Overview

Introduction

Alarmed by the growing security challenges posed by North Korea and China, the United States, Japan, and South Korea have taken unprecedented steps over the past year to expand their trilateral cooperation.

At the Camp David summit in August 2023 with U.S. President Joe Biden, Japan’s Prime Minister Fumio Kishida, and South Korea’s President Yoon Suk-yeol, the three leaders agreed on a range of collective initiatives to boost their military coordination and combat readiness in regional contingencies.¹They issued a joint statement from Camp David expressing criticism of North Korean and Chinese aggression, indicating that confronting threats posed by North Korea and China would be a major — if not the main — strategic objective of the trilateral partnership. Some observers assessed the summit as laying the groundwork for a future trilateral military alliance against North Korea and China.²

The tightened Japan–U.S.–South Korea trilateral military alignment has accompanied assertive bilateral and individual security policies and postures to counter North Korean and Chinese threats. In implementing its “Pacific Deterrence Initiative” to counter China, Washington has sought to upgrade U.S. forward military presence and operational control in the Asia–Pacific through its regional alliance structure.³ Under the Yoon administration, Seoul has adopted an explicit preemptive strike posture against North Korea. Tokyo has revised its national security strategy to acquire offensive capabilities, increase its defense expenditures, and promote a more combat–ready defense posture in cooperation with the United States.⁴

Trilateral security cooperation can certainly contribute to deterring North Korea’s aggression and counterbalancing China’s regional military presence. However, a one–sided emphasis on military deterrence can be counterproductive by causing greater North Korean and Chinese military assertiveness. 

Conflict deterrence is essentially about shaping a potential aggressor’s cost–benefit calculus.⁵ Deterrence thus requires not only emphasizing the costs of aggression through sufficient military threats but also credibly reassuring the potential aggressor that the purpose of deterrence is not to undermine its vital interests. A holistic view of deterrence will create opportunities for mutual restraint and stabilization of confrontational dynamics. An effective strategy to deter North Korea or China would thus need to reduce rather than exacerbate their insecurities.

The dilemma Washington, Tokyo, and Seoul face is that specific policies or postures they have pursued or plan to pursue to improve security can trigger some of the deepest North Korean and Chinese insecurities — that is, the North Korean fear of regime change and the Chinese fear of losing Taiwan forever. A Japan–U.S.–South Korea trilateral security partnership that reinforces these North Korean and Chinese fears will feed into Pyongyang’s belief that there is no better alternative than continually expanding its nuclear arsenal and Beijing’s belief that U.S. efforts to bolster regional military alliances are driven by an ulterior motive to keep Taiwan permanently separated from China. As a result, North Korea and China could be compelled to opt for more confrontational policies instead of restraining their behavior.   

This policy brief examines how the Japan–U.S.–South Korea trilateral partnership could worsen the existing security dilemmas with North Korea and China and offers a roadmap for trilateral cooperation to mitigate these security dilemmas and stabilize the region.

Worsening regional security dilemmas

Risk of reinforcing North Korean fears of regime change

The deep–rooted North Korean fear of U.S.–instigated regime collapse, no matter how overblown it may be, has long contributed to Pyongyang’s belief that only nuclear weapons can guarantee its survival. Indeed, at least since the early 2000s, consecutive U.S. administrations have talked of regime change in North Korea as a desirable outcome.⁶Having witnessed repeated U.S. attempts to change regimes or assassinate leaders in perceived rogue states such as Libya, Iraq, Afghanistan, and Syria over the years, it would be unsurprising if Pyongyang were convinced of a U.S. motive to remove the North Korean regime. Indeed, Pyongyang once warned the United States,“This land is neither the Balkans nor Iraq and Libya.”⁷

North Korea’s military policies over the years make more sense when taking its fears of U.S–mobilized regime collapse into account. North Korea’s obsession with developing intercontinental ballistic missiles (ICBM) capable of targeting American territory can be understood as a pursuit of deterrence rather than a preparation for a suicidal attack on the United States. North Korea’s nuclear law revisions in 2022 — shifting from a no–first–use stance to “automatic and immediate” nuclear retaliation against any attempted attacks on the North Korean leadership — can also be understood along the same lines.⁸

Promoting regime change is not a formal policy of the United States, South Korea, or Japan. But whether North Korea believes this is a different matter. Since the theory that strident sanctions can elicit North Korea’s regime collapse was once widely endorsed by American, Japanese, and South Korean leaders, Pyongyang probably believes this is still the case.⁹

If enduring threat perceptions about regime survival play a decisive role in the North Korean cost–benefit calculus of pursuing nuclear weapons, deterring such outcomes depends in no small part on reducing North Korean anxiety about regime change.¹⁰However, by relying on offensive military strategies and doctrines to deter North Korea, which will further overshadow the defensive intentions of deterrence, the Japan–U.S.–South Korea trilateral partnership risks stiffening the North Korean resolve to keep building nuclear weapons.  

Under the Yoon administration, Seoul has adopted a crystal–clear preemptive strike posture, placing concepts of preemption and automatic retaliation at the forefront of its defense strategy.¹¹Seoul has focused much on enhancing capabilities to preempt North Korean missile launches and developing operational strategies to remove North Korea’s nuclear control command, namely the leader Kim Jong Un, in the event of war with precision missiles or special decapitation operation forces.¹²

While the Biden administration has avoided a preemptive posture toward North Korea, it has made a clear commitment to automatic regime–ending retaliation against North Korea if it used nuclear weapons.¹³ Washington has also reportedly resumed special operation drills with Seoul to simulate North Korean leadership decapitation that had been suspended for years.¹⁴

Japan revised its national security strategy in 2022, which mandates the acquisition of “counter–strike” missile capabilities and marks a departure from its traditional strictly defensive defense posture.¹⁵ As a result, Japan is purchasing U.S. precision–strike Tomahawk cruise missiles capable of targeting North Korean and Chinese territory and plans to develop its own long–range missiles. Although the Japanese rationale for these missiles is to deter attacks by having a retaliatory capability, these systems could allow Japan to move towards a preemptive posture in the future.¹⁶

Various initiatives launched at the Camp David summit serve to enhance trilateral capabilities and coordination to strike North Korea. For example, the trilateral real–time intelligence sharing system on North Korean missile activities has enabled more accurate tracking of the origins of North Korean missile launches, hence the possible targets of preemption and counterstrike. 

Based on indications so far, there appears to be potential for Washington, Tokyo, and Seoul to pursue an assertive trilateral posture against North Korea as they coordinate on strengthening deterrence, possibly even a preemptive posture.¹⁷ Such appeals will exist in light of Pyongyang’s continued progress in acquiring various types of tactical nuclear capabilities, which could substantially lower the North Korean threshold to use nuclear weapons.¹⁸

However, emphasizing preemption and counterstrike may prove counterproductive to deterrence. This policy might restrain Pyongyang’s coercive behavior to some degree and deter conflict in the short run, but it will also reinforce Pyongyang’s fatalism — i.e., that only by developing more powerful nuclear weapons and effective delivery systems, and showing ever–stronger resolve to use them, can they guarantee the regime’s protection and survival. In short, future military escalation and conflict will become more dangerous and destructive. The current Japan–U.S.–South Korea trilateral approach to North Korea neglects the importance of security assurances for effective deterrence. By failing to provide adequate assurances that would alleviate Pyongyang’s resolve to keep building nuclear weapons or employ nuclear weapons in a crisis, the current trilateral trajectory risks exacerbating the existing confrontation. 

Risk of reinforcing Chinese fears of Taiwan’s permanent separation

The Japan–U.S.–South Korea trilateral partnership also risks provoking greater Chinese military coercion by overlooking the importance of reassurance for deterrence on the Taiwan issue. 

Numerous studies of a hypothetical U.S.–China war over Taiwan has revealed that the cost for China of invading Taiwan is enormous, with a considerable risk of failure.¹⁹ At a minimum, such a war would wreck the Chinese economy and significantly damage China’s military capacity.²⁰ Despite the high cost of war, Beijing has a strong incentive to engage in severe confrontation and even use military force to prevent Taiwan’s independence (or permanent separation).²¹ Chinese leaders have long regarded unification with Taiwan as a vital interest linked to the Chinese Communist Party’s legitimacy and have expressed their resolve to use force if that vital interest were threatened — for example, by what it perceived as U.S. and/or Taiwanese attempts to permanently separate the island from mainland China.²²

For Beijing, the possibility of losing a war with Taiwan might be a less decisive factor when weighing the use of force, because backing down would be perceived as more costly. Even when China was substantially weaker than it is now and had no chance of winning a conflict against the United States, it did not hesitate to demonstrate its strong commitment to preventing Taiwan from moving toward independence, as in the 1995–96 Taiwan Strait Crisis.²³ Dissuading Beijing from using force against Taiwan requires not only military deterrence but also credible reassurance that the purpose of deterrence is not to promote Taiwan’s permanent separation. Failing to do the latter would increase the likelihood of China choosing to use force.

Because Washington, Tokyo, and Seoul have yet to develop a concrete trilateral approach to the Taiwan issue that combines deterrence with credible reassurance, Beijing might interpret their current security initiatives as part of a coordinated effort to keep Taiwan permanently separated from China.

For example, in recent years, there appears to have been backtracking from previous U.S., Japanese, and South Korean commitments to their respective One China policies. 

With the United States now focused on strategic competition with China, some in Washington view the Taiwan issue as a geostrategic problem and believe that keeping Taiwan separated from China at any cost is now essential for regional stability and the overall U.S. defense posture. This notion appears to have influenced the U.S. government, with a senior Biden administration defense official describing Taiwan as a vital strategic node in Asia — thus implying that it must be kept separate from China.²⁴

The apparent U.S. rhetorical emphasis on the geostrategic value of Taiwan, combined with President Biden’s repeated statements that U.S. forces would defend Taiwan if China were to attack Taiwan, have put into question the longstanding U.S. commitment to refrain from a military commitment to permanent Taiwan independence.²⁵While U.S. officials have continued to espouse fealty to the One China policy, such reassurances now ring hollow to Beijing in light of repeated rhetorical backtracking, U.S.–Taiwan political engagements that appear increasingly official, and ever–growing U.S. military support for Taiwan.²⁶

Japan’s statements on the Taiwan issue have also backtracked over the years. After Sino–Japanese normalization in 1972, Japan regularly reaffirmed the mutual understanding with China that constitutes its version of the One China policy — there is only one China²⁷; Japan respects the Chinese position that Taiwan is a part of China²⁸; Japan does not support Taiwan independence²⁹; and Japan will continue to maintain only unofficial exchanges with Taiwan.³⁰The Kishida government, however, is now reluctant to mention the notion of “One China” and  explicitly state non–support for Taiwan independence even though the Biden administration has routinely reaffirmed U.S. non–support for Taiwan’s independence.³¹ 

Meanwhile, Japan has expanded its political and military engagement with Taiwan. Japanese leaders are frequently visiting Taiwan and making forward–leaning statements about defending Taiwan. For example, in August 2023, during his visit to Taiwan, former Prime Minister Tarō Aso, who currently is the vice president of the ruling Liberal Democratic Party, stated that Japan must show its “determination to fight” to deter China from attacking Taiwan.³² Previously, a retired Japan Self–Defense Force officer has served as the de facto Japanese defense attaché in Taiwan. But now, a current Ministry of Defense official will reportedly serve in this role to interact with Taiwan’s military.³³

Likewise, South Korea has become more reluctant to reaffirm its bilateral understandings with China reached at the 1992 China-South Korea normalization, which constitutes its version of the One China policy.³⁴South Korea used to confirm its One China policy in authoritative documents and statements at the presidential level.³⁵But in recent years, starting with the previous Moon administration and continuing under the current Yoon administration, South Korea has tended to endorse its One China policy only at the ministerial level and in an increasingly less formal and less public manner.³⁶ For example, South Korean officials have espoused their fealty to the One China policy in bilateral exchanges with Chinese counterparts, but such reaffirmation has tended to be excluded from official readouts.³⁷ 

While South Korea has refrained from political and security engagement with Taiwan over the years, this norm may be shifting under the Yoon administration. The Yoon administration’s recent invitation of a Taiwanese official to deliver a video speech at the U.S.–led Summit for Democracy held in Seoul, where the official asserted Taiwan is not a mere democratic island, may have been a harbinger of more official–looking South Korea–Taiwan exchanges to come.³⁸

Washington, Tokyo, and Seoul’s rhetorical backtracking and de–emphasis on their One China policies could undermine deterrence. The three governments have now adopted a firm trilateral stance against Chinese attempts to achieve unification by force by stating their opposition to unilateral attempts to change the status quo.³⁹There is nothing inherently wrong with this clear trilateral opposition to unification by force. This message, however, when accompanied by a weakening of previous “One China” understandings, can signal to Beijing that such trilateral affirmations reflect part of a larger strategy intended to ensure Taiwan’s permanent separation from China. Convincing Beijing that this is not the case will not be easy, but it is necessary to preserve holistic deterrence through credible reassurance and motivate Chinese restraint with respect to Taiwan. 

Risk of precipitating a Russia–North Korea–China trilateral

As North Korea and China view the tightening Japan–U.S.–South Korea military partnership as posing greater challenges to their core interests (regime security and unification with Taiwan, respectively), North Korea and China could enhance their security ties and even pursue a trilateral strategic partnership with Russia. 

There is a historical precedent for the three countries working together: in the first decade of the Cold War, China, North Korea, and Russia were committed to cooperating against the West in the name of anti-–imperialism and collaborated in the Korean War. In recent years, the China–Russia and North Korea–Russia bilateral relationships have deepened as the U.S.–China rivalry and the Ukraine War increased their need for cooperation. 

A shared antagonism against the United States has driven China and Russia to bolster military cooperation such as intelligence sharing, joint weapons development, and more frequent and expansive joint military exercises in regional maritime and air spaces.⁴⁰Russia’s isolation from the West following its full–scale invasion of Ukraine in February 2022 provided an opportunity for North Korea to elevate cooperation with Russia. Leveraging Russian needs for munitions and political support for its war at the United Nations, Pyongyang has obtained greater Russian military technological assistance and economic support for circumventing sanctions.⁴¹

China has so far maintained a distance from the emerging North Korea–Russia partnership for a couple of possible reasons. First, the deep historical mistrust between Chinese and North Korean leaders has kept their relationship fragile.⁴²Another factor might be Beijing’s cost–benefit calculation that drawing closer to North Korea and Russia could severely damage its global reputation and provoke a deeper anti–China coalition among the United States, Japan, South Korea, and other regional actors.⁴³

Nonetheless, China’s stance on North Korea has become more tolerant in recent years. In the past, China had endorsed extensive U.N. sanctions against major North Korean provocations, such as intercontinental ballistic missile (ICBM) tests, most recently in 2017. But China has since become far less willing to support punitive measures against North Korea and reluctant to condemn North Korean provocations.⁴⁴

Beijing’s increased reluctance to pressure North Korea may go beyond the longstanding Chinese fear of a regime crisis in Pyongyang caused by external pressure. Increasingly alarmed about U.S. regional containment, Beijing may now be more willing to tolerate Pyongyang’s nuclear ambition and might even eventually partner with a nuclear North Korea in a confrontation against the United States and its regional allies.⁴⁵Such a major shift in China’s value perception of North Korea might become more likely in the context of growing Chinese suspicions that the emerging Japan–U.S.–South Korea trilateral military partnership is supporting a U.S. containment strategy to keep Taiwan permanently separated from China. 

The emergence of a Russia–North Korea–China trilateral alignment will no doubt further destabilize northeast Asia’s security environment and intensify regional tensions. For example, Russia, North Korea, and China may begin trilateral joint military training and exercises in order to counter Japan–U.S.–South Korea joint drills.⁴⁶Specifically, Beijing could become more inclined to undertake such actions if Japan–U.S.–South Korea naval and aerial drills — so far mostly taking place near South Korean territory — start appearing more directed at China by moving closer to the Taiwan Strait or other disputed maritime locations.⁴⁷ 

Additionally, North Korea might become more emboldened to engage in provocative nuclear weapons tests. Previously, China’s opposition to (and willingness to punish) North Korean nuclear tests had raised the cost of nuclear tests high enough to at least restrain Pyongyang from testing nuclear weapons more frequently.⁴⁸Without such pressure from China, Washington, Tokyo, and Seoul would face Pyongyang with a completely free hand to test new tactical nuclear weapons it develops.  

As depicted above, the likelihood of deeper regional friction and confrontation calls into question the wisdom of framing the regional order in Asia as a contest between democracy and autocracy or making “values–based diplomacy” the guiding principle of cooperation.⁴⁹This ideology–oriented framework will undercut Chinese incentives to pressure North Korea and provide a rationale for trilateral military cooperation between China, North Korea, and Russia.

The Japan–U.S.–South Korea trilateral’s transition into an overtly anti–authoritarian, anti–North Korea, and anti–China coalition could also backfire by creating echoes of the imperialist past, which could incite nationalist passions in both China and North Korea and exacerbate geopolitical polarization. Japan’s seizure of Taiwan after the first Sino–Japanese War of 1894–95 is indelibly etched in China’s collective memory. Therefore, the Chinese will be defiant against Japanese cooperation with the United States and South Korea to impede Taiwan’s eventual unification with China.⁵⁰North Korea could see the U.S.–Japan security partnership with South Korea as echoing the history of outside imperialists enlisting Korean collaborators, as in Japanese colonialism in the first half of the 20th century or the Cold War alliance between the United States and South Korean dictators.

Reorienting the trilateral to stabilize northeast Asia

Promote stability as the guiding principle in deterring North Korea

Having developed tactical nuclear weapons, which allow limited, low–yield nuclear strikes, Pyongyang may no longer regard using nuclear weapons solely as the last resort to deter war or counter an offensive regime change attempt but also as a means of strategic deterrent and “escalation control” in crises.⁵¹Such misguided North Korean confidence in controlling escalation raises the possibility of using nuclear weapons in a crisis.⁵²Because of North Korea’s increasing strategic flexibility in employing nuclear weapons, the so–called deterrence by punishment to compel North Korea by threatening preemption or automatic regime–ending retaliation bears an increasing risk of nuclear escalation and conflict.  

To underline a stronger resolve to counter North Korean attacks, some experts have raised the need for a U.S. declaration to preempt North Korean missile launches.⁵³Despite reflecting an understandable concern, the policy of preemption carries a significant risk and should not be considered. It can backfire by triggering Pyongyang to take a more aggressive first–use posture, pursue dangerous operational plans to employ nuclear weapons early in a crisis, and most obviously, keep expanding and diversifying its nuclear arsenal.⁵⁴And as North Korea becomes more belligerent, it can tempt Japan to move closer to a preemptive posture. Such a trend toward a Japan–U.S.–South Korea trilateral preemptive posture may prove to effectively threaten North Korea but only to stimulate its nuclear ambition.  

In deterring North Korea, Washington, Seoul, and Tokyo should remember that the key goal is defusing — not fueling — Pyongyang’s resolve to expand its missile capabilities, build more nuclear weapons, and use them. Therefore, the three countries should avoid moving toward a trilateral preemptive posture and roll back their respective offensive rhetoric and policy that might further provoke rather than deter North Korea. Seoul’s recent emphasis on preemption and counterstrike and Washington’s routine threats of regime-ending retaliation are examples of such counterproductive provocation.⁵⁵

In particular, Washington and Tokyo should encourage the Yoon administration to take a more restrained posture toward North Korea. In the event of a North Korean gray-zone provocation, South Korea’s prudent restraint will be necessary to prevent an inadvertent escalation with North Korea into an unwanted larger conflict that the United States and Japan could be dragged into.⁵⁶

Furthermore, Washington, Tokyo, and Seoul should moderate the scale and tempo of joint exercises. In policy debates on the implications of joint exercises for the deterrence of North Korea, the conventional wisdom has been that more frequent and larger exercises are better for deterrence.⁵⁷Many experts have thus tended to oppose reducing or postponing joint drills for the sake of accommodating North Korea, believing that it will weaken deterrence and invite aggression or decrease South Korean and Japanese confidence in the U.S. alliance commitment. 

However, research has found that a restrained approach to joint military exercises can benefit deterrence by stabilizing crisis dynamics on the Korean peninsula.⁵⁸Another recent study has shown that South Korea’s sense of confidence in the U.S. extended deterrence has not gone up over the past two years despite the augmented U.S. rhetorical commitment to automatic retaliation against North Korea and the increase in joint exercises.⁵⁹This raises doubts about the benefits of employing regime-threatening rhetoric or joint exercises as a means of ally reassurance at the cost of provoking North Korea and escalating tensions. 

These findings leave room for continued regular joint exercises but suggest that they should be moderated and designed not to undermine stability. The trilateral and bilateral military displays currently taking place on a regular basis involving U.S. nuclear assets, such as B–52 bomber overflights, could be downscaled since they can provoke North Korea without necessarily achieving either goal of signaling credible deterrent threats or reassuring allies.⁶⁰

Dealing with North Korea becomes easier when its behavior is more predictable, and this partly depends on the North Korean leadership’s sense of predictability about its security. If certain joint exercises hold the potential to augment Pyongyang’s irrational decision–making that can lead to dangerous miscalculations and overreactions, those may not be worth practicing at all.⁶¹

Credibly reassure China on the Taiwan issue

In order to promote stability in the Taiwan Strait, the United States, Japan, and South Korea should cooperate to credibly reassure China on the Taiwan issue. While the role of the United States as a primary actor in the problem will be particularly critical, Japan and South Korea’s role will also be important, given their increasing relevance to the strategic context of the U.S.–China rivalry as two key American military allies in northeast Asia. 

To this end, the three countries together should clearly and explicitly confirm in official statements their One China policies and declare that they oppose unilateral changes to the status quo by any side, do not support Taiwan independence, and will accept any resolution of the Taiwan issue (including unification) achieved by peaceful and non–coercive means.⁶²

Additionally, Washington, Tokyo, and Seoul should pursue cooperation and engagement with Taiwan on a strictly unofficial basis. Once Taiwan’s new president–elect, Lai Ching-te, a long-time ardent pro–independence advocate, enters office in May, he may very well be poised to elevate ties with the United States, Japan, and South Korea in a more official–looking manner and build overall greater regional support for Taiwan.⁶³ The danger here is that staunch trilateral support for Taiwan and antagonism toward China can feed Lai’s pro–independence instincts and drive a misjudgment that he is gaining unprecedented regional support to move toward independence. The possibility of such a scenario should give Washington, Tokyo, and Seoul incentive to keep their relationships with Taiwan strictly unofficial and be selective about the nature of cooperation with Taiwan.  

Adopt a defensive-denial approach to Taiwan contingency planning

A growing number of U.S. experts and strategists have argued that as the status quo in the Taiwan Strait becomes more strained, Taiwan contingency planning will be inevitable for Japan and South Korea, given their geographical locations, the large U.S. military presence on their territories, and the hefty cost a Taiwan conflict will impose on their security.⁶⁴Indeed, frank bilateral and trilateral discussions on a Taiwan contingency can help clarify each other’s positions and adjust expectations. Due to various factors, including the fear of entrapment and domestic resistance, Japan and South Korea face limitations in terms of how far they can be involved in a Taiwan contingency. 

Polls have suggested that the majority of Japanese and South Korean citizens believe their militaries should only provide rearguard support to the U.S. military in a Taiwan contingency.⁶⁵Overall, the Japanese and South Korean public does not support the direct involvement of their countries’ military in the defense of Taiwan.  

Moreover, greater Japanese and South Korean involvement in Taiwan contingency planning with the United States could signal to Beijing that Washington is abandoning its longstanding policy of strategic ambiguity and adopting a policy of strategic clarity regarding whether and how to respond to a Taiwan conflict. China might see such developments as major provocations and take a more offensive military posture against Taiwan, Japan, and South Korea, further ramping up its military muscle-flexing against Taiwan and gray-zone activities in Japanese and South Korean maritime and air spaces.⁶⁶

In sum, overt American efforts to involve Japan and South Korea in joint military planning and operations to directly defend Taiwan not only exceed the public consensus in Japan and South Korea but can also fuel antagonism between China and Taiwan, between China and Japan, and between China and South Korea. 

The more militarily and politically feasible approach to preparing for a Taiwan contingency may be a “defensive-denial” posture in which Japan and South Korea primarily focus on defending their territories and providing rearguard support to the United States.⁶⁷

To deter a Taiwan conflict, Japan should adhere to its strictly defensive doctrine and strengthen its defense capabilities and preparation so that its Self-Defense Forces, as well as U.S. military deployments in Japan, are more survivable, resilient, and mobile in the context of Chinese offensive military operations against Japan and Taiwan. Given the geographic proximity of Japan’s southwest island chain to Taiwan, a Japanese “defensive-denial” strategy would also complicate Chinese military plans to unify Taiwan with the mainland with force, thereby enhancing deterrence.⁶⁸Such a strategy to defend Japanese territory and only play a rearguard support role would be less provocative to China than direct and frontline Japanese involvement in Taiwan’s defense.

Because South Korea faces the risk of North Korea’s opportunistic aggression in the event of China’s invasion of Taiwan, it makes sense for South Korea to keep its defense posture and deterrence capabilities oriented around the Korean peninsula contingency.⁶⁹And given South Korea’s military concentration on land forces, its ability to partake in direct combat operations, which would necessitate sufficient naval and air capabilities, may be limited. These structural limits suggest that a “defensive–denial” strategy to focus on territorial defense and limited rear–area support for the United States may also be the most suitable role for Seoul in a Taiwan contingency. 

Seek inclusive economic and diplomatic engagement with China.

In the name of “de–risking,” the United States has made restricting the influx of advanced technological materials and investments into China a strategic priority, with a stated goal of limiting Chinese access to a selective number of advanced technologies with military implications that have “straightforward national security concerns”—described as “small yard, high fence” restrictions by the U.S. government.⁷⁰

To enhance the strategy’s impact, Washington has sought to make sure other countries join the effort. Japan and South Korea — U.S. allies and top players in the global semiconductor and advanced technological value chain — are no exceptions. Japan is already involved in the effort, and while South Korea has yet to join, the Camp David trilateral commitment to cooperating on advanced technology supply chain resilience hinted at the possibility of future trilateral cooperation in choking off Chinese access to advanced technology.⁷¹However, going in this direction of “trilateral de–risking” could substantially heighten tensions with China. 

The problem with the U.S. “de–risking” policy is that the existing scope of restrictions on China exceeds the claimed “small yard, high fence” policy.⁷²Particularly because the restrictions cover general technologies, not just ones that have clear military implications, Beijing suspects the U.S. policy is driven by hostile motives to cripple China’s economic growth.⁷³Chinese leaders clearly view the ongoing expanding technological restrictions as a direct threat to vital interests; indeed, this issue appears second only to Taiwan as an area of concern for China.⁷⁴

Therefore, while pursuing “de–risking” in the sense of diversifying trade partnerships and working to reduce Chinese access to selective technologies directly related to advanced military use, the three countries should seek to reassure China about the limited purpose of their trilateral technological supply chain cooperation. While Washington can downscale its restrictions on China to more appropriately meet “small yard, high fence” terms, Tokyo and Seoul can make several credible gestures to signal to Beijing that any cooperation with U.S. technology limitations is intended to support legitimate U.S. national security concerns and not create a broadly exclusionary anti–China economic or technological bloc in the region. 

Insofar as South Korea and Taiwan have applied to join the Comprehensive and Progressive Agreement for Trans–Pacific Partnership (CPTPP), Japan should also welcome China’s application and encourage it to undertake the ambitious reforms necessary to achieve the high standards to qualify for membership. This expansion of the CPTPP, including the joint accession of China and Taiwan, could contribute to peace and stability across the Taiwan Strait.⁷⁵

Japan and South Korea can also work together to regularize the annual Northeast Asian trilateral leadership summit process with China, which has remained on hiatus since 2019 and is reportedly set to resume in the near future.⁷⁶These summits are meaningful in terms of maintaining communications but should also serve as an opportunity to coordinate policies toward North Korea, promote regional economic cooperation including negotiating a trilateral free–trade agreement, and address critical transnational challenges like climate change.⁷⁷

Conclusion: Toward more sustainable trilateral cooperation

In facilitating the Japan–U.S.–South Korea trilateral partnership, President Yoon played a critical role in improving Seoul–Tokyo relations by accommodating Japan’s position on the forced labor issue, which the Japanese euphemistically refer to as “conscripted workers” [chōyōkō]. But U.S. policymakers are concerned about the sustainability of the trilateral partnership because there continues to be widespread criticism in South Korea about Yoon’s compromises toward Japan.⁷⁸

Ideally, Japan and South Korea should use the current improvement in bilateral relations to promote reconciliation at the societal level and develop a shared rather than antagonistic historical perspective. Both countries should deepen and broaden educational, journalistic, and cultural exchanges to examine Japan’s colonial rule over Korea and strive toward a common understanding, or at least one in which there is a great deal of overlap.⁷⁹Japanese and Korean filmmakers and artists could collaborate on projects to enhance accurate public awareness of the past in both countries. Unfortunately, there seems to be little political motivation on both sides to engage in the historical reconciliation task during this goodwill period. Therefore, at a minimum, the two countries, especially Japan, should exercise restraint to avoid provoking nationalistic emotions.⁸⁰

In consolidating and institutionalizing the spirit of Camp David, U.S. policymakers are tempted to rely on an adversarial approach toward China and North Korea. But what would happen if in 2027 South Korea elected a progressive president — who would likely be less tolerant of Japan’s position on historical issues and favor stable relations with North Korea and China? This possibility has become more likely in the wake of South Korea’s recent National Assembly election, which dealt a severe blow to President Yoon and his conservative party.⁸¹As a result, tensions between Seoul and Tokyo could re–emerge and eventually hamper trilateral cooperation.  

Designing the trilateral partnership as a weapon against China and North Korea does not offer a reliable path toward sustainable cooperation. A better way to make the trilateral partnership sustainable and synergetic is to make it compatible with tension reduction, risk mitigation, and constructive engagement with China and North Korea. Such an approach better serves U.S. interests by allowing safer and more productive competition with China. It is also more likely to garner broader public support in both South Korea and Japan beyond the current political alignment between the two countries. 

Regarding maximizing trilateral synergy, U.S. policymakers should also think hard about expanding the theater of cooperation with Japan and South Korea beyond northeast Asia to link the trilateral with U.S. security networks in other regions.⁸² For example, the Biden administration has been seeking to involve South Korea and Japan in arming Ukraine against Russia as well as inviting them to NATO summits.⁸³In this dynamic, both Yoon and Kishida have had to overcome domestic opposition against militarily assisting Ukraine, at the risk of undermining their already weak public support.⁸⁴

Northeast Asia’s security issues involve manifold sensitive and complex questions that often require Japanese and South Korean leaders — especially the latter, who have to deal with sharp domestic divisions on foreign policy issues — to spend significant political capital making difficult choices. Trilateral engagement in multiple regional theaters can magnify security burdens, thereby requiring a greater allocation of political capital and resources. Broadening the geographic scope of the Japan–U.S.–South Korea trilateral may seem attractive at first glance, given Seoul and Tokyo’s interest in enhancing their international role and influence. But such an expansion risks diverting Japan and South Korea’s attention and energy away from the acute security challenges in northeast Asia.

James Park is a research associate at the Quincy Institute’s East Asia Program. His research interests include South Korean foreign policy and domestic politics, Chinese security issues, and U.S. policy vis-à-vis East Asia.

Mike Mochizuki is a non-resident fellow at the Quincy Institute and holds the Japan-U.S. Relations Chair in Memory of Gaston Sigur at the Elliott School of International Affairs in George Washington University. He directs the Elliott School’s undergraduate degree programs…