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Amid North Korea’s apparent progress in its nuclear weapons program and China’s military build-up, including the modernization of its nuclear arsenal, experts and officials in East Asia, particularly those in Japan and the Republic of Korea, are nowadays discussing more frequently the issues related to extended deterrence, not least its nuclear elements called extended nuclear deterrence or “nuclear umbrella.”² While nuclear deterrence had always been one of the pillars of the US security commitment to the region, the United States and its allies in East Asia did not have to rely much on it for a long time as, unlike the European theater during the Cold War, the conventional balance has been consistently in favor of the US side. The situation is changing now, and the conventional balance is shifting more toward China’s favor, though the United States and its allies still maintain a qualitative edge vis-à-vis China. This, at least in theory, suggests that, in the region, they might have to rely more on nuclear deterrence than in the past, in spite of the fact that Obama has been championing the opposite since his speech in Prague in 2009.³

Experts and officials in East Asia are increasingly looking at other examples of US extended nuclear deterrence, not least the North Atlantic Treaty Organization (NATO). The heightened interest in NATO’s nuclear-sharing mechanism, including the deployment of US tactical nuclear weapons on European soil and the Nuclear Planning Group (NPG) as a venue to discuss nuclear issues in the alliance, shows a great deal about how East Asian debates are evolving. The “NATO model” of managing extended nuclear deterrence is being discussed as what the US allies in East Asia might want to adopt. The NATO model, at least for some, appears to be more effective in terms of maintaining and strengthening the credibility of US extended deterrence in an era of increasing security threats and challenges exemplified by North Korea’s missile and nuclear development and China’s military build-up.

It has become popular to compare Europe and East Asia in the Western nuclear policy and deterrence community, resulting in an increasing number of comparative works on deterrence.⁴ It is true that there is a clear and substantial difference between the NATO model and the practices in East Asia—mainly the US-Japan and US-Korea alliances—or the East Asia model. The former is based on nuclear-sharing and the forward deployment of US nuclear weapons, whereas the latter lacks such features, which this article generally shares. However, it is a matter of degree, and this article argues the need to move beyond such a dichotomy, so that East Asia and Europe could learn from each other’s practices and experience.

A little ironically in Europe, more experts and officials are getting interested in an East Asia model of extended deterrence, which, unlike NATO’s case, does not involve the forward deployment of US nuclear weapons among other differences. What stimulates this interest is obviously the ongoing debates in Europe on the future of US tactical nuclear weapons. For those who argue for the withdrawal of such weapons, the East Asian model looks promising, as it appears to be demonstrating that the credibility of US extended deterrence can still be maintained without the forward deployment of nuclear weapons. Yet others, who support the continued deployment of tactical nuclear weapons in Europe, regard the East Asian model in exactly the opposite way. They argue that because of the lack of physical element that underwrites the US nuclear commitment, US allies in East Asia are increasingly weary of the credibility of extended deterrence and beginning to look at the NATO model as a way forward. They conclude, therefore, it is not a choice NATO should take for its future.

The increasing mutual interest between East Asia and Europe, in itself, might be something that should be welcomed given a long history of little interaction between the two regions regarding the issues of deterrence and nuclear weapons. However, so as to avoid superficial or misguided discussions, there needs to be a solid understanding of the similarities and differences of the European and East Asian debates on extended nuclear deterrence, the role of nuclear weapons, and wider regional strategic environments in which the two regions are situated.Only through having such an intellectual foundation, generic issues that both Europe and East Asia need to address could be explored.

This article first reviews some of the significant characteristics of both the NATO and East Asian models of extended nuclear deterrence. It then examines common challenges that both Europe and East Asia need to address today: the meaning of the forward deployment of nuclear weapons; the nature of nuclear consultations; and the means to counter nuclear saber-rattling and fears of limited use of nuclear weapons by adversaries.

The NATO Model

NATO identifies itself as a “nuclear alliance,” though there is no official definition of what it means. At a minimum, it means that nuclear weapons play a role in the alliance’s deterrence and defense posture. Indeed, nuclear weapons constitute one of the most important components in NATO’s “appropriate mix” of tools for deterrence and defense, demonstrating that NATO allies are covered by the US nuclear commitment. However, if that is all the nuclear alliance means, it would not look special: Washington has repeatedly made explicit nuclear commitments to Japan and South Korea as well. Rather, what makes the NATO model special is its notion of the “broadest possible participation of Allies in collective defense planning on nuclear roles, in peacetime basing of nuclear forces, and in command, control and consultation arrangements.”⁵ No other US allies are involved in the “broadest possible participation” in such a wide range of nuclear activities with the United States.

While never officially acknowledged, it is widely believed that five NATO countries in Europe—Belgium, Germany, Italy, the Netherlands, and Turkey—host around 180 US tactical (non-strategic) nuclear weapons—B-61 gravity bombs—on their soil today.⁶ Those warheads are supposed to be employed by dual-capable aircraft (DCA) of those European countries as well as the United States under the alliance’s nuclear-sharing arrangements. For this mechanism to continue, European DCA fleets need to be certified regularly by the United States, which involves sharing technical information and expertise on nuclear weapons, as the highly exclusive “nuclear club” within the alliance.

Beyond those physical elements, another feature of NATO as a nuclear alliance is that it has a permanent venue to conduct consultations on nuclear issues. Since it was established in 1967, the NPG has mainly dealt with the use of non-strategic nuclear weapons, particularly those under the alliance’s nuclear-sharing arrangements. Though it was never directly in charge of US strategic weapons, the NPG and its subordinate body, the High-Level Group (HLG), have served as a prime venue to discuss a range of nuclear issues within the alliance. From the beginning, nuclear consultation exemplified by the NPG has been intended to be a tool to reassure non-nuclear allies, most notably West Germany during the Cold War.⁷

Arguably, the most important principle underpinning different elements of nuclear sharing and nuclear consultation is the idea of “risk- and responsibility-sharing” among the allies.⁸ Particularly during the Cold War, those who were hosting US nuclear weapons were believed more likely to be attacked by the Soviet Union, thus shouldering the risk. In return for this, nations wanted to have a say—as an exercise of responsibility. Europeans wanted to make the deterrence relationship reciprocal to avoid complete dependence on the United States. Though recognizing that the nuclear sharing arrangements in NATO represented only a tiny part in the overall nuclear deterrence posture that depended heavily on US strategic weapons, it was important as a matter of principle to maintain the mechanism to ensure the “broadest possible participation” of allies in NATO’s nuclear business, which continues to this day, to ensure the elements of reciprocity and the mutual nature of the alliance’s deterrence posture.⁹

NATO has experienced a series of crises involving the credibility of US extended deterrence. Nevertheless, the fact that NATO enjoys all possible measures—both consultative and physical means—regarding extended nuclear deterrence, something other US allies lack, makes the NATO model unique and attracts the attention of those who look for ways to strengthen the US extended nuclear deterrence commitment.

The East Asian Model

In contrast to the NATO model, which features the forward deployment of US non-strategic nuclear weapons in Europe, the East Asian model is usually understood to be the one that lacks physical elements. As far as today’s US-Japan and US-South Korea alliances are concerned, this is correct. Neither ally hosts US nuclear weapons on its soil. However, extended deterrence in East Asia also used to be characterized by the forward deployment of US nuclear weapons. It began to deploy nuclear weapons in Okinawa, which was at the time under US administration, as early as the mid-1950s, immediately following the introduction of US nuclear weapons into West Germany. The deployment continued until Okinawa’s reversion to Japan in the early 1970s. Furthermore, various US bases in mainland Japan hosted non-nuclear components of nuclear weapon systems such as missiles and aircraft. In a contingency, nuclear warheads were supposed to be transported to Japan and fitted to these deployed non-nuclear components. It was a compromise between the US military’s unsuccessful attempt to introduce nuclear weapons to mainland Japan and Japan’s strong opposition to host nuclear weapons on its own soil. Declassified US documents also show that the US military was eager to introduce a NATO-style nuclear sharing mechanism to Japan in the 1960s.¹⁰

Therefore, in the US-Japan alliance as well, extended deterrence until the 1970s contained an element of the physical existence of forward-deployed nuclear weapons. Nevertheless, it is another thing whether or to what extent Japanese political leaders regarded such a reality and practice as constituting one of the pillars of extended deterrence by the United States. At least, there is not much evidence that successive Japanese governments consciously shared the nuclear burden—exercised “nuclear burden-sharing” by taking risks—for the purpose of maintaining the credibility of the US extended deterrence to Japan.¹¹

In contrast, the United States had a clear idea of what it wanted regarding nuclear weapons vis-à-vis Japan as part of its global strategy and extended deterrence. It needed to secure, first, the right of transit of nuclear weapons or “nuclear visiting”—port calls in Japan by US navy vessels carrying nuclear weapons; and second, the right to re-introduce nuclear weapons to Okinawa in time of dire emergency. After much hesitation and lengthy negotiations, Japan and the United States concluded a series of secret agreements and reached a common understanding on those matters. Though Tokyo had long denied any secret agreement in this regard, a government led by the Democratic Party of Japan in 2010 revealed the existence of some explicit and implicit secret agreements and understandings between the two reached during the Cold War.¹² The fact that Japan allowed nuclear-armed US vessels to visit Japanese ports and was prepared to let the US re-introduce nuclear weapons in an emergency is thought to have strengthened the deterrence posture of the US-Japan alliance.

After the withdrawal of all the US nuclear weapons from Okinawa in the early 1970s, the ultimate guarantee of Japan’s defense has been US strategic weapons as well as Japanese and US conventional forces. Mainly because of the fact that the conventional balance vis-à-vis the Soviet Union and China has been consistently in favor of the US-Japan side, Japan’s need to depend on the nuclear element of extended deterrence has remained low. Also, there has been a high level of “nuclear allergy” in Japan, making it difficult for many Japanese to address nuclear weapon issues in concrete and militarily logical terms. As James Schoff argues, “how deterrence worked mattered little” to Japan and “Tokyo seldom concerned itself with details” about extended deterrence.¹³ Elbridge Colby is blunter, describing Japan’s attitude as “see no evil, hear no evil.”¹⁴ In such a situation, not much serious debate took place on how Japan can be involved in US nuclear doctrine and planning. The situation began to change only after North Korea’s accelerating nuclear development and the changing conventional balance due to China’s military build-up.

The Korean case has a longer history of direct deployment of US non-strategic nuclear weapons. From 1958 to 1991, the United States maintained a substantial number of nuclear weapons there. President George H.W. Bush decided to withdraw all of them as part of the Presidential Nuclear Initiatives (PNIs) in 1991. However, the most significant difference between the Korean and NATO cases is that the South Korean authorities were never allowed to get involved in the planning and employment of nuclear weapons including those deployed in South Korea. They had no say on the use of those weapons by the Americans. This was amply demonstrated by the fact that the US decision to withdraw all the nuclear weapons from South Korea was made almost unilaterally.¹⁵

In addition to hosting US nuclear weapons, South Korea, particularly in the 1970s under President Park Chung-hee, secretly sought to develop its own nuclear weapons. The idea of developing endogenous nuclear weapons came essentially from Seoul’s anxieties about US abandonment.¹⁶ Washington’s successive efforts to strengthen the credibility of extended deterrence to Korea have proved to be effective in preventing Seoul from trying to acquire its own nuclear weapons again. However, what is different from Japan is that the public approval rating for the idea of developing Korea’s own nuclear weapons has been consistently high—around two-thirds support it—which is why, it is often argued that “if a new nuclear-armed state were to emerge in Northeast Asia, it would most likely be the Republic of Korea.”¹⁷

Japan and South Korea have been making more efforts to maintain and enhance the credibility of US extended deterrence, facing what they perceive as a deteriorating security environment, most notably due to China and North Korea.

Common to the two allies is to start and strengthen consultations with Washington on nuclear deterrence and extended deterrence.Such consultations on nuclear issues with Japan and South Korea among other allies and partners in 2009 began in the context of a new US Nuclear Posture Review (NPR), which was released in April 2010. Following the initial success of such consultations, the United States and Japan established the “Extended Deterrence Dialogue (EDD)” and the United States and South Korea the “Extended Deterrence Policy Committee (EDPC),” both in 2010.¹⁸ The US-Korean one was renamed in 2015 the “Deterrence Strategy Committee (DSC).”¹⁹

These dialogue frameworks have quickly become a premier venue to discuss extended deterrence issues between the allies and an “assurance tool” by fostering a “sense of inclusion” for Japanese and Koreans. The dialogues now include table top exercises based on high-intensity contingencies and onsite visits to US nuclear facilities.²⁰ The Obama administration has shown greater willingness to institutionalize and expand these dialogues, indicating that the United States accepts the fact that it is not in the US interest to leave allies ill-informed about US intentions (policies) and capabilities and questioning the US commitment. Keeping the allies well informed and updated is now seen as one of the surest ways to reassure them, i.e., “educating” the allies from the US point of view.

Spectrum of Nuclear Burden-Sharing

One way to compare the NATO and East Asian models of extended nuclear deterrence, based on what has been discussed above, is to put different elements at various levels within an integrated spectrum (or hierarchy) of what could be called nuclear burden-sharing—NATO’s model of nuclear-sharing is one form of nuclear burden-sharing, but the latter is a much broader concept. On the top of this spectrum sit the United Kingdom and France as independent nuclear powers, though their contributions to NATO’s deterrence and defense posture vary because whereas the UK nuclear deterrent is dedicated to the alliance, the French one is not integrated into the NATO structure. What comes next is the main physical element of NATO’s nuclear sharing—operating DCA and hosting US nuclear weapons, constituting the clearest examples of nuclear burden-sharing. However, there are other means of shouldering nuclear burdens, including non-DCA (and non-host) NATO countries’ participation in nuclear support missions including refuelling, reconnaissance, and escort, something in which Poland now takes part.²¹ That Japan hosted non-nuclear components of nuclear weapon systems until the 1970s, mentioned above, can also be put in this context. Similarly, US intelligence and command and control-related facilities in Australia should also be seen as a direct contribution to the global nuclear deterrence posture, the value of which was particularly high during the Cold War.²²

While accepting visits of US vessels carrying nuclear weapons may not seem to be a substantial form of nuclear burden-sharing, it was significant enough that New Zealand’s decision to reject such visits in the mid-1980s caused the Reagan administration to withdraw a security commitment from the island nation.²³ While what the US navy wanted in New Zealand was mainly to secure a place for the crew to take a rest—therefore not for military operational purposes—this incident has demonstrated the significance placed on “nuclear visiting.” As has been discussed above, Tokyo during the Cold War tacitly allowed US vessels carrying nuclear weapons to call on ports in Japan.

Table 1: Spectrum (Hierarchy) of Nuclear Burden-Sharing

The relative significance of each measure keeps changing contingent on the evolving international security environment and US interests and concerns. For example, it can be argued that Japan’s ballistic missle defense capability matters more than participation in NATO’s nuclear support mission in military terms. There are diverse forms of nuclear burden-sharing; one does not always need to host US nuclear weapons.

Common Challenges Facing Europe and East Asia

Despite different contexts, security situations, and histories, Europe and East Asia are now facing an increasingly common challenge regarding how to maintain the credibility of US extended nuclear deterrence. Three major challenges are discussed below.

Challenge 1: Making sense of forward deployment
The question to what extent the forward deployment of tactical (non-strategic) nuclear weapons on allies’ soil is necessary for the purpose of maintaining the credibility of US commitment remains controversial. Put simply, it is a question of how much visibility matters to the credibility of the US commitment.²⁴ One of the most important advantages of forward-deployed nuclear weapons is that those are visible. We may still have an instinct of “seeing is believing.” That was why the US decision to retire nuclear-tipped Tomahawk cruise missiles (TLAM/N) became controversial in the run-up to the 2010 NPR.²⁵ While TLAM/N had not been deployed to Asia since the 1990s, it was seen as one of the most deployable of US nuclear weapons.

Although the debates on the pros and cons of the retirement of TLAM/N now look outdated, one question that remains not fully answered is why, on the one hand, TLAM/N was judged to be substitutable by other means like the deployment of bombers and fighters in contingencies in the Asia-Pacific theater, but on the other hand, the forward deployment of US tactical nuclear weapons on European soil could not be substituted by other means. It is, indeed, easy to point to different contexts and histories, and institutional inertia certainly plays a role when it comes to NATO’s nuclear posture. While fully recognizing the uniqueness of NATO’s arrangements, the United States would still need to do a better job explaining why there is such a difference in its position on the “substitutability” of forward deployment of nuclear weapons, i.e., it needs to better legitimize the continuing deployment of tactical nuclear weapons in Europe in a more generic and coherent way beyond simply relying on the uniqueness of NATO.²⁶ Such an exercise would sharpen our understanding on when and where forward deployment of nuclear weapons is still needed and desirable and when and where it is not.

Challenge 2: Strengthening consultations
The role of consultations on nuclear-related issues is likely to increase in both NATO and East Asia. As for NATO, despite the fact that any talk of withdrawing US non-strategic nuclear weapons from Europe has all but disappeared in the wake of the Ukraine crisis, the need for DCA states to replace their aging fleets remains, and the time for decision is approaching. It will not be easy for countries to decide to replace DCA; NATO will have to prepare a “Plan B” in case European allies lose DCA. It will not be an end to NATO’s status as a nuclear alliance.

There have already been various ideas put forward by experts on how NATO could maintain elements of nuclear-sharing, if not all the features that exist today, without the physical presence of US nuclear weapons on allied territory or without European DCA capability,²⁷ including keeping selected nuclear storage facilities certified for a possible return of nuclear weapons when needed, maintaining European DCA capability at the NATO level rather than at the national level, and sending allied officers to the United States, and letting them be involved in US nuclear missions. But if US nuclear weapons in Europe and/or European DCA capabilities were to be lost, the basic nature of NATO’s nuclear-sharing or, more broadly, the mechanism of risk- and responsibility-sharing, would have to change substantially.

That is exactly why NATO needs to start thinking about how it can continue nuclear consultations without relying on the physical elements of nuclear-sharing—or how it can prevent the NPG from becoming nothing more than a “tea ceremony.”²⁸ In such a situation, challenges for NATO allies, on the one hand, and Japan and South Korea, on the other, would look more similar. Japan and South Korea are latecomers in this regard, and there are certainly many lessons that the two need to learn from NATO’s experience of nuclear consultations—both successes and limitations; however, the interaction between NATO and US East Asian allies could, in the coming years, become more mutual rather than just a one-way street, where only Asians learn from the other.

In the final analysis, the biggest challenge for US allies in both Europe and Asia is how they can keep Americans serious about such consultations. The good news is that under the Obama administration the United States seems to understand more than ever before that keeping allies well informed and updated is probably the most effective way to reassure allies about the credibility of US extended deterrence. However, the undeniable fact remains that everything depends on US willingness, which cannot be taken for granted. Therefore, allies in Europe and East Asia need to keep showing to the Americans the merits of maintaining nuclear consultations with their allies, including through shouldering more burden and responsibilities.

Challenge 3: Countering nuclear saber-rattling and limited use
The newest nuclear-related challenge that confronts both Europe and Asia concerns nuclear saber-rattling by Russia and related fear of the limited use of nuclear weapons by adversaries—mainly Russia, but to a lesser extent China as well. In the wake of the Ukraine crisis, Vladimir Putin and his top aides have repeatedly reminded the world that Russia is still a country possessing one of the world’s largest nuclear arsenals and intimidated neighbors by showing Russia’s willingness and preparedness to use nuclear weapons even in regional conflict. Russia has conducted a series of military exercises involving simulated nuclear attacks.²⁹ Such actions have largely been targeted against NATO, but East Asia cannot be immune from Russia’s stepped-up nuclear saber-rattling in the light of its increasingly assertive actions in East Asia. There are growing calls to adapt NATO’s nuclear posture, starting with declaratory policy to counter Russia’s moves, which is also a matter of concern for Japan and South Korea. There needs to be consultations between NATO and US allies in Asia to ensure unity and synergy.

Related to this is the West’s increasing concern about the possible use of nuclear weapons by its adversaries, most notably Russia. While it is not yet clear whether Moscow has actually lowered its nuclear threshold, there are increasing impressions that Russia might be more willing to use nuclear weapons now than in the past, raising concerns in the West, most notably among experts in the US.³⁰ On the one hand, it can be argued that Russia’s stepped-up nuclear intimidation is mostly rhetorical in nature and, therefore, should not be taken at face value, because raising fears in the West is exactly what Moscow intends to achieve. On the other hand, particularly from the viewpoint of US allies, the fact that Americans are increasingly concerned about the limited use of nuclear weapons by adversaries itself raises apprehensions. US allies wonder what impact such US concerns would have on its extended nuclear deterrence. Particularly worrisome is the idea that Russians are stepping up nuclear intimidation assuming that the level of US resolve to contemplate the use of nuclear weapons is low—or at least lower than that of Russia. This needs to be addressed by NATO and East Asian allies.³¹

Conclusion

While geographically distant, NATO’s European allies and Japan and South Korea are increasingly facing a similar set of challenges, including the issue of extended nuclear deterrence.The United States maintains a number of allies and partners across the globe, but only selected allies enjoy an explicit nuclear commitment—a privileged status, something an Australian expert calls “premium content” of extended deterrence.³² This suggests that in thinking about managing the extended nuclear deterrence relationship with the United States, NATO and East Asian allies need mainly to look at each other. That is exactly why it is imperative to move beyond the dichotomy between the NATO and East Asian models and seek a synergy.