear weapons from the Soviet Union, it let go of them in the 1990s because it lacked the resources and expertise to maintain them.²⁹ This led to the belief that Ukraine would have been able to deter an invasion with nuclear weapons—a notion also shared by some U.S. policymakers—and encouraged some Japanese politicians and conservative members of the public to call for nuclear options.³⁰ Although the nuclear debate in Japan died out eventually, several interview participants noted that if Russia uses nuclear weapons in the war in Ukraine, whether directly against cities or against unpopulated areas, Japan would be reminded of its vulnerabilities in the region, and could seriously examine its own. Even though Russia is not the main source of security concern for Japan, Tokyo is closely monitoring the situation in the belief that, as Prime Minister Fumio Kishida often puts it, “Ukraine today may be East Asia tomorrow.”³¹

The 2022 nuclear debate in Japan was short-lived and did not lead to a broader discussion on Japan’s nuclear future

Despite heightened anticipation, the 2022 NSS did not mark a major shift in Japan’s domestic discussion on its nuclear future. For instance, the 2022 NSS reaffirmed Japan’s commitment to upholding basic principles of the exclusively national defense–oriented policy and observing the 3NP as a “peace-loving nation.”³² Put simply, the resurgence of the domestic debate over Japan’s nuclear future was short-lived.

One of the reasons for this short-lived debate was the unexpectedly low level of attention among both Japanese political leaders and the public. The 2022 nuclear sharing debate, following comments made by Shinzo Abe, was partly driven by a growing realization that war is a real possibility—particularly after Russia, a permanent member of the U.N. Security Council, threatened to use nuclear weapons during its unprovoked invasion of Ukraine. Although the debate caught national attention from both sides of the political spectrum, it faded out by that summer. Consequently, Japanese lawmakers from both the ruling Liberal Democratic Party (LDP) and opposition parties did not seem interested in discussing it further. This is largely due to three factors: the Japanese public’s lack of interest in policy discussions regarding nuclear weapons; LDP lawmakers’ realization that nuclear sharing would not work for Japan after academics explained it to them; and Prime Minister Fumio Kishida’s dismissive attitudes toward the debate. It is worth noting, however, that the Japan Innovation Party—a conservative and the second-biggest opposition party in the National Diet—is still calling for active discussions on nuclear sharing. Although they acknowledge the limitations of NATO-style nuclear sharing in contributing to Japan’s security and its compatibility with 3NP, they argue that such discussions would encourage Japan to think deeply about how it can be involved in decision-making in U.S. nuclear planning and operations.³³ Nevertheless, as the incumbent prime minister was elected from a Hiroshima constituency, the nuclear sharing debate is unlikely to resurface under his administration. It is also important to note that the People’s Liberation Army’s exercises around Taiwan in August 2022 in response to then-U.S. House Speaker Nancy Pelosi’s visit to Taipei did not restart the nuclear sharing debate.

Furthermore, the comments by some senior government officials interviewed for this project suggest that even the short-lived debates over Japan’s nuclear future—especially the one on nuclear sharing—may have been misguided by a lack of understanding of the nuances of deterrence and the meaning of “nuclear sharing.” For instance, Takeo Akiba—the current Secretary General of Japan’s National Security Secretariat and a strong proponent of Japan’s nuclear sharing option—has argued in the past that nuclear sharing similar to that of NATO would signal to China and North Korea that the decision to use nuclear weapons “lies with Japan, not the United States.”³⁴

However, the reality of the nuclear sharing between the United States and its NATO allies could not be further from what Akiba describes. In fact, nuclear weapons under NATO’s nuclear sharing arrangements remain in U.S. custody. The hosting countries can launch a nuclear mission only with explicit political approval from NATO’s Nuclear Planning Group and authorization from the U.S. president.³⁵ In other words, even if Japan had a nuclear sharing arrangement with the United States, it would not grant Japan the authority to make an independent decision about how the nuclear weapons on Japanese soil should be used.

Moreover, although the NATO model of nuclear sharing is not the only option for Japan, the nation will probably be unable to adopt any meaningful nuclear sharing. The NATO context for nuclear sharing is completely different—NATO’s nuclear sharing arrangement since the Cold War period has been intended for ground-based campaigns, and B61 tactical nuclear bombs are deployed on select NATO members’ dual-capable aircraft (DCA).³⁶ Forward deployment of such tactical nuclear weapons to Japan would not make strategic sense from an extended deterrence perspective, because the defense of Japan would comprise mostly sea- and air-based campaigns. However, if the United States had not deemed nuclear-armed sea-launched cruise missiles to be “no longer necessary” in the 2022 NPR, Japan would perhaps have been able to consider them a viable option for a potential nuclear sharing arrangement.³⁷

Additionally, NATO’s nuclear sharing arrangement has not necessarily provided realistic options even for its members, who are aware that using tactical nuclear weapons in campaigns would harm their own people and assets in their territory and that their leaders do not have veto power if the U.S. president decides to launch a nuclear attack. As a result, a nuclear sharing arrangement does not necessarily provide robust—if any—nuclear deterrence; rather, it carries greater significance as U.S. reassurance of its commitment to its alliance obligations.

Lastly, if Japan decides to adopt a NATO-style nuclear sharing arrangement with the United States, it will inevitably violate the NPT, particularly Articles I and II, which prohibit any transfer of nuclear weapons between nuclear-weapon and non-nuclear-weapon state parties.³⁸ Therefore, instead of reassuring, such a nuclear sharing arrangement could lead to the collapse of the NPT regime and could invite nuclear proliferation in the Indo-Pacific, heightening the level of risk for Japan. Additionally, as a result of Japan’s strong “nuclear allergy”—a term that sprang out of the debate over whether Japan should allow port calls by U.S. nuclear-powered submarines in the 1960s—the Japanese public would most likely not accept or tolerate the NATO model of nuclear sharing.³⁹

Beyond the practicality of Japan pursuing an arrangement with the United States that is akin to nuclear sharing, the challenge for Tokyo is that it is almost impossible to deepen the discussion on this issue without a clear understanding of what nuclear sharing entails, especially by policymakers and political leaders. As Japanese people often talk about nuclear weapons as an extension of nuclear disarmament debates, a level-headed debate needs to be led by experts who can explain salient facts to policymakers and the public. However, the politicians who openly entertain the idea of Japan seriously considering nuclear sharing as one of its future policy options—especially those who are of the post-1955 system generation—are short-sighted because they disregard the potential repercussions of Japan adopting such a policy for both regional security and global nuclear proliferation. Therefore, Japan should pursue an alternative approach to nuclear sharing to deepen the discussion in the context of how Japan can be assured of the credibility of U.S. extended deterrence.

Japan remains committed to nuclear nonproliferation for now, but further discussion on Japan’s nuclear future is necessary

Although the Russian invasion of Ukraine prompted discussions of the future of Japan’s security, including nuclear options, Japan appears to remain committed to its role as an advocate for nuclear nonproliferation and disarmament. This is especially the case under the current Kishida administration. Unlike Abe, who attempted to encourage discussion on Japan’s nuclear policy, Kishida did not allow his government to continue the discussion, calling it “unacceptable.”⁴⁰ The G7 Hiroshima summit reflected Japan’s dilemma as an advocate for nuclear nonproliferation and disarmament while continuing to rely on U.S. nuclear umbrella for its own national security.⁴¹ Unless North Korea significantly intensifies its nuclear intimidation against Japan, or Russia launches a nuclear attack against Ukraine, this stance of pursuing nuclear disarmament while relying on U.S. nuclear deterrence will likely remain even after the Kishida administration ends. However, several officials argued that this could change if Japan begins to allow port calls by non-U.S. nuclear-powered submarines, especially Australia’s SSN-AUKUS.⁴²

There was an overwhelming agreement among Japanese officials and experts that Japan needs to deepen the discussion on whether its current nuclear policy anchored in 3NP is sustainable. Many senior SDF officers, both active duty and retired, have pointed out that the avoidance of discussion on nuclear issues has impacted their operational planning, even at a hypothetical level. For example, nuclear weapons are not even discussed in tabletop exercises in Japan, which these officers consider problematic.

The reality is, however, that the vast majority of the public remains firmly opposed to Japan acquiring nuclear capabilities, whether in the form of a NATO-style nuclear sharing arrangement with the United States or by developing nuclear weapons indigenously. Their support to maintain Tokyo’s normative commitment to the 3NP remains solid. This sentiment is also shared by Prime Minister Kishida, who argues that his government does not plan to consider the option in accordance with the 3NP and the Atomic Energy Basic Act, which states that “utilization of nuclear energy is limited to peaceful purposes.”⁴³

Moving forward, Japan’s 3NP, especially the third “N” (no introduction), will likely be an important area of the nuclear discussion within Japan. Even among the experts and officials, there are disagreements over whether a nuclear-armed submarine making a temporary visit would count as an “introduction” of nuclear weapons. This is because there is no consensus on the precise definition of “no introduction,” including whether such an introduction must be semi-permanent.⁴⁴

Nevertheless, there seemed to be broad agreement among the officials and experts interviewed for this project that the 3NP, in reality, had likely weakened to “2.5NP” or “2NP” in practical terms. They pointed to a statement 2010 statement by then Foreign Minister Katsuya Okada: “if an emergency situation arises and Japan’s security cannot be assured without allowing a temporary port of call of nuclear weapons to Japan, the administration of the day will make a decision.”⁴⁵ They also pointed out that the fact that 3NP are principles—which means it is a declaratory policy but not legally binding—provides both Japan and the United States maximum flexibility to cooperate in extended deterrence during an emergency, including allowing U.S. nuclear-armed strategic bombers to land in Japan.

In addition, even if Tokyo agrees to introduce U.S. nuclear-armed Ohio-class ballistic missile submarines (SSBNs) or strategic bombers for extended deterrence, the local government, adhering to the hikaku Kōbe Hōshiki (non-nuclear Kobe Method), can refuse to follow the central government’s direction—at least during peacetime—which can potentially delay joint action and render efforts ineffective.⁴⁶ Even during the 1995 Great Hanshin-Awaji earthquake that killed over 6,400 people and destroyed nearly 105,000 homes, the Kobe city government hesitated to welcome U.S. Navy vessels when offered, citing that the city ordinance requires a confirmation that a foreign navy vessel is not carrying nuclear weapons.⁴⁷

Japanese confidence in the alliance remains key to its nuclear future, but the sustainability of U.S. commitment has been questioned in recent years

While there is much debate on the issues stemming from temporary visits of nuclear-armed aircraft, some of the interviewed experts emphasized that excessive focus on the nuclear option is counterproductive. They believe it distracts attention from more important discussions of how U.S. extended deterrence will be implemented and how Japan can provide support through new and existing frameworks, such as the EDD. In fact, most Japanese officials and SDF officers seem satisfied with how the EDD, which was launched in 2010 as the United States revised its NPR, has evolved since.⁴⁸ Still, there is acknowledgment that the EDD still has room for improvement. For instance, the EDD is currently led by U.S. deputy assistant secretaries and Japanese deputy directors-general, which some critics point out is not senior-level enough to raise visibility and thereby publicly provide the appropriate level of political assurance. Elevating the EDD to the sub-cabinet level, for instance, would attract greater public attention and send a strategic message to China immediately with less risk of raising tensions.

Thus, discussions in the EDD must also cover planning, including how the U.S. would implement extended deterrence and how and when the United States would show up to assist Japan in a crisis. The United States and Japan should also consider the possibility of incorporating a new consultative body into the U.S.-Japan EDD, one similar to the U.S.-ROK Nuclear Consultative Group (NCG) announced with the Washington Declaration in April 2023.⁴⁹ Many Japanese government officials noted that it is too early to assess the NCG’s effectiveness and that they are not interested in any aspect of the NCG. Still, such a forum would allow Japan to take part in planning discussions and decision-making in nuclear operations, and the two countries would be able to link operational planning of conventional and nuclear forces. Thus, an NCG-like forum deserves consideration through careful observation of the NCG’s performance.

Another existing arrangement overseas that some experts say Japan could adopt is NATO’s Support of Nuclear Operations with Conventional Air Tactics (SNOWCAT) program, through which seven members that do not host U.S. nuclear weapons can provide operational support to nuclear-armed DCAs.⁵⁰ SNOWCAT missions include escorting DCAs, aerial refueling, suppression of enemy defenses, and search and rescue of downed DCAs, among others. Japan has regularly conducted tactical training with U.S. B-52 strategic bombers since at least 2017, though the training is not explicitly for nuclear operations.⁵¹ Therefore, elevating the preexisting training involving nuclear-capable aircraft to explicitly nuclear training—although it would be highly politically challenging for Japan—would not only be a perfect opportunity for the two countries to signal their commitment to the alliance but also give Japan more say in U.S. nuclear operations and planning. Similarly, an arrangement involving Ohio-class SSBNs should also be considered for SNOWCAT-like naval operations. Nevertheless, an impediment to such discussions is Japan’s lack of expertise in and knowledge of nuclear-extended deterrence. As extended deterrence is a conscious choice and a serious commitment of the United States, the onus of “educating” falls on the United States, just as it did with NATO’s Nuclear Planning Group.⁵²

The Japanese experts also highlighted that Japan would most likely be the last country in Northeast Asia to gain its own nuclear weapons, citing two prerequisites for the nation to take such action: the U.S.-Japan alliance would need to be significantly weakened, and the ROK would need to have gained its own nuclear weapons first. Japan’s strong “nuclear allergy” and confidence in the alliance have played a significant role in Tokyo’s decision to rely on the U.S. nuclear umbrella rather than the nation acquiring its own nuclear weapons. However, if the United States signals that it is unwilling to fight and defend Japan from an armed attack, the effectiveness of U.S. extended deterrence would be diminished, pushing Japan to seek its own nuclear capabilities to defend itself. Similarly, if the ROK gained nuclear weapons, it would signal to Japan that the United States is unable to defend its allies through extended deterrence. That is why it is imperative for the United States to reassure Japan by building up the credibility of the alliance, which it can do through pragmatic discussions and combined exercises. However, it should be noted that the interviewed experts pointed out that Japan as a “threshold” nuclear power is enough of an implicit threat to deter potential adversaries, such as China and North Korea. Considering Japan already possesses the technology, know-how, and materials to manufacture nuclear-related technologies, both countries recognize Japan as a potential nuclear power, making them cautious in their actions.

Japanese experts also point out the importance of considering how Japan can assist the United States in more “95-2” missions based on SDF Law Article 95-2, in which the SDF protects U.S. and like-minded states’ aircraft, ships, and other assets under limited circumstances.⁵³ Though Japan does not have a commitment to defend the United States, such missions would help normalize the alliance, as it would demonstrate reciprocity. Moreover, it would signal to regional adversaries, particularly China, that both the United States and Japan are deeply committed to the alliance.

Another way Japan can contribute to the alliance is by coordinating its counterstrike capabilities with the United States. Japanese standoff missiles, which include 400 U.S.-made Tomahawks, would allow for a deep strike into China and could help close the gap between Chinese and U.S. military capabilities in the region. However, there are challenges in this area. Firstly, Japan’s counterstrike capabilities remain limited, as it will still take more than five years for them to be operational. Currently, Japan possesses limited Command, Control, Communications, Computers, Intelligence, Surveillance, and Reconnaissance (C4ISR) capabilities. Additionally, though standoff missiles are a good deterrence option, they carry an inherent risk of escalation. Thus, it is important for Japan and the United States to discuss how to carry out smooth operational coordination, as well as mitigate the risk of escalation. Nevertheless, there has been a limited willingness by Japanese policymakers to push such discussions—particularly on nuclear options—since the death of Shinzo Abe.

Japan’s main concern for U.S. extended deterrence is the credibility of U.S. commitment to the alliance obligations. British Secretary of State for Defense Denis Healey once said that it “only takes a 5 percent credibility of American retaliation to deter an attack, but it takes a 95 percent credibility to reassure the allies.”⁵⁴As this so-called Healey Theorem suggests, it does not take much work to hurt the credibility of alliance commitments, and U.S. actions over the past decade particularly made Japanese policymakers and the public question the U.S. commitment to the defense of Japan. In this regard, former President Trump’s “America First” stance and his dismissive attitudes toward its treaty allies significantly damaged Japan’s trust in U.S. alliance commitment.

Although Tokyo appreciated the Biden administration’s efforts to refocus on its allies and restore their trust in U.S. commitment, many policymakers are concerned that the U.S.-Japan alliance is not institutionalized enough to withstand “Trump 2.0”—the return of the Trump administration. It is undeniable that the alliance’s capability to defend Japan and the region is more expansive than ever, but as the stakes of security in East Asia heighten, U.S. actions are closely monitored both by its allies and adversaries, and the credibility of U.S. extended deterrence is increasingly questioned. The 2021 chaotic exit from Afghanistan and President Biden’s comments rejecting the idea of sending troops to Ukraine by implying that the reason is Russia’s status as a nuclear power greatly impacted Japan’s perception of U.S. extended deterrence. Although these events alone did not create a significant shift in Japan’s defense policy debate—especially because neither country is a U.S. treaty ally—they certainly boosted the nuclear options debate. Additionally, some senior SDF officers argued that the Biden administration’s commitment to advancing nuclear disarmament weakens the credibility of U.S. nuclear extended deterrence and amplifies Japan’s concerns. These officers also hoped that the United States would continue to deploy and utilize low-yield, submarine-launched nuclear warheads.

As it critically impacts Japan’s security discussion, U.S. extended deterrence should be discussed more openly, frequently, and deeply to prevent surprises among Japanese stakeholders. For instance, a high-ranking Air SDF officer was disappointed by and concerned about the “surprising” announcement of the U.S. Air Force’s decision to replace its fleet of F-15s at Kadena Air Base in Okinawa with a rotational force of F-22s.⁵⁵ This surprise could have been easily avoided with frequent, open discussions with Japan. Of course, an alliance is not a one-way commitment, and Tokyo needs to consider ways in which the SDF can have a larger role in supporting the U.S. forces in the Indo-Pacific with both nuclear and conventional operations. In this regard, the EDD should also become operational and discuss how Japan’s strike capabilities can complement U.S. conventional capabilities and reinforce U.S. nuclear capabilities. However, it is critical that the United States constantly and openly reconfirms its commitment to the alliance.

Policy Recommendations

Recommendation: The United States should work with Japan to find ways to facilitate more informed discussions on nuclear issues in Japan, especially in public. Even if Japan ultimately chooses to uphold its current nuclear policy, a discussion that does not rule out a nuclear-armed Japan would provide some deterrence against adversaries. Encouraging public discussion on nuclear issues may also be useful in sensitizing the Japanese public regarding the issues, which can promote a better understanding of broader extended deterrence policy options, including port calls by U.S. and like-minded countries’ nuclear-powered submarines or aircraft carriers.

Recommendation: Constant efforts to promote a better understanding of the issues relevant to extended deterrence, including nuclear, are essential to reassure Japan. The United States and Japan should jointly tackle this challenge by modernizing the existing framework of the EDD between the two governments, ensuring that the EDD is an integral part of broader alliance consultation. The recent agreement to begin consultation on how to leverage the EDD to inform bilateral operational planning, including tabletop exercises, is a step in the right direction.⁵⁶ Expanding the EDD to a multilateral framework to include the ROK and/or Australia can also be useful over the long term.

Recommendation: Bilaterally, creating a consultation forum dedicated solely to U.S. extended deterrence within the existing alliance consultation mechanism may also be beneficial. Washington and Tokyo may consider integrating aspects of the U.S.-ROK NCG after careful examination. Additionally, NATO’s SNOWCAT program could be considered as a way for Japan to provide aerial and naval support to U.S. nuclear operations using conventional weapons. Furthermore, consistent articulation of American explicit commitment to the defense of Japan from potential adversaries, including the ones with nuclear capabilities, is critical.

Recommendation: The United States should demonstrate openness to discussing U.S. nuclear planning and operation to sensitize Japanese policymakers to the concept. In particular, engaging Japanese officials in the discussion of joint operation planning that involves both conventional and nuclear capabilities will be particularly helpful to promote better understanding on the Japanese side.

Acknowledgments

This report is made possible with support and guidance from the Strategic Trends Office (SI-ST) within the U.S. Department of Defense’s Defense Threat Reduction Agency (DTRA). We are especially grateful to the interview participants and peer reviewers for their valuable insights. We would also like to thank our research interns Nicolas Velez and Chelsea Suzuko Uchida Wells for their support throughout the execution of the project, as well as Janice Fisher for professional copy editing.

Notes

1
“Japan’s Proactive Contribution to Peace,” Government of Japan, 2014, https://www.japan.go.jp/tomodachi/2014/spring-summer2014/japans_roactive_contribution_to_peace.html; “Overview of the Act on the Protection of Specially Designated Secrets (SDS),” Prime Minister’s Office of Japan, Cabinet Secretariat, 2013, https://www.kantei.go.jp/jp/topics/2013/headline/houritu_gaiyou_e.pdf; “National Security Strategy of Japan,” National Security Secretariat of Japan, December 17, 2013, https://www.cas.go.jp/jp/siryou/131217anzenhoshou/pamphlet_en.pdf; “Japan’s Legislation for Peace and Security,” Ministry of Foreign Affairs of Japan, March 2016, https://www.mofa.go.jp/files/000143304.pdf.
2
Llewelyn Hughes, “Why Japan Will Not Go Nuclear (Yet): International and Domestic Constraints on the Nuclearization of Japan,” International Security 31, no. 4 (2007): 67-96, https://www.jstor.org/stable/4137566; James J. Orr, “Hiroshima and Yuiitsu no Hibakukoku: Atomic Victimhood in the Antinuclear Peace Movement,” in The Victim as Hero: Ideologies of Peace and National Identity in Postwar Japan (Honolulu: University of Hawai’i Press, 2001), 36-70.
3
Ayako Kusunoki, “The Satō Cabinet and the Making of Japan’s Non-Nuclear Policy,” Journal of American-East Asian Relations 15 (2008): 25-50, https://www.jstor.org/stable/23613093.
4
Sayuri Romei, “Japan and the Nuclear Challenges in a New Era of Rising Tensions,” Journal of Indo-Pacific Affairs 2, no. 3 (2019): 66-84, https://www.airuniversity.af.edu/Portals/10/JIPA/journals/Volume-02_Issue-3/04-Romei.pdf.
5
Jesse Johnson, “Japan Should Consider Hosting U.S. Nuclear Weapons, Abe Says,” Japan Times, February 27, 2022, https://www.japantimes.co.jp/news/2022/02/27/national/politics-diplomacy/shinzo-abe-japan-nuclear-weapons-taiwan/; “Abe Moto-Shushō ‘Kaku Kyōuyū’ no Giron wo” 安倍元首相「核共有」の議論を [Former Prime Minister Abe: ‘We Need to Discuss Nuclear Sharing’], Sankei Shimbun, February 28, 2022, https://www.sankei.com/article/20220227-WAR5FEF3SVOYLFMCC7FOUYSOL4/#:~:text=%E3%80%8C%E6%97%A5%E6%9C%AC%E3%81%AF%E6%A0%B8%E6%8B%A1%E6%95%A3%E9%98%B2%E6%AD%A2,%E5%A4%A7%E5%88%87%E3%81%A0%E3%80%8D%E3%81%A8%E3%82%82%E8%AA%9E%E3%81%A3%E3%81%9F%E3%80%82; “‘Kaku Kyōyū’ Abe Moto Shushō ‘Genjitsu Chokushi Shi Nihon mo Giron Susumeru Hitsuyō Aru’” 「核共有」安倍元首相“現実直視し日本も議論進める必要ある” [Former Prime Minister Abe: ‘Japan Needs to Face Reality and Advance Discussions on Nuclear Sharing], Japan Broadcasting Corporation, March 3, 2022, https://www3.nhk.or.jp/news/html/20220303/k10013511741000.html.
6
Examples include the following: Nobukatsu Kanehara, “’Kaku Shearingu’ toiu Nihon ni Totte Genjitsu-Tekina Yokushi-Ryoku ga Hitsuyōna Riyū” 「核シェアリング」という日本にとって現実的な抑止力が必要な理由 [Why Japan Needs ‘Nuclear Sharing,’ A Realistic Deterrent], Gendai Bijinesu, April 2, 2022, https://gendai.media/articles/-/93938?imp=0; Katsutoshi Kawano, “Time Has Come for Japan to Discuss Nuclear Sharing,” Japan Institute for National Fundamentals, April 4, 2022, https://en.jinf.jp/weekly/archives/9355; Katsutoshi Kawano, Yukihiro Hasegawa, and Nobumasa Akiyama, “Gekiron! Nihon wa ‘Kaku Busō’ Subekinanaka… Ganzen ni Aru ‘Kyūkyoku no Ronsō’” 激論！日本は「核武装」すべきなのか…眼前にある「究極の論争」[Debate! Should Japan Go ‘Nuclear?’: The ‘Ultimate Debate’ Before Us], Gendai Bijinesu, May 3, 2022, https://gendai.media/articles/-/94915?imp=0.
7
“National Security Strategy of Japan,” National Security Secretariat of Japan, December 16, 2022, https://www.cas.go.jp/jp/siryou/221216anzenhoshou/national_security_strategy_2022_pamphlet-e.pdf.
8
“Defense Buildup Program,” Japan Ministry of Defense, December 16, 2022, https://www.mod.go.jp/j/policy/agenda/guideline/plan/pdf/program_en.pdf; “Defense Programs and Budget of Japan – Defense-Strengthening Acceleration Package – Overview of FY2022 Budget (Including FY2021 Supplementary Budget),” Japan Ministry of Defense, March 24, 2022, https://www.mod.go.jp/en/d_act/d_budget/pdf/20220420.pdf.
9
See, for example, “Joint Statement of the United States and Japan,” The White House, January 13, 2023, https://www.whitehouse.gov/briefing-room/statements-releases/2023/01/13/joint-statement-of-the-united-states-and-japan/.
10
“Remarks by President Biden Announcing Response to Russian Actions in Ukraine,” The White House, February 22, 2022, https://www.whitehouse.gov/briefing-room/speeches-remarks/2022/02/22/remarks-by-president-biden-announcing-response-to-russian-actions-in-ukraine/; Aaron Blake, “Why Biden and the White House Keep Talking About World War III,” Washington Post, March 17, 2022, https://www.washingtonpost.com/politics/2022/03/17/why-biden-white-house-keep-talking-about-world-war-iii/; Zack Beauchamp, “Why the US Won’t Send Troops to Ukraine,” Vox, February 25, 2022, https://www.vox.com/policy-and-politics/2022/2/25/22949351/ukraine-russia-us-troops-no-fly-zone-nuclear-weapons.
11
“Japan-U.S. Extended Deterrence Dialogue,” United States Department of State, November 16, 2022, https://www.state.gov/japan-u-s-extended-deterrence-dialogue-2/; Nobuyasu Abe, “The Biden Nuclear Posture Review and Its Implications for US Asia-Pacific Allies,” Journal for Peace and Nuclear Disarmament 4, no. 2 (2021): 235-250, https://doi.org/10.1080/25751654.2021.2015919; “Japan-U.S. Security Arrangements: Japan-U.S. Security Consultative Committee (2+2),” Ministry of Foreign Affairs of Japan, January 11, 2023, https://www.mofa.go.jp/region/n-america/us/security/scc/index.html.
12
See, for example, “Alert! Abe’s Remarks Are Unlocking Japan’s Militarism: Global Times Editorial,” Global Times, February 28, 2022, https://www.globaltimes.cn/page/202202/1253381.shtml.
13
Paiyao Xia and Liang Jun, “China Urges Japan to Act Prudently on Taiwan Question,” People’s Daily online, March 1, 2022, http://en.people.cn/n3/2022/0301/c90000-9964034.html; Paiyao Xia and Liang Jun, “China Urges Japan to Be Cautious Concerning Nuclear Sharing Talks: Spokesperson,” People’s Daily online, March 15, 2022, http://en.people.cn/n3/2022/0315/c90000-9971142.html.
14
Hans M. Kristensen, Matt Korda, and Eliana Johns, “Chinese Nuclear Weapons, 2023,” Bulletin of the Atomic Scientists 79, no. 2 (2023): 108-133, https://doi.org/10.1080/00963402.2023.2178713.
15
See, for example, Mike Mochizuki, “Three Reasons Why Japan Will Likely Continue to Reject Nuclear Weapons,” Washington Post, November 6, 2017, https://www.washingtonpost.com/news/monkey-cage/wp/2017/11/06/japan-is-likely-to-retain-its-non-nuclear-principles-heres-why/; Sayuri Romei, “The Legacy of Shinzo Abe: A Japan Divided About Nuclear Weapons,” Bulletin of the Atomic Scientists, August 24, 2022, https://thebulletin.org/2022/08/the-legacy-of-shinzo-abe-a-japan-divided-about-nuclear-weapons/; Mohammad Abu Ghazleh, “Five Reasons Why Japan Will Unlikely Go Nuclear,” Jordan Times, May 14, 2022, https://jordantimes.com/opinion/mohammad-abu-ghazleh/five-reasons-why-japan-will-unlikely-go-nuclear.
16
Examples include the following: Brad Roberts, The Case for U.S. Nuclear Weapons in the 21st Century, trans. Masashi Murano, Shinichi Hirao, Sayuri Romei, and Yuuri Sano (Tokyo: Keisō Shobō, 2022); Yoko Iwama, Hiromu Arakaki, Itsuki Kurashina, Hiroyuki Kobayashi, Chihaya Kokubo, Tsuyoshi Goroku, Shuichi Kawashima, and Keitaro Ushirogata, Kaku Kyōyū no Genjitsu: NATO no Keiken to Nihon 核共有の現実：NATOの経験と日本 [The Reality of Nuclear Sharing: The Case for NATO and the Implications for Japan], ed. Yoko Iwama (Tokyo: Shinzansha, 2023); Sho Tada, Kakuheiki Nyūmon 核兵器入門 [An Introduction to Nuclear Weapons] (Tokyo: Seikaisha, 2023).
17
“2006-nen 10-gatsu Chōsa” 2006年10月調査 [Survey, October 2006], TV Asahi, October 30, 2006, https://www.tv-asahi.co.jp/hst_archive/poll/200610/index.html.
18
“Jimin, Ishin Shiji-sō ‘Kaku Kyōyū no Giron Motomeru Keikō” 自民、維新支持層「核共有」の議論求める傾向 [LDP and Ishin Supporters Seek ‘Nuclear Sharing’ Discussion], Sankei Shimbun,
March 21, 2022, https://www.sankei.com/article/20220321-HCS4IPTQKFPJBDV44EXPKSBZTE/.
19
“Ukuraina Shinkō Meguri Nihon no Anzen Hoshō ‘Fuan’ 87% Mainichi Shimbun Yoron Chōsa” ウクライナ侵攻巡り日本の安全保障「不安」87%　毎日新聞世論調査 [87% of Respondents Are ‘Concerned” About Japan’s Security in the Wake of the Invasion of Ukraine, Mainich Survey Finds], Mainichi Shimbun, March 19, 2022, https://mainichi.jp/articles/20220319/k00/00m/040/267000c.
20
“The CNS North Korea Missile Test Database,” James Martin Center for Nonproliferation Studies, last modified April 28, 2023, https://www.nti.org/analysis/articles/cns-north-korea-missile-test-database/; “North Korean Missile Launches & Nuclear Tests: 1984-Present,” Missile Threat, Center for Strategic and International Studies, last modified April 25, 2023, https://missilethreat.csis.org/north-korea-missile-launches-1984-present/; David E. Sanger, “Missile Is Tested by North Koreans,” New York Times, June 13, 1993, https://www.nytimes.com/1993/06/13/world/missile-is-tested-by-north-koreans.html; Jesse Johnson, “North Korean Missile Prompts Japan to Issue Brief Evacuation Warning,” Japan Times, April 13, 2023, https://www.japantimes.co.jp/news/2023/04/13/national/north-korea-missile-hokkaido-shelter/.
21
Shion Higashimura, “Kitachōsen ‘Misairu Jikken’ ni Nihon ga Nare Kiru Osoroshisa” 北朝鮮｢ミサイル実験｣に日本が慣れきる恐ろしさ [The Horror of Japan Becoming Accustomed to North Korean Missile Tests], Toyo Keizai online, November 19, 2022, https://toyokeizai.net/articles/-/633882; “Koike Chiji ‘Kitachōsen no Misairu Hassha ni Wareware wa Nare Sugite Iru’ to Kikikan J Arāto dewa Seifu ni Yōbō” 小池知事「北朝鮮のミサイル発射に我々は慣れすぎている」と危機感　Ｊアラートでは政府に要望 [Governor Koike: ‘We Are Too Used to North Korea’s Missile Launches,’ Sharing Sense of Concern, and Gave Requests to the Government on J-ALERT], Nikkan Sports,
April 14, 2023, https://www.nikkansports.com/general/nikkan/news/202304140001089.html.
22
Vann H. Van Diepen, “North Korea’s New HS-18 Makes a Solid but Incremental Contribution to the ICBM Force,” 38 North, Stimson Center, April 20, 2023, https://www.38north.org/2023/04/north-koreas-new-hs-18-makes-a-solid-but-incremental-contribution-to-the-icbm-force/.
23
Pablo Robles and Choe Sang-Hun, “Why North Korea’s Latest Nuclear Claims Are Raising Alarms,” New York Times, June 2, 2023, https://www.nytimes.com/interactive/2023/06/02/world/asia/north-korea-nuclear.html.
24
Robles and Sang-Hun, “Why North Korea’s Latest Nuclear Claims Are Raising Alarms.”
25
“National Security Strategy of Japan,” 2022.
26
“Gaikō ni Kansuru Yoronchōsa” 外交に関する世論調査 [Public Opinion Polls on Diplomacy], Cabinet Office, Japan, November 25, 2013, https://survey.gov-online.go.jp/h25/h25-gaiko/index.html; “Gaikō ni Kansuru Yoronchōsa” 外交に関する世論調査 [Public Opinion Polls on Diplomacy], Cabinet Office, Government of Japan, February 13, 2023, https://survey.gov-online.go.jp/r04/r04-gaiko/gairyaku.pdf.
27
“Taiwan Contingency Also One for Japan, Japan-U.S. Alliance: Ex-Japan PM Abe,” Kyodo News, December 1, 2021, https://english.kyodonews.net/news/2021/12/b38433927c1e-taiwan-contingency-also-one-for-japan-japan-us-alliance-abe.html.
28
James L. Schoff and David Song, “Five Things to Know About Japan’s Possible Acquisition of Strike Capability,” Carnegie Endowment for International Peace, August 14, 2017, https://carnegieendowment.org/2017/08/14/five-things-to-know-about-japan-s-possible-acquisition-of-strike-capability-pub-72710.
29
Joseph P. Harahan, “Resolving Ukraine’s Nuclear Inheritance,” in With Courage and Persistence: Eliminating and Securing Weapons of Mass Destruction with the Nunn-Lugar Cooperative Threat Reduction Programs (Fort Belvoir, VA: Defense Threat Reduction Agency, 2014): 101-134.
30
See, for example, Kunio Orita, “Kaku Hōki kara Hajimatta Ukuraina Kiki, Chikara Naki Gaikō no Genjitsu” 核放棄から始まったウクライナ危機、力なき外交の現実 [The Ukraine Crisis That Began with the Abandonment of Nuclear Weapons: The Reality of Diplomacy without Power], JBpress, February 22, 2022, https://jbpress.ismedia.jp/articles/-/68942; Seiichi Kato, “Kaku wo Hōki Shita Ukuraina no Higeki” 核を放棄したウクライナの悲劇 [The Tragedy of Ukraine Abandoning Nuclear Weapons], Japan Forum on International Relations, February 24, 2022, https://www.jfir.or.jp/cgi/m-bbs/index.php?no=5268; Ellie Cook, “Bill Clinton: My Nuke Deal to Blame for Russia’s Invasion of Ukraine,” Newsweek, April 5, 2023, https://www.newsweek.com/bill-clinton-ukraine-war-russia-nuclear-weapons-deal-vladimir-putin-1792682#:~:text=Bill%20Clinton%3A%20My%20Nuke%20Deal%20To%20Blame%20for%20Russia’s%20Invasion%20of%20Ukraine,-Apr%2005%2C%202023&text=Former%20U.S.%20President%20Bill%20Clinton,aftermath%20of%20the%20Cold%20War; John Ullyot and Thomas D. Grant, “The Lesson of Budapest? Hold On to Your Nuclear Weapons,” Wall Street Journal, March 2, 2022, https://www.wsj.com/articles/the-lesson-of-budapest-hold-on-to-your-nukes-ukraine-russia-invasion-nuclear-weapons-proliferation-11646257487.
31
“Keynote Address by Prime Minister KISHIDA Fumio at the IISS Shangri-La Dialogue,” Prime Minister’s Office of Japan, June 10, 2022, https://japan.kantei.go.jp/101_kishida/statement/202206/_00002.html.
32
“National Security Strategy of Japan,” 2022.
33
“Seisaku Teigen: Ishin Hassaku 2022” 政策提言：維新八策 [Policy Recommendations: Ishin Hassaku 2022], Japan Innovation Party, June 16, 2022, https://o-ishin.jp/sangiin2022/ishinhassaku2022.pdf; “Chikujō Kaisetsu: Ishin Hassaku 2022 Manifesuto” 逐条解説：維新八策２０２２マニフェスト [Article-by-Article Explanation: Ishin Hassaku 2022 Manifestos], Japan Innovation Party, June 2022, https://o-ishin.jp/policy/pdf/chikujokaishaku.pdf; Tim Kelly and Kaori Kaneko, “Japanese Populist Calls for Say over Any Use of U.S. Nuclear Bombs,” Reuters, June 29, 2023, https://www.reuters.com/world/asia-pacific/japanese-populist-calls-say-over-any-use-us-nuclear-bombs-2023-06-29/.
34
Gregory Kulacki, Japan and America’s Nuclear Posture: An Update (Cambridge, MA: Union of Concerned Scientists, 2013), https://www.ucsusa.org/sites/default/files/2019-09/Japan-US-Nuclear-Posture-Update.pdf.
35
“NATO’s Nuclear Sharing Arrangements,” North Atlantic Treaty Organization, February 2022, https://www.nato.int/nato_static_fl2014/assets/pdf/2022/2/pdf/220204-factsheet-nuclear-sharing-arrange.pdf.
36
Hans M. Kristensen and Robert S. Norris, “The B61 Family of Nuclear Bombs,” Bulletin of the Atomic Scientists 70, no. 3 (2014): 79-84, https://doi.org/10.1177/0096340214531546; “NATO’s Nuclear Deterrence Policy and Forces,” North Atlantic Treaty Organization, last modified November 30, 2023, https://www.nato.int/cps/en/natohq/topics_50068.htm.
37
“2022 National Defense Strategy of the United States of America: Including the 2022 Nuclear Posture Review and the 2022 Missile Defense Review,” U.S. Department of Defense, October 27, 2022, https://media.defense.gov/2022/Oct/27/2003103845/-1/-1/1/2022-NATIONAL-DEFENSE-STRATEGY-NPR-MDR.PDF; Paul K. Kerr and Mary Beth D. Nikitin, “Nuclear-Armed Sea-Launched Cruise Missile (SLCM-N),” Congressional Research Service, last updated on December 16, 2022, https://crsreports.congress.gov/product/pdf/IF/IF12084.
38
“Treaty on the Non-Proliferation of Nuclear Weapons,” opened for signature July 1, 1968, United Nations Treaty Series: Treaties and International Agreements Registered or Field and Recorded with the Secretariat of the United Nations 729, no. 10485 (1974): 161-299, https://treaties.un.org/doc/Publication/UNTS/Volume%20729/v729.pdf.
39
Masayuki Karasudani, “A Clash of Two Nuclear Discourses and ‘Nuclear Allergy’: An Examination of the Debate on the Port Calls by Nuclear-Powered Submarines in 1960s Japan,” Journal of Law, Politics, and Sociology 89, no. 2 (2016): 189-211, https://koara.lib.keio.ac.jp/xoonips/modules/xoonips/download.php/AN00224504-20160228-0189.pdf?file_id=113975.
40
“Kishida Says Japan Won’t Seek Nuclear Sharing with U.S,” Kyodo News, February 28, 2022, https://english.kyodonews.net/news/2022/02/523fce75f78a-kishida-says-japan-wont-seek-nuclear-sharing-with-us.html.
41
See, for example, “G7 Leaders’ Hiroshima Vision on Nuclear Disarmament,” G7 Hiroshima Summit, May 19, 2023, https://www.g7hiroshima.go.jp/documents/pdf/230520-01_g7_en.pdf.
42
Claire Mills, “AUKUS Submarine (SSN-A) Programme,” House of Commons Library, United Kingdom Parliament, last modified November 22, 2023, https://researchbriefings.files.parliament.uk/documents/CBP-9843/CBP-9843.pdf.
43
Jesse Johnson, “Kishida Calls Idea of Japan Sharing Nukes with U.S. ‘Unacceptable’,” Japan Times, February 28, 2022, https://www.japantimes.co.jp/news/2022/02/28/national/politics-diplomacy/kishida-nuclear-sharing-abe/; “Shushō, Kaku Kyōyū ‘Seifu de Giron Suru Kangaenai’” 首相、核共有「政府で議論する考えない」 [Prime Minister: Nuclear Sharing “Is Not Something We Intend to Discuss in the Government”], Nihon Keizai Shimbun, March 2, 2022, https://www.nikkei.com/article/DGXZQOUA022AI0S2A300C2000000/; Atomic Energy Basic Act, Act No. 186 of 1955, as amended through Act No. 65 of 2020, promulgated on July 3, 1955, official Gazette (Kanpō), Extra Edition No. 93, July 5, 1955, 1-7.
44
“Japan Nuclear Overview,” Nuclear Threat Initiative, October 11, 2018, https://www.nti.org/analysis/articles/japan-nuclear/.
45
National Diet of Japan, House of Representatives, Committee on Foreign Affairs, 第百七十四回国会衆議院外務委員会議録第五号 [Minutes of Proceedings No. 5 from the Committee on Foreign Affairs, House of Representatives, 174th National
Diet], 174th National Diet, 2010, https://kokkai.ndl.go.jp/#/detailPDF?minId=117403968X00520100317&page=1&spkNum=0&current=1.
46
Toru Kawaguchi, “1975-nen no Hikaku Kōbe Hōshiki wo Meguru Chūō Chihō Kankei” 1975年の非核神戸方式を巡る中央地方関係 [Central-Local Government Relations over the Non-Nuclear Kobe Method in 1975], Waseda Journal of Social Sciences 16 (2010): 43-53, https://waseda.repo.nii.ac.jp/?action=repository_action_common_download&item_id=16144&item_no=1&attribute_id=162&file_no=1.
47
Hanshin Daishinsai no Ippō ni Kizuita no wa Keibiin Datta Beigun no Kyūen-An ni ‘Kakuheiki wa?’ to Nanshoku ga Shimesareta” 阪神大震災の一報に気づいたのは警備員だった　米軍の救援案に「核兵器は？」と難色が示された [A Security Guard Was the First to Notice the News of the Great Hanshin Earthquake. The U.S. Military’s Rescue Plan Was Met with Resistance], Sankei Shimbun, March 7,
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