Implications of the 2022–2023 Situation in Ukraine for Possible Nuclear Weapons Use in Northeast Asia

ABSTRACT

The Russian invasion of Ukraine in February of 2022, and the ongoing (as of this writing) conflict that has followed, has prompted many of the actors responsible for determining military and nuclear weapons strategy and policy to rethink their approaches. In Northeast Asia the combinations of the issue of nuclear weapons on the Korean Peninsula, tensions over Taiwan, and other regional disputes with the lessons of the Ukraine conflict have caused the nations of the region that have nuclear weapons, and those that do not but are covered under the US “nuclear umbrella”, to at least consider changes in how nuclear weapons might be deployed and, as a final resort, used. These actors include the United States, China, Russia, the Democratic People’s Republic of Korea (DPRK), the Republic of Korea (ROK) and Japan. This article compiles and summarizes the opinions of experts from or on each of these nations as to how the Ukraine conflict may influence perception of the utility and possible uses of nuclear weapons in Northeast Asia. The paper evaluates common changes in perception caused by the Ukraine conflict across the nations of the region, as well as differences, and notes the possible ways in which national changes in perception due to the Ukraine conflict may combine to make the danger of nuclear weapons use in the region even more serious than it has recently been. This article is based on work in the Project on Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA).

KEYWORDS:

• Nuclear weapons use
• Ukraine conflict
• nuclear proliferation
• nuclear sharing
• nuclear deterrence

Introduction

The Russian invasion of Ukraine in February of 2022 has, in the year (as of this writing) since it began, evolved into a conflict on the scale that Europe has not seen since World War II. Western powers in Europe and beyond, most notably the United States, have lined up in support of Ukraine, providing armaments and other aid, although not placing soldiers on the ground. Western nations have leveled economic sanctions on Russia and on some of Russia’s political and business leaders, hoping to make it more difficult and painful for Russia to prosecute its invasion, and ultimately to induce Russia to negotiate a peace settlement. Ukraine’s army have utilized Western support, plus their own considerable resolve and resourcefulness, in the defense of their country, and have thus far achieved a level of success in the conflict that has been unexpected to many. The combination of this success, and the Western support that enables it, appears to have surprised Russia’s leadership, who may have expected an easy victory and de-facto annexation of some or all of Ukraine back into the Russian sphere of influence.

Ukraine held thousands of warheads that were part of the Soviet Union’s (USSR’s) stockpile of nuclear weapons when the USSR dissolved in 1991, but agreed to give them up in 1994 in exchange for what it thought were security guarantees, in the form of the Budapest Memorandum signed by Russia, the United States, and the United Kingdom (for example, see Kelly and Lonsdorf 2022). The vast remaining nuclear arsenals of both Russia and the nations of the North Atlantic Treaty Organization (NATO), the defender of Europe, however, have meant that as the conflict in Ukraine has unfolded, the potential for nuclear weapons use has inevitably emerged as a further worry to policymakers, military strategists, and the public. These worries have been strengthened by statements by Russian President Vladimir Putin that have mentioned or included implied references to nuclear weapons. Whether or not President Putin has meant his statements to threaten adversaries with the use of nuclear weapons – different observers hold different positions on whether the statements were meant as actual nuclear threats – his statements have nonetheless been interpreted as threats of possible nuclear use by many (for example, see Negin 2023).

Although located at the other end of a very large continent from Ukraine, the Ukraine conflict and the changes in international relations that have come about as results of the conflict have nonetheless affected how the actors who determine security in Northeast Asia think about nuclear weapons deployment and strategy. These actors include those with territory in the region – China, Russia, Japan, the Republic of Korea (ROK), and the Democratic People’s Republic of Korea (DPRK)—and the United States, as the principal guarantor of security through nuclear deterrence and other means to the ROK and Japan, as well as (unofficially) to Taiwan. Of these, China, Russia, the United States, and the DPRK hold nuclear weapons, while the ROK or Japan are the beneficiaries of the US “nuclear umbrella”. Groups in both the ROK and Japan have at times pushed for more direct nuclear weapons capabilities. Changes in nuclear security thinking by these actors individually, in most cases, have arguably made nuclear weapons use more likely, or at least expanded the universe of circumstances in which nuclear weapons use might be plausible. When considering nuclear security in the region, however, the whole is greater than the sum of the parts, as the changes in nuclear security thinking and, potentially, in nuclear posture by each actor in response to the lessons of the Ukraine conflict from their own perspectives have the potential to exacerbate – whether through misinterpretation or otherwise – the potential for other actors to consider use of nuclear weapons.

In the Project on “Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA)”, the project participants – The Research Center for Nuclear Weapons Abolition, Nagasaki University (RECNA), The Nautilus Institute for Security and Sustainability, and The Asia-Pacific Leadership Network for Nuclear Non-Proliferation and Disarmament (APLN), have focused on the development and evaluation of plausible “use cases” for nuclear weapons in Northeast Asia, and on the development of policies to reduce the risk of nuclear weapons use in the region (RECNA-Nagasaki University, Asia Pacific undefined). “use cases” can be thought of as events and decisions leading to the use of nuclear weapons by one or more actors. As such, an understanding of how the Ukraine conflict may affect the potential for nuclear weapons use is a key to development and evaluation of a suitably inclusive and up-to-date range of plausible use cases.

To assess the potential impacts of the Ukraine conflict on nuclear security postures and potential nuclear weapons use in Northeast Asia, we asked experts from (or in the case of the DPRK, on) each of the Northeast Asian nuclear actors and the United States to address questions on the topics listed below. In each case, questions were targeted to nation-specific issues.

• How has or will perceptions of the war in Ukraine and the West’s response with sanctions and military aid affect attitudes about military build-up, nuclear deployment, and/or alert status in Northeast Asia?

• How might perceptions of the war in Ukraine and the West’s response affect consideration of nuclear weapons use in a conflict in Northeast Asia, whether accidental, due to misperception of the actions or intents of others, or intentional?

• Have assumptions about how much international support a potential adversary in the region might receive in the event of a military action changed thinking existing conflict hot spots?

• Do you see any of the potential nuclear weapons use cases presented in the NU-NEA Project’s Year 1 Report, Possible Nuclear Use Cases in Northeast Asia: Implications for Reducing Nuclear Risk, as being particularly affected (becoming more or less relevant, for example) by perceptions of the war in Ukraine and the West’s response, and if so, please describe briefly how those cases might be affected, or what additional potential cases might have become more important?

Some of the experts who agreed to provide input to this paper on the topics above were willing and able to publish their findings as short papers, while some preferred to provide input anonymously. The perspectives that we received from five experts have been published on the websites of the project participants as:

• “Implications of Russia’s Nuclear Signaling During the Ukraine War for China’s Nuclear Policy”, by Tong Zhao (Zhao 2022)

• “Potential Implications of the Situation in Ukraine for Russia’s Nuclear Deployment in Northeast Asia”, by Anastasia Barannikova (Barannikova 2022)

• “Birds of a Feather: Thoughts on Pyongyang’s Lessons from the War in Ukraine”, Alexandre Y. Mansourov (Mansourov 2022)

• “Implications of the Ukraine War for ROK Security”, by Cheon Myeongguk (Myeongguk 2022)

• Potential Implications of the War in Ukraine For Northeast Asia”, by Paul K. Davis (Davis 2022)

The remaining sections of this paper summarize the key lessons learned from the Ukraine conflict, and resulting changes in thinking about and approach to nuclear weapons doctrine and security more generally, from the perspectives of each of China, Russia, the DPRK, the ROK, Japan, and the United States. These findings are gleaned from the contributions listed above and other communications with colleagues in the region. The final two sections of the paper, respectively, suggest how the interactions of lessons learned in each country might increase the risk that nuclear and/or non-nuclear conflict might occur in Northeast Asia, and what national and international policies might be implemented to help ensure that the risks of nuclear conflict affected by those lessons are reduced.

Lessons Learned by China from Observing the Ukraine Conflict

Analysis suggests that China’s leadership fundamentally sees the Ukraine conflict as being caused by hegemonic behavior by the US-led West forcing Russia’s hand. China has been watching and learning from Russia’s implicit use of nuclear threat, and the lessons learned may add further ambiguity and uncertainty to the interpretation and application of China’s No First Nuclear Use policy in potential conflict situations, including those involving Taiwan.

In the face of Western sanctions on Russia and Western military aid to Ukraine, China has seen Russia’s nuclear “sabre-rattling” (implicit nuclear threats and “nuclear signaling”¹) as both justified and effective in making Western nations more cautious about providing miliary aid to Ukraine. Although China does not think that the perceived nuclear threats have made Russia more likely to actually use nuclear weapons, it has taken the lesson that the use of nuclear signaling is an important and effective approach to maintaining security and providing coercive leverage in times of tension or conflict. To the extent that China begins to use more nuclear signaling in its public rhetoric, its own No First Use (NFU) policy for nuclear weapons becomes more ambiguous. China’s No First Use policy “prohibits the first use of nuclear weapons by China but not the threat of first use of nuclear weapons in a conventional war”, thus adapting Russian nuclear signaling approaches can leave “‘wiggle room’ for China to maximize the coercive leverage of nuclear weapons without violating the letter of its NFU pledge” (Zhao 2022).

In addition, China has likely taken the lesson that Russia’s nuclear signaling during the Ukraine conflict has been effective in large part because of Russia’s vast nuclear arsenal. This lesson reinforces China’s resolve to continue to build and modernize its own nuclear arsenal.

Russia’s apparent revision of its own first nuclear weapons use policy to include, for example, perceived existential threats to the Russian state, has also likely been a lesson for China. That is, China may have taken Russia’s revision of its nuclear policies in times of conflict to imply that China could do so as well in times of crisis, “lowering the nuclear coercion threshold” and thereby expanding the potential circumstances under which nuclear weapons could be used. This potential to modify nuclear weapons use policies in time of crisis may serve to undermine the degree to which potential rivals have in peacetime NFU policies, and thus make building stable nuclear relations between rivals more difficult.

China will watch the success or failure of Russia’s attempt to use nuclear threat/nuclear signaling as a means to secure victory in Ukraine and take lessons from that outcome for its own policies about the role of nuclear weapons in helping achieve unification with Taiwan.

Implications of Lessons from the Ukraine Conflict for Russia’s Nuclear Posture in Northeast Asia

As a direct participant in the Ukraine conflict, the target of sanctions for its invasion of Ukraine, and the foe affected by the military assistance and other aid provided by the West to Ukraine, Russia can be expected to have learned a number of policy lessons from the conflict. Although the situation in Ukraine arguably does not directly affect Russia’s nuclear posture/strategy in Northeast Asia, indirect impacts of the situation in Ukraine on Russia’s nuclear policies in this region cannot be ruled out. Examples of potential indirect drivers of Russia’s policies include changes in nuclear weapons planning and deployment by the United States and China under the pretext or because of the Ukraine situation, changes in the nuclear weapons status of one or more of the non-nuclear states in the region, or the initiation of a military conflict over Taiwan or on the Korean peninsula.

Russia’s overarching nuclear doctrine has not changed in recent years. Barannikova (2022) notes that despite the ways in which some non-Russian officials and media have portrayed recent statements by Russian leadership, Russia’s nuclear doctrine remains guided by:

“ … The Basic Principles of the State Policy of the Russian Federation on Nuclear Deterrence of June 2020 – a document reflecting the most up to date nuclear doctrine of the Russian Federation – [which] lists the following factors that may affect Russian policy in the field of nuclear deterrence (and deployment):

“Build-ups of forces by potential adversaries, including nuclear weapons delivery systems, in territories adjacent to Russia;

“Deployment in NEA of anti-missile defense systems, cruise and ballistic missiles of medium and shorter range, or high-precision non-nuclear and hypersonic weapons; uncontrolled proliferation of nuclear weapons; and

“Deployment of nuclear weapons and their means of delivery on the territories of non-nuclear states.”

The European theater is generally considerably much more important to Russia in terms of its nuclear weapons policies and deployment than the distant Russian Far East. Nonetheless, Russia has important bases for nuclear-capable and nuclear-armed military infrastructure such as submarines in the region, and closely monitors the nuclear weapons status of the countries of the region and other regional actors, most notably the United States. Changes in how others deploy nuclear weapons in the region – with the exception of the ongoing Chinese nuclear build-up, which Russia does not see as a threat – would likely cause Russia to make changes in its own nuclear readiness. Such changes would include an enhancement or a withdrawal of US forces from the region, either of which Russia would see as upsetting the existing security balance. A specific example of a change in status that would concern Russia would be re-deployment of nuclear weapons on the Korean peninsula, either by the United States in coordination with the ROK or by the ROK itself, following breakout. Even ROK deployment of domestic nuclear-capable conventional weapons might cause Russia to reassess its own nuclear weapons deployment. Similarly, as the elements of the Australia/United Kingdom/United States agreement of 2021 are put into place (United States White House 2021; Goldstein 2021), Russia can be expected to reassess its own deployment of military assets in the Asia-Pacific Region. AUKUS was set in motion prior to the start of the Ukraine conflict, but Russia’s experience in Ukraine has likely made it even more sensitive to the military build-up and cooperation that AUKUS implies.

One key impact of the Ukraine conflict on both Russia and its rivals in the region has been the reduction in communications, including both leader-to-leader and military-to-military communications and communications arrangements, between Russa and the United States, Russia and Japan, and others. These reductions in communication may increase the potential for misunderstandings if a crisis occurs, including misunderstanding leading to higher risk of nuclear weapons use.

An outbreak of hostilities on the Korean Peninsula, or in or around Taiwan, particularly if joined by the United States, could cause Russia to change its nuclear weapons strategies, particularly if, for example, intercontinental ballistic missiles (nuclear-armed or not) or other armaments overfly Russian territory. Escalating military conflicts related to ongoing territorial disputes between the nations of the region could be another reason for Russia to consider using nuclear weapons. In each of these cases, Russia would be reacting to changes in weapons deployment and use by other actors, rather than leading in changing the status of nuclear weapons deployment.

Lessons Learned by the DPRK from Observing the Ukraine Conflict

Although it is certain that the DPRK’s leadership has watched the Ukraine conflict unfold with considerable interest, the lessons that the DPRK has learned from watching that conflict to date are probably not those that many Western observers posit. The Ukraine conflict has not affected how the DPRK thinks, positively or negatively, about the value of having its own nuclear arsenal, because, as Mansourov writes, the “North Korean leadership made up its mind on the strategic, military, political, and diplomatic value of the nuclear deterrent a long time ago, has no intention to give up its nuclear weapons, and needs no additional rationale to continue to strengthen its nuclear arsenal” (Mansourov 2022) The DPRK – in this case meaning DPRK Chairman Kim Jong Un, his national security advisors, diplomats, and DPRK armed forces planners – is unlikely to conclude from the Ukraine conflict that Russia and China are less trustworthy as strategic partners, but is deriving its lessons from what it sees happening in Ukraine.

Rather, the lessons that the DPRK learned from watching the Ukraine conflict are likely to be as follows:

• Even a weaker nation armed only with conventional weapons can resist a stronger nation armed with nuclear weapons if the former (such as Ukraine) has support from powerful allies (such as Western nations). What that might mean for the DPRK is that its strategic nuclear advantage over the ROK won’t make it more likely to prevail in a war with the ROK if the United States provides significant aid to the ROK.

• The DPRK will have observed the statements made by Russian leadership during the Ukraine conflict regarding the conditions under which Russia would use nuclear weapons. These statements might have induced the DPRK to have included similar concepts into its own nuclear use doctrine, namely, that the DPRK would use nuclear weapons only if the ROK and United States threaten regime change by targeting DPRK leadership, if the DPRK’s nuclear weapons, nuclear facilities, and/or military command and control infrastructure are threatened, or if the United States launched a pre-emptive nuclear strike on the DPRK. That is, absent these threats from the ROK and United States, the DPRK is unlikely to escalate from the use of conventional weapons to nuclear weapons in a Korean Peninsula conflict.

• The military support provided to Belarus by Russia, in part to counter what Russia sees as growing NATO support for nations on or near its border, may cause the DPRK to reconsider the benefits of “nuclear sharing”. Although previously unthinkable, the combination of the Ukraine conflict and increased US-China tensions may cause the DPRK to consider arrangements with China and/or Russia to share their nuclear weapons or nuclear-capable military technologies with the DPRK. Such nuclear sharing by the DPRK would be considered even more seriously if the DPRK perceived that the United States was considering forms of nuclear sharing beyond the status quo with its allies in the region, particularly the ROK but also Japan and possibly others.

• The exclusion of tactical nuclear weapons from US-Russia arms control agreements, and the reported movement of tactical nuclear weapons from central storage in Russia, may have reinforced for the DPRK that it should exclude tactical nuclear weapons from any agreement it might strike on its own nuclear weapons program, meaning that it could maintain tactical nuclear weapons anywhere on its own territory (for example, see Sanger and Broad 2022; Newsmax 2022).

• Attacks on the infrastructure at the Zaporozhiye Nuclear Power Plant (ZNPP), which each side in the Ukraine conflict claim have been launched by the other side, may have reinforced for the DPRK the utility of the vulnerability of nuclear reactor targets. Possible manifestations of this realization include the possibility that the DPRK could launch attacks on its own reactor at Yongbyon, if the Yongbyon site was controlled in a conflict by US/ROK forces, and that the DPRK could launch or threaten attacks on ROK nuclear reactors if a military conflict with the ROK broke out.

In combination, these lessons likely make the DPRK certainly no more likely to yield its nuclear weapons in response to either international pressure or as part of a negotiated settlement, and probably less likely, and also open up new avenues that could increase the risk of nuclear weapons use in the Northeast Asia region.

Lessons Learned by the ROK from the Ukraine Conflict

There are parallels between the geopolitical situations of Ukraine and the ROK in that both share a border with a nuclear-armed adversary, and both are supported militarily by Western allies, most notably the United States. The observation of how the Ukraine conflict is playing out has underscored for ROK political leaders and military planners the need for the ROK to maintain strong military alliances and to further develop its own conventional weapons capabilities. ROK analysts’ expectations as to the lessons that the DPRK has learned from the Ukraine conflict also play roles here, as the ROK expects that DPRK observations of the Ukraine conflict will further reduce the prospects for meaningful progress in talks on DPRK denuclearization. As a result, establishment of a nuclear arms control regime on the Korean peninsula is becoming, from the ROK perspective, one of the few remaining options for reducing the DPRK nuclear threat.

There has been no change as a result of the Ukraine conflict in the attitudes of the ROK public, or the position of the ROK’s executive branch of government, on the topics of either re-deployment of US tactical nuclear weapons in the ROK or the ROK’s own acquisition of nuclear weapons. The lessons of the Ukraine conflict have, however, made it more possible that future events, including a 7th nuclear weapons test by the DPRK or a withdrawal of the US nuclear umbrella from the ROK, could cause marked shifts in ROK positions.²

A key lesson absorbed by South Koreans from the Ukraine conflict has been the importance of having and maintaining powerful allies, and of having credible deterrents against aggression from powerful neighbors. The “ … Russian invasion of Ukraine has shown the [ROK] what could happen to a weaker country when it fails to maintain friendly relations with a stronger neighbor” (Myeongguk 2022). For ROK leadership, this lesson has reinforced the importance of maintaining the US military support, including the US “nuclear umbrella”, and also the importance of continuing to build up the ROK’s own conventional-weapon defensive capabilities. These particular lessons from the Ukraine conflict are not new, but have merely fortified lessons absorbed by Koreans from the many times in Korean history that the Korean peninsula has been invaded and, sometimes, dominated for years – the Japanese occupation of Korea from 1910 to 1945 being just one recent notable example (for example, see Cumings 2021). Specifically, what happened to Ukraine provides the ROK with an even stronger rationale for “maintaining its strong alliance with the United States and other partners, and in constructing an effective conventional military defense capability” (Myeongguk 2022).

Analysts and leaders in the ROK, as has often been the case in the period since the Korean War, have been obliged not only to think about how the lessons of Ukraine conflict might affect their own nation, but also about the lessons that their adversary across the demilitarized zone will be learning from ongoing events. Observers of the DPRK in the ROK – as have other observers of the DPRK (see above), posit that the DPRK has taken the lesson from Russia that nuclear threat, whether implicit or explicit, has significant value in deterring powerful potential adversaries. In addition, the ROK expects that the DPRK’s unwillingness to make any deal to give up or restrict its nuclear weapons capabilities will have, if anything, hardened as result of seeing what the Ukraine has gone through. As such, some ROK leaders may be more inclined to pursue a deal to establish a nuclear arms control regime on the Peninsula, rather than insisting on full denuclearization.

Public opinion polls in the ROK have shown a shift in recent years in favor of reintroducing US tactical nuclear weapons to ROK territory, and in favor of indigenous development of nuclear weapons, although the Ukraine conflict itself does not seem to have markedly affected public opinion on these questions as of yet. ROK leaders have not changed their policies on either of these shifts – and are against both redeployment of US weapons to the ROK and domestic production of nuclear weapons, but these positions could change in the future. A qualitative increase in DPRK provocations, such another nuclear weapons test, or a significant change in US support for the ROK, such as the removal of US troops from the ROK as proposed by then-President Donald Trump (for example, see Choi 2022), could cause ROK leadership to reconsider its stances on nuclear weapons sharing or development. If such events happen, it is likely that the lessons of the Ukraine conflict will be resonant for ROK policymakers, perhaps causing a swifter or stronger reaction toward nuclear weapons deployment than would otherwise have been the case.

Lessons Learned by the Japan from the Ukraine Conflict

The war in Ukraine has been followed with great interest by the public in Japan, as well as by policymakers. Both groups are keenly aware of the threats in the region posed by a China that is increasingly militarily assertive, by a nuclear-armed and authoritarian Russia, with which Japan has a long-running territorial dispute in the Kuril Islands (for example, see Barrash 2022), and by a nuclear-armed DPRK. The Ukraine conflict has made Japanese policymakers more interested exploring in how Japan can strengthen the credibility of its deterrence against possible adversaries, principally in relation to building or modifying its existing military cooperation with the United States. That is, with the Ukraine conflict in mind more people in Japan are in favor of talking about nuclear sharing – sharing the benefits, risks, and responsibilities associated with nuclear deterrence provided through deployment of nuclear weapons (North Atlantic Treaty Organization 2022)—but that does mean that those in Japan thinking about nuclear deterrence are more in favor of nuclear sharing, rather that they are feeling that it needs to be talked about.

Japan’s post-World-War II nuclear doctrine has been guided by the “three Japanese non-nuclear principles”, namely “not possessing, not producing and not permitting the introduction of nuclear weapons” (Ministry of Foreign Affairs, Japan. n.d..– the document is undated, but referencing a quote from Prime Minister Eisaku Sato from 1967). When considering whether to modify these three longstanding principles, Japan’s development or ownership of nuclear weapons is not popular, and NATO-type sharing of nuclear weapons is considered not possible, but there has been some consideration of lifting some restrictions allowing the United States to more flexibly deploy nuclear weapons in the area. Many others in Japan’s military and policy communities feel that it doesn’t make sense to make compromises on or change the nuclear principles now, as it is currently not the time to do so, but the consensus view is that there is a need to make deterrence more credible, more about conventional weapons, and to explore new domains of aspects of deterrence from Japan’s perspective. For example, there is talk among Japanese leadership, including within Japan’s most recent National Security Strategy (see Johnson and Dominguez 2022) of adding long-range strike capabilities, described as counter-strike capabilities (see, for example Nakamura and Okoshi 2023; Bennett 2022), in order to strengthen deterrence – the conflict in Ukraine seems to have added urgency to this discussion.

As with the ROK, some of the consideration of the lessons of the Ukraine conflict in Japan is focused on the lessons that other nations are learning. For example, some in Japan think that the Ukraine conflict might increase the possibility that Russia, as an authoritarian regime, might use nuclear weapons. Similarly, China and the DPRK are viewed as unpredictable, and if either of them starts a conflict in Northeast Asia, many Japanese see it as inevitable that the United States will join the conflict in some form, and Japan, given its hosting of US military bases in the region, would inevitably be drawn into such a conflict. If Taiwan is the next Ukraine, for example, Japan will not be able to keep that conflict at arm’s length, will have to defend Japanese territory, and will have to think about wartime resupply of munitions and other goods to itself and its allies, an issue underscored by what Japan and the rest of the world has been watching happen in Ukraine.³

Lessons Learned by the United States from the Ukraine Conflict

For the United States, as well as for other observers of the Ukraine conflict around the world, Ukraine’s defense of its territory has dramatized the importance of the actions of a state in its own self-defense, particularly if supported by strong allies. Observers have been generally surprised at how successful Ukraine has been at holding off much larger and better-equipped Russian forces, and even, in recent months, in reclaiming territory that Russia had captured. This success has certainly been aided and enabled by military assistance from the West, but has its roots in both Ukrainian determination to defend its territory and in Ukraine’s own preparations for a Russian invasion.

Having witnessed Ukraine’s defense of its nation, United States leaders are likely to be thinking about how the lessons of Ukraine will apply for the nations of Northeast Asia for whom the United States is a key guarantor of security, either officially or unofficially. Specifically, for the ROK, Japan, and Taiwan, the United States may, with the lessons of Ukraine in mind, be looking to each state to provide more toward its own defense in the future. That is, “[t]he notion of the United States protecting such states is perhaps giving way to a belief that it is plausible and appropriate for such states to largely defend themselves” (Davis 2022). This evolving belief may, in the future, result in more or less pressure for the United States’ Northeast Asia allies to arm themselves depending on who the US president is as of 2025.

Although the United States and other Western nations have provided considerable military assistance to Ukraine, that assistance has stopped short of involving US and NATO troops directly in the conflict. This reluctance to send troops into battle in Ukraine has in part been because Ukraine is not a member of NATO, but also in large part because the United States and its Western allies fear escalation to a nuclear conflict. This fear of escalation may, in a future conflict in Northeast Asia, serve to limit US involvement, for example, to high seas or air space support of Taiwan, were it to become involved in a military conflict with China.

Although it is not yet evident that the conflict in Ukraine is changing how US policymakers and military planners think about deploying nuclear weapons in or how to respond to conflicts in Northeast Asia, the conflict in Ukraine might change how the United States thinks about its Northeast Asian allies having independent nuclear capabilities, A guiding objective of US policy in the region to date has been nonproliferation of nuclear weapons, but the Ukraine conflict may make some groups of US policymakers wonder whether it might in fact be prudent for some allies to have their own nuclear deterrent. The possible “tolerance” of an independent nuclear deterrence capability on the part of US allies may be particularly likely if it proves politically or socially difficult or unaffordable for those allies to develop a sufficient conventional capability to deter a nuclear-armed adversary from attacking.

Paul Davis concludes his essay on the impacts of the Ukraine conflict on nuclear posture and nuclear diplomacy in Northeast Asia with the following suggestions for “statesmen and scholars” in the United States and beyond:

• “Acknowledge the plausibility of war, the importance of nuclear weapons, and the potential usability of nuclear weapons for some purposes in war.

• “Acknowledge the very questionable credibility of extended nuclear deterrence when the potential aggressor has nuclear weapons that can strike the United States.

• “Embrace the opportunities for advanced allies to achieve conventional deterrence by denial with precision weapons and intelligence.

• “Urge allied investments in effective self-defense that exploits this modern technology. Reallocate investments accordingly, shifting to investments with the most defensive leverage.

• “Urge that such investments be as manifestly defensive as possible, so that it is difficult for China to see them as a security threat. Publicize, exercise, and discuss the defensive nature of preparations at every opportunity”.

• “Simultaneously, negotiate to establish rules of the road and better mutual understanding of realities, actions, and signals. Indeed, if the vulnerable states more actively prepare for stalwart self-defense, and perhaps for independent nuclear deterrents, prospects for regional arms control might improve”.

Interactions in Changes in Nuclear Posture Among Countries

To this point in this paper the lessons learned from the conflict in Ukraine by the Northeast Asia nuclear actors and their allies have been considered largely independently. These lessons, however, are neither learned nor acted on in a vacuum. Each change that each state makes or even contemplates in response to the lessons of the Ukraine conflict has the potential to bring a response from its adversaries and, in some cases, allies. In some cases, these responses will arguably increase the risk of nuclear weapons use in the region.

Specific examples of such interactions could include:

• As states such as the ROK and Japan build their defensive capabilities and/or manifest closer military ties and coordination with the United States, and Taiwan does the same, China, Russia, and/or the DPRK may conclude that their strategic advantage as nuclear weapon-equipped states may be eroded. This may make those states more likely to mis-identify actions such as space launches, missile tests, or joint military exercises as impending existential threats, and increase the possibility of nuclear first use.

• Relatedly, if the ROK, Japan, and/or Taiwan shift or appear to be ready to shift their non-nuclear postures, China, Russia, and/or the DPRK may consider using nuclear weapons before their nuclear advantage is eroded.

• The lessons of the importance of strong allies learned from the Ukraine conflict may make the potential withdrawal of US support, if there is a political shift in the United States, a greater concern for US allies in the region. Those allies may therefore adopt contingencies in case US support is withdrawn that will be watched and reacted to by their adversaries.

• As the United States urges and supports its allies in the region to develop their militaries and defensive armaments, and particularly to the extent that those allies do so, their adversaries in the region will likely feel obliged to build their own capabilities. If China, Russia, or the DPRK reaches the point where they feel that their nuclear advantage will soon disappear, and particularly if they feel under threat, its use of nuclear weapons may become more likely.

Conclusions

The lessons of the Ukraine conflict for the nations of Northeast Asia, as well as for the United States as a key guarantor of security in the region, vary by country and area, but have likely included:

• A smaller, nominally weaker state without nuclear weapons can mount a successful defense against a larger, nuclear-armed state if it has a combination of sufficient will and planning for its own defense coupled with support from and good relations and close coordination with powerful allies.

• That said, the possession of nuclear weapons serves as a powerful deterrent to attack or counter-attack by adversaries, either for a larger aggressor nation or for a smaller nation defending its territory. If the deterrent effect of the US nuclear umbrella, or the commitment of the United States to providing a nuclear umbrella in the region, is somehow called into question, this can be a lesson that may cause the ROK, Japan, and/or Taiwan to re-think their non-nuclear status in different ways.

• More extensive development of conventional weapons capabilities is desirable, both on the part of individual nations and, from the perspective of the United States, for its allies in Northeast Asia.

• Modification or perceived modification of nuclear No First Use policies on the part of some actors in Northeast Asia, including in response to conventional arms build-ups by other actors, would likely further destabilize the nuclear security regime in the region and globally.

Changes in the deployment of both conventional and nuclear weapons by one or more actors in Northeast Asia are likely to have knock-on effects related to the deployment and alert status of nuclear forces by other nuclear actors in the region, arguably increasing the potential for nuclear weapons use as a result of, for example, misunderstanding of others’ military intentions.

Apart from international diplomacy to address the underlying issues driving conflicts between the nations of Northeast Asia – a topic that is well beyond the scope of this paper⁴—potential policies to manage increased nuclear risk arising from the lessons nations are learning from the Ukraine conflict include:

• Improving leadership-to-leadership and military-to-military communications between adversaries and allies alike, including during periods of heightened tension between nations, to reduce the potential of misapprehension of military threats that might lead to nuclear use.

• Emphasizing the defensive nature of any military upgrades.

• Continue to press for nuclear weapons control agreements, including with the DPRK.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the Nagasaki University Asia-Pacific Leadership Network .

Notes

¹ “[S]ignaling by rhetoric and/or actions involving some aspect of nuclear operations that nuclear weapons might be used against adversaries” (Zhao 2022).

² Such a possibility was indicated, although later recanted, early in 2023 in a speech by ROK President Yoon Suk-yeol (Mohan 2023). Mohan notes “To be clear, South Korea is not actively pursuing homegrown nuclear weapons. However, the incident demonstrated an increased tolerance for casually suggesting nuclear proliferation”..

³ Japan has, for example, limited domestic supplies and production of munitions, so security people in Japan will need to think through how Japan would be resupplied in the event of a conflict in Northeast Asia.

⁴ Examples of such underlying issues include, but are by no means limited to, great power economic conflict, clashes related to differences in political systems, the impact of internal politics and social movements on external relations between states, regional territorial disputes, nuclear and conventional weapons arms races and disarmament agreements, and conflicts related to the international aspirations of national leaders.