1. Compound Crises in the Second Trump Administration and the Limits of 'Parallel Development 1.0'

The international order in Northeast Asia has entered an era of 'compound crises,' in which security and economic crises are intertwined and mutually reinforcing. First, North Korea continues to advance its nuclear and missile capabilities and has expanded its military cooperation with Russia. Second, the second Trump administration is demanding that allies shoulder greater responsibility for their own defense and for regional security. Third, following the protracted war in Ukraine, the outbreak in February 2026 of war between the United States and Israel, on the one hand, and Iran, on the other (hereafter 'the Iran War'), has sharply increased instability in supply chains for energy, shipping, critical minerals, and defense goods. Today, military security and economic security can no longer be treated separately.

Against this backdrop, the need for both Korea-US-Japan and Korea-China-Japan cooperation has grown simultaneously. The Korea-US alliance and Korea-US-Japan security cooperation have become all the more important for responding to North Korea's nuclear and missile threats and the expansion of military cooperation between North Korea and Russia. At the same time, responding effectively to the Iran War, instability in the Strait of Hormuz, and energy and supply-chain shocks requires economic security cooperation not only between South Korea and Japan but among the region's major countries, including China. Rather than choosing one of the two trilateral frameworks and weakening the other, it is therefore more realistic to design them so that each performs a different function.

One point should be made clear at the outset. The United States formally maintains its extended deterrence commitments to South Korea and Japan. In the Joint Fact Sheet issued after the November 2025 Korea-US summit, the United States reaffirmed its commitment to provide extended deterrence to the Republic of Korea using the full range of its capabilities, including nuclear, and also expressly committed to strengthening Korea-US-Japan cooperation.¹⁾ The current situation is therefore better understood as one in which US extended deterrence commitments remain in place, while allies' roles and responsibilities, the predictability of actual military operations, and the availability of strategic resources are becoming increasingly important.

The 2026 US National Defense Strategy (NDS) illustrates this very clearly. While prioritizing homeland defense and the deterrence of China in the Indo-Pacific, it calls on allies and partners in Europe, the Middle East, and on the Korean Peninsula to take primary responsibility for their own defense, with the United States providing critical but more limited support. With respect to the Korean Peninsula in particular, the NDS states that, given its powerful military, high defense spending, robust defense industry, and mandatory conscription, "South Korea is capable of taking primary responsibility for deterring North Korea with critical but more limited U.S. support," and that this shift in the balance of responsibility is consistent with America's interest in updating US force posture on the Korean Peninsula. The NDS also highlights the 'simultaneity problem'—the possibility of crises erupting in several regions at once—and urges allies to increase their defense investment and expand their defense-industrial capacity. Notably, although the NDS describes North Korea's nuclear forces as a 'clear and present danger' to the US homeland, it makes no mention whatsoever of North Korea's denuclearization. This does not mean, however, that the US administration has formally abandoned the goal of North Korean denuclearization: the 2025 Korea-US Joint Fact Sheet explicitly reaffirmed the goal of the 'complete denuclearization' of North Korea.²⁾ Even so, the fact that the NDS places deterrence and allied burden-sharing ahead of denuclearization deserves attention as a sign of shifting US strategic priorities. The NDS further states that its goal is not to dominate, strangle, or humiliate China, but to establish a balance of power in the Indo-Pacific that allows all to enjoy a 'decent peace.'³⁾ Taken as a whole, the NDS represents less an abandonment of alliances than an effort to recalibrate the distribution of responsibilities within them. Moreover, since Washington itself seeks a stable relationship with Beijing, there is room for South Korea to pursue strategic communication with China while strengthening Korea-US-Japan cooperation.

Meanwhile, US-China relations have become more stable than a year ago as summit diplomacy resumed in 2026, whereas the chill in China-Japan relations has persisted since Prime Minister Sanae Takaichi's Diet remarks on Taiwan in November 2025. At the US-China summit in Washington in September 2026, President Trump reportedly urged President Xi Jinping to talk with Prime Minister Takaichi, but Xi held to the position that "China-Japan relations and China-US relations are separate matters."⁴⁾ While the stabilization of US-China relations lowers the burden on Seoul of maintaining cooperative channels with Beijing, it also means that South Korea must prepare for the possibility of great-power bargains that do not adequately reflect its interests.

To understand what this paper calls 'Parallel Development 2.0,' it is first necessary to clarify the nature of the existing parallel approach, namely 'Parallel Development 1.0.' 'Parallel Development 1.0' is not a term formally used by past governments or by academia; it is an analytical concept the author uses to describe the existing view that Korea-US-Japan and Korea-China-Japan cooperation should be maintained and developed simultaneously. The essence of 1.0 lay in 'coexistence and compatibility': the two frameworks were not mutually exclusive, and South Korea could pursue both in parallel. Korea-US-Japan cooperation centered mainly on North Korea's nuclear and missile programs and on security issues, while Korea-China-Japan cooperation developed around relatively less sensitive areas such as the economy, trade, culture, and the environment.

In an era of compound crises, however, such simple parallelism is no longer sufficient. Under 1.0, the two frameworks merely divided their domains according to sensitivity without being linked to each other. As a result, Korea-China-Japan cooperation was easily suspended whenever China-Japan tensions or US-China competition intensified, while Korea-US-Japan cooperation risked being perceived as an anti-China bloc. 'Parallel Development 2.0,' as proposed here, goes beyond simply maintaining the two frameworks side by side: it seeks to assign each a more clearly defined function and to link them under the shared goal of stability in Northeast Asia. Korea-US-Japan cooperation would play the central role in deterrence and defense against North Korea's nuclear and missile threats, in intelligence sharing, and in defense-industrial cooperation, while Korea-China-Japan cooperation would strengthen its functions in strategic communication, crisis management, economic security, and supply-chain stability. The core of 2.0 thus lies in a shift from 'the coexistence of the two frameworks' to 'their functional division of labor and mutual complementarity.'

Underpinning this shift are the 'Strategic 3Rs': Responsibility, Resilience, and Recognition. Responsibility is the pillar that strengthens Korea-US-Japan cooperation while reinforcing the defense capabilities of South Korea and Japan; Resilience is the pillar that strengthens the capacity of both Korea-Japan and Korea-China-Japan cooperation to respond to the shocks of war and supply-chain disruption; and Recognition is the pillar that manages the security dilemma through mutual acknowledgment of one another's alliances, strategic standing, and legitimate security concerns. The relationship among the three elements and the specific division of functions are set out in Section 5.

2. North Korea's Nuclear Threat and Expanding North Korea-Russia Military Cooperation: The Structural Need for Korea-US-Japan Cooperation

The most direct driver of stronger Korea-US-Japan cooperation is the advancement of North Korea's nuclear and missile capabilities. As South Korea, the United States, Japan, and many other countries pointed out at a UN Security Council meeting in April 2026, North Korea has continued in 2026 to pursue the qualitative and quantitative expansion of its new strategic assets and nuclear and missile capabilities.⁵⁾ In addition, the Multilateral Sanctions Monitoring Team (MSMT), composed of eleven countries including South Korea, the United States, and Japan, documented illicit North Korea-Russia military cooperation in detail in its first report, and that cooperation has continued since. Particularly noteworthy is the deployment of North Korean troops, weapons, and ammunition in support of Russia's war in Ukraine.⁶⁾ Nor is North Korea-Russia military cooperation merely a one-way relationship in which Pyongyang supplies Moscow with weapons and troops; it also raises the possibility that Russian military technology and operational experience will feed into the enhancement of North Korea's missile, drone, space, and submarine capabilities. In addition, two North Korea-China summits have been held—on the occasions of General Secretary Kim Jong Un's visit to China in September 2025 and General Secretary Xi Jinping's visit to North Korea in June 2026—yet neither of the Chinese Foreign Ministry's official readouts mentioned the 'denuclearization of the Korean Peninsula.' In its November 2025 white paper on arms control, disarmament, and nonproliferation, China also dropped the reference to the 'denuclearization of the Korean Peninsula' that had appeared in its 2005 white paper on the same subject. The fact that North Korea is gaining greater diplomatic and economic room for maneuver through its ties with both Russia and China further heightens the need for Korea-US-Japan cooperation.

Under these circumstances, South Korea's security strategy should firmly maintain the Korea-US alliance and US extended deterrence while further strengthening its own defense capabilities. As North Korea's nuclear forces expand, a posture in which South Korea relies solely on the US nuclear umbrella becomes difficult to sustain, both politically and militarily. Yet it would also be inaccurate to conclude that US extended deterrence has become meaningless. The more precise issue lies not in the US 'commitment' itself, but in its operational implementation and in the 'strategic resources'—weapons, munitions, ships, air power, and supporting capabilities—that the United States can make available in sufficient quantity if several conflicts erupt at once.

In this respect, it is useful to distinguish three dimensions of the credibility of extended deterrence: declaratory credibility, operational credibility, and strategic-resource credibility. 'Declaratory credibility' has been largely sustained through Korea-US summit documents, the Nuclear Consultative Group (NCG), and the Security Consultative Meeting (SCM). 'Operational credibility,' by contrast, is subject to a degree of fluctuation depending on the US president's judgment, the conduct of combined exercises and the deployment of strategic assets, US-North Korea relations, and US domestic politics. 'Strategic-resource credibility' becomes an even more pressing issue when missiles, munitions, and air defense systems are being consumed simultaneously in multiple theaters, as in the Ukraine and Iran wars. What South Korea needs to do, therefore, is not to distrust extended deterrence, but to enhance its effectiveness by strengthening Korea-US nuclear-conventional integration and combined operational planning, as well as South Korea's own conventional deterrence and defense-industrial base.

The second Trump administration's burden-sharing demands can be understood in the same context. If the United States asks South Korea to assume greater defense responsibilities, Seoul need not view this merely as a demand to shoulder more costs. The more South Korea strengthens its capabilities in surveillance and reconnaissance, missile defense, precision strike, naval and air power, cyber and space, and munitions, maintenance, and logistics, the stronger the deterrent posture of the alliance as a whole can become. Expanding its contribution to the alliance can enhance both South Korea's strategic autonomy and its bargaining power.

The expansion of Korea-Japan cooperation should likewise be understood in light of these structural changes. South Korea and Japan are each allied with the United States and are both exposed to North Korea's nuclear and missile threats. The need for the two countries to expand cooperation is growing in areas such as North Korean missile warning data, maritime domain awareness, anti-submarine warfare, cyber defense, and defense supply chains. Korea-Japan cooperation does not, however, imply a Korea-Japan military alliance. Taking into account historical issues, domestic politics, and legal and institutional constraints in both countries, the sustainable course is to build up cooperation step by step, starting with practical areas.

Developing Korea-Japan and Korea-US-Japan security cooperation in a sustainable manner also requires attention to the political instrumentalization of history. China has recently criticized Japan's defense buildup, the expansion of its long-range strike capabilities, and the easing of its arms export restrictions, linking them to 'remilitarization' or 'neo-militarism.'⁷⁾ Squarely confronting the history of Japan's colonial rule and aggression is an important principle of Korean diplomacy, but legitimate grievances about the past must be distinguished from labeling every current Japanese effort to strengthen its defense as a revival of militarism. While managing historical issues with Japan in a principled manner, South Korea should assess historical questions and current security issues separately, each on the basis of facts and international norms, so that history is not used as a means to justify a new bloc confrontation in Northeast Asia.

At the same time, the strengthening of South Korea's and Japan's defense capabilities and their expanding cooperation may be perceived by China and North Korea as a new threat. Long-range precision strike, missile defense, and maritime, space, and cyber capabilities—defensive measures from the standpoint of Seoul and Tokyo—may look like pressure or encirclement to the other side. Conversely, the issue of Chinese structures in the Yellow Sea, about which the South Korean government has raised concerns, and incursions by Chinese and Russian military aircraft into the Korea Air Defense Identification Zone (KADIZ) heighten South Korea's threat perceptions. The security dilemma, in other words, runs in both directions. Mitigating it requires pairing capability development with transparency, crisis communication, the prevention of accidental clashes between naval vessels and military aircraft, and high-level strategic dialogue. This is precisely why stronger Korea-US-Japan cooperation and expanded Korea-China-Japan strategic communication are needed at the same time.

3. The Ukraine and Iran Wars and Economic Security: Korea-Japan Cooperation and Trilateral Resilience among Korea, China, and Japan

The second axis of the compound crisis is economic security. The war in Ukraine demonstrated that energy, grain, and defense production capacity are directly tied to the ability to sustain a war. On top of this, the Iran War, which began in February 2026, has directly shaken energy transport routes through the Strait of Hormuz and the Gulf. In June 2026, the OECD assessed that energy supply disruptions and price increases stemming from the conflict in the Middle East were key factors lowering global growth and raising inflationary pressures. In the first week of October 2026, attacks on tankers in the Strait of Hormuz reached their highest weekly level since the outbreak of the Iran War—a sign of the prolonged instability in international crude oil and refined-product markets.⁸⁾

South Korea and Japan are particularly vulnerable to such shocks. Although both are global manufacturing and trading powers, they rely heavily on overseas sources of energy and key raw materials. According to the Korea Institute for Defense Analyses (KIDA), South Korea and Japan depend on the Middle East for approximately 70% and 94% of their crude oil, respectively, and the South Korean government has stated that about 61% of the country's total crude imports pass through the Strait of Hormuz. China's dependence on Middle Eastern crude, by comparison, is relatively low at about 46.8%.⁹⁾ Although military conflict in the Middle East is far from Seoul and Tokyo, its effects are transmitted directly to both economies through oil and electricity prices, shipping costs, corporate production costs, and export competitiveness. Korea-Japan cooperation is therefore bound to expand beyond the North Korea issue to energy, critical minerals, semiconductors and artificial intelligence (AI), shipbuilding and defense, and the security of sea lines of communication.

Indeed, at the Korea-Japan summit held in Andong on May 19, 2026, the two leaders discussed the situation in the Middle East and supply-chain issues as key agenda items and agreed to hold concrete consultations on crude oil and petroleum product swaps and mutual supply, LNG supply and demand, and strengthening the resilience of energy supply chains.¹⁰⁾ This shows that the expansion of Korea-Japan cooperation cannot be explained entirely through the single lens of countering China. In large part, it stems from the structural need to respond jointly to global economic instability and supply-chain shocks.

Resilience cooperation, however, should not be confined to Korea-US-Japan or Korea-Japan cooperation. South Korea, China, and Japan lie at the heart of East Asia's production networks, and their supply chains are deeply interconnected. At the Ninth Korea-Japan-China Trilateral Summit in 2024, the three countries agreed to expand cooperation in a range of areas, including supply-chain stability, economic cooperation, health, and disaster management.¹¹⁾ Even as competition intensifies, a minimum joint response mechanism is needed in areas such as energy, critical minerals, shipping, semiconductor materials, and pharmaceuticals, where a shock in one country is immediately transmitted to the others.

In practice, however, the situation is far more challenging. The Tenth Korea-Japan-China Trilateral Summit, which Japan as chair has sought to convene since the Ninth Summit in Seoul in May 2024, has been indefinitely delayed by China-Japan tensions, and a number of ministerial- and director-general-level consultative bodies have effectively stalled.¹²⁾ China's use of supply chains as a means of pressure, including rare earth export controls against Japan, also undermines the very premises of trilateral resilience cooperation among Korea, China, and Japan.¹³⁾ Moreover, because China is less dependent on the Strait of Hormuz than South Korea and Japan, its incentives to participate in joint emergency cooperation are relatively weak. Precisely for this reason, however, rather than tying Korea-China-Japan cooperation solely to the top-level format of summits, South Korea can serve as a bridge that revives cooperation starting with 'low politics' agendas, drawing on the Seoul-based Trilateral Cooperation Secretariat (TCS), working-level consultative bodies, and the functional cooperation frameworks of ASEAN Plus Three (ASEAN+3).

Resilience in this sense is not synonymous with 'exiting the Chinese market' or 'decoupling.' Reducing excessive dependence on any particular country or sea lane and diversifying supply sources and production bases is a matter of national risk management. At the same time, maintaining stable trade and production networks with China also serves South Korea's economic interests. Strengthening supply-chain cooperation with the United States and Japan and managing economic cooperation with China in a stable manner are therefore not necessarily contradictory.

It is more realistic for Korea-China-Japan economic security cooperation to begin not with grand integration plans but with mechanisms that can actually function in a crisis: regularly assessing risks to crude oil, LNG, food, critical minerals, and maritime logistics; activating emergency consultations when supply disruptions occur; and sharing early-warning and stockpile information to the extent possible. Such functional cooperation can be sustained even amid political and security tensions. The Chiang Mai Initiative Multilateralization (CMIM) and the ASEAN Plus Three Emergency Rice Reserve (APTERR) are precedents showing that functional emergency cooperation mechanisms can endure despite political tensions in the region. Building a 'floor' for cooperation in normal times is the most realistic way to reduce costs in times of crisis.

4. South Korea as a Strategic Middle Power and China's Perspective: The Conditions for 'Recognition'

In an era of compound crises, South Korea's national power and strategic standing also need to be reassessed. Today's South Korea can no longer be described simply as a passive middle power forced to choose between the United States and China. It possesses substantial conventional military power; production capacity in strategic industries such as shipbuilding, semiconductors, batteries, nuclear power, automobiles, and defense; and a multilayered international network linking the United States, Japan, Europe, ASEAN, India, and the Middle East.

According to the Stockholm International Peace Research Institute (SIPRI), South Korea emerged as the world's ninth-largest exporter of major arms in 2021–2025 and, over the same period, accounted for 8.6% of arms imports by European NATO member states, making it the second-largest supplier after the United States.¹⁴⁾ The United States, too, is actively drawing on South Korea's capital, production capacity, and technology as it seeks to strengthen its shipbuilding industry and its semiconductor and critical-mineral supply chains. The November 2025 Korea-US Joint Fact Sheet identified the modernization of the US shipbuilding industry, the maintenance, repair, and overhaul (MRO) of naval vessels, workforce development, and supply-chain cooperation as key areas of cooperation. Notably, in the same document the United States approved South Korea's construction of nuclear-powered submarines and supported the process that will lead to the ROK's civil uranium enrichment and spent fuel reprocessing for peaceful uses.¹⁵⁾ This can be seen as an instance in which the United States institutionally 'recognized' South Korea's expanded role and strategic standing within the alliance.

The author characterizes such a South Korea as a 'strategic middle power.' A strategic middle power is a state that, while falling short of superpower or great-power status, possesses military power capable of influencing its surrounding security environment, strategic industries and core technologies that even great powers need, a multilayered diplomatic and security network, and the capacity to make a degree of independent strategic choice in pursuit of its national interests. Strategic autonomy in this sense does not mean distancing oneself from one's alliance. Rather, it means widening one's range of options by expanding one's own capabilities and cooperative networks while maintaining the alliance. The author's proposed 'Security Cooperation Framework of Five Strategic Middle Powers (SMP5)'—South Korea, Japan, France, the United Kingdom, and Germany—likewise stems from the conviction that, amid uncertainty over extended deterrence, strategic middle powers should act as active architects of the regional security architecture.¹⁶⁾

China's policy toward South Korea also needs to reflect these changes. If China views South Korea solely through the lens of its status as a US ally, it will struggle to understand Seoul's policy decisions accurately. South Korea's foreign policy is shaped not only by the Korea-US alliance but also by the North Korean threat, domestic politics, Korea-Japan relations, industrial and technological interests, and its networks with Europe, Asia, and the Middle East. At the Korea-China summit held during President Lee Jae Myung's state visit to China in January 2026, the two countries reaffirmed the 'Korea-China Strategic Cooperative Partnership' as an important diplomatic asset and confirmed their intention to put the relationship on a track of stability and development.¹⁷⁾

How, then, does China view the two trilateral frameworks? China perceives them in starkly different ways. Immediately after the Korea-US-Japan summit at Camp David in August 2023, the Chinese Foreign Ministry expressed "strong dissatisfaction and firm opposition," arguing that the Asia-Pacific must not become an arena for great-power rivalry and that bloc confrontation must not be replicated in the region. The fact that China's response focused not on North Korea but on Taiwan and the South China Sea shows that Beijing effectively regards Korea-US-Japan cooperation as an alignment aimed at checking China.¹⁸⁾

By contrast, China seeks to use Korea-China-Japan cooperation as a framework centered on the economy and trade. At the May 2024 summit in Seoul, Premier Li Qiang voiced opposition to protectionism, decoupling, and the severing of supply chains, and stressed that economic and trade issues should not be politicized or securitized.¹⁹⁾ This reflects an intention to keep Korea-US-Japan economic security cooperation from leading to China's exclusion. At the same time, China has repeatedly halted trilateral cooperation whenever bilateral disputes have arisen, as it did after the 2012 Senkaku dispute, the 2016 THAAD deployment, and Prime Minister Takaichi's 2025 remarks on Taiwan.²⁰⁾ For China, Korea-China-Japan cooperation is less an institutionalized principle than a lever for managing its relations with Japan and South Korea.

China's receptiveness to 'Parallel Development 2.0' therefore varies by domain. Economic security and supply-chain cooperation are relatively likely to be acceptable, since it accords with the 'supply-chain stability' that China itself has emphasized. Indeed, at the 13th Korea-Japan-China Economic and Trade Ministers' Meeting held in Seoul in March 2025, the three countries agreed to strengthen supply-chain cooperation and to continue discussions on accelerating negotiations for a Korea-Japan-China FTA.²¹⁾ Security agendas such as a strategic stability dialogue, by contrast, will be harder for China to accept, as Beijing is likely to link them to Korea-US-Japan cooperation or to the Taiwan issue. Ultimately, the biggest obstacle to China's participation is its 'linkage strategy' of tying trilateral cooperation to bilateral disputes. Mitigating this requires three things. The first is an interest-based approach that puts on the agenda priorities China itself has emphasized, such as opposition to decoupling and support for supply-chain stability. The second is to start with working-level and functional cooperation that carries a lighter political burden than summits. The third is to make clear that the purpose of Korea-US-Japan cooperation is to deal with North Korea, thereby reducing China's grounds for rejecting such cooperation. At the same time, resilience cooperation should be designed as an 'open architecture' that does not make China's participation a precondition, but begins with South Korea and Japan at its core while keeping the door open to China. Only then will China's non-participation be unable to paralyze cooperation as a whole; instead, China itself will increasingly bear the costs of staying out.

If China wants South Korea to exercise strategic autonomy, it must also accept the Korea-US alliance and South Korea's own security concerns as realities. A starting point could be for China to resolve constructively, on the basis of mutual respect, the issue of the Yellow Sea structures about which the South Korean government has raised concerns, and to maintain a responsible position on the North Korean nuclear issue and the UN Security Council sanctions regime against North Korea. Conversely, South Korea also needs to understand why China is concerned about US military deployments and Korea-US-Japan security cooperation. 'Recognition' here does not mean accepting the other side's claims or making concessions. It means acknowledging that the other side, too, is an actor with its own interests and threat perceptions, and keeping those differences within manageable bounds.

In this regard, a 'Recognition Paradox' may arise. The more China, wary of the expansion of Korea-US-Japan cooperation, treats South Korea and Japan merely as dependent variables of US strategy and refuses to recognize their own security concerns, the more likely the two countries are to draw even closer to the United States. Conversely, if China treats South Korea and Japan as independent strategic actors and expands substantive interests and channels for cooperation with them, it can reduce the incentives for Korea-US-Japan cooperation to evolve automatically into an anti-China bloc across all domains.

From South Korea's perspective, cooperation with China is not intended to replace the Korea-US alliance or its strategic partnership with the United States. China is a great power adjacent to the Korean Peninsula and a nuclear-weapon state that wields enormous influence over the stability of the Yellow Sea, the East China Sea, and the Taiwan Strait, as well as over regional supply chains. South Korea should uphold both the principles of the Korea-US alliance and pragmatic cooperation with China, while distinguishing between issues that call for security vigilance and those that allow for cooperation. This is a realist approach befitting a strategic middle power.

5. 'Parallel Development 2.0' and the Strategic 3Rs: A Functional Redesign of the Two Trilateral Frameworks

Taken together, the preceding discussion suggests that South Korea's policy in an era of compound crises cannot realistically be designed around an either-or choice between Korea-US-Japan and Korea-China-Japan cooperation. Direct security threats—North Korea's nuclear weapons and missiles and North Korea-Russia military cooperation—must be addressed through the Korea-US alliance and Korea-US-Japan cooperation. At the same time, the risks of war and supply-chain shocks, military miscalculation, and regional bloc formation must be managed through cooperation with neighboring countries, including China. The reason is that the two frameworks are designed to perform different functions.

This division of functions between the two trilateral frameworks can be summarized in terms of the Strategic 3Rs, as shown in the table below.

The three Rs differ in sequence and function. 'Responsibility' is the foundation for deterrence and defense; 'Resilience' is a buffer that keeps military and economic shocks from spreading; and 'Recognition' is a political-diplomatic stabilizing mechanism that helps prevent crises from escalating by reducing the tendency to interpret the other side's actions solely through worst-case assumptions. If Responsibility alone is strengthened, arms races and bloc formation may intensify; when Resilience and Recognition are combined with Responsibility, stronger national defense capabilities and regional stability can be pursued simultaneously. Emphasizing cooperation with China or Korea-China-Japan cooperation therefore does not weaken South Korea's deterrence or its own defense capabilities. On the contrary, crisis management and cooperation can be pursued more stably when adequate deterrence and national defense capabilities are in place. Nor is Recognition something demanded of China alone. US support for South Korea's construction of nuclear-powered submarines and for the process leading to civil uranium enrichment and spent fuel reprocessing is a case of recognizing South Korea's expanded role within the alliance; between South Korea and Japan, too, mutual recognition on historical issues will determine the sustainability of cooperation.

The first policy task is to continuously strengthen the Korea-US alliance and the effectiveness of extended deterrence. South Korea should further strengthen the Korea-US Nuclear Consultative Group and the combined defense posture, and strengthen its conventional deterrence, defense production capacity, and missile defense, surveillance and reconnaissance, cyber, and space capabilities. Given that the NDS explicitly identifies South Korea as bearing 'primary responsibility' for deterring North Korea, rather than responding passively to the second Trump administration's burden-sharing demands, South Korea needs to redesign the alliance's division of roles by clearly distinguishing between the areas it can take on and those in which US support remains indispensable.

Second, Korea-Japan and Korea-US-Japan cooperation should be developed sustainably, beginning with the areas directly required to counter North Korea's nuclear and missile threats. While strengthening intelligence sharing, missile warning, maritime security, cyber, defense supply chains, and combined and coordinated response mechanisms, Seoul should manage the scope and pace of cooperation realistically, taking into account public acceptance in South Korea and the historical issues between South Korea and Japan. It should be made clear that the purpose of Korea-US-Japan cooperation is not confrontation with any particular country per se, but deterring North Korea's nuclear threat and preserving regional stability.

Third, a 'strategic stability dialogue' should be institutionalized at the Korea-China-Japan level. A formal channel should be established for senior foreign affairs and security officials to discuss North Korea's nuclear and missile programs, large-scale military exercises, accidental clashes at sea and in the air, and emergency communication in times of crisis. Rather than waiting for summits to resume, however, it would be realistic to start with director-general-level consultations among the three countries' foreign and security authorities and to link them with existing bilateral channels such as the Korea-China 2+2 Diplomatic and Security Dialogue and the Japan-China Maritime and Aerial Communication Mechanism. With dialogue between the Chinese and Japanese leaders blocked, South Korea can act as the initiator and coordinator of such a dialogue. Although the three countries cannot agree on every security issue, the deeper their differences, the greater the need for a standing mechanism for crisis-management dialogue.

Fourth, emergency cooperation on economic security and supply chains should be institutionalized. Risks to crude oil, LNG, critical minerals, food, semiconductor materials, and maritime logistics should be assessed regularly, and it should be possible to activate emergency consultation procedures in the event of war in a particular region or the blockade of a major sea lane. Taking as a starting point the crude oil and petroleum product swaps and LNG cooperation that South Korea and Japan have identified as areas of cooperation, consideration could be given to gradually expanding this cooperation to the Korea-China-Japan or ASEAN+3 level by keeping participation open to willing countries. Korea-China-Japan cooperation should be designed not to increase dependence on China but as a mechanism for managing the risks of the interdependence that already exists.

Fifth, on the North Korean nuclear issue, realistic risk reduction needs to be pursued. North Korea reaffirmed its line of strengthening its nuclear forces at the Ninth Congress of the Workers' Party of Korea in February 2026 and has since continued to formally reaffirm its commitment to further strengthening its nuclear forces. Clinging to the goal of North Korea's 'complete denuclearization' must therefore not become a reason to leave the unlimited expansion of its nuclear warheads, fissile material, and delivery systems unchecked. Step-by-step measures should be sought to reduce the risks of nuclear testing, fissile material production, military miscalculation, and accidental clashes. In preparation for the possibility that risk reduction and arms control will emerge on the agenda if US-North Korea dialogue resumes, Seoul needs to establish in advance the position it will convey to Washington. China, too, if it is concerned about the expansion of Korea-US-Japan security cooperation, should take note of the structural chain reaction by which continued growth in North Korea's nuclear capabilities would further accelerate defense buildups in South Korea and Japan and deepen Korea-US-Japan cooperation.

Finally, for 'Parallel Development 2.0' to endure, it requires institutional continuity, reciprocity, and an open agenda. Cooperation that works only when relations between leaders are good is easily suspended when governments change or diplomatic disputes erupt. Mechanisms that operate on a recurring basis—such as high-level strategic dialogues, working-level consultative bodies, and crisis hotlines—must be put in place. At the same time, rather than accommodating every demand of the other side, the scope and limits of cooperation should be clearly defined on the principles of reciprocity and transparency.

Ultimately, peace and stability in Northeast Asia in an era of compound crises cannot be secured through an either-or choice between Korea-US-Japan and Korea-China-Japan cooperation. For South Korea, the Korea-US alliance, US extended deterrence, and Korea-US-Japan cooperation are the core security pillars for responding to North Korea's nuclear and missile threats. Korea-China-Japan cooperation does not replace them—it is a complementary stabilizing mechanism for mitigating economic security shocks, military miscalculation, and unnecessary bloc formation. The essence of 'Parallel Development 2.0' lies in using the Strategic 3Rs—Responsibility, Resilience, and Recognition—to ensure that the two trilateral frameworks perform different functions. By actively designing such a multilayered architecture of cooperation, South Korea should move beyond the role of a passive beneficiary and become an active architect of the Northeast Asian order.

1. The White House, "Joint Fact Sheet on President Donald J. Trump's Meeting with President Lee Jae Myung," November 13, 2025.
2. The White House, "Joint Fact Sheet on President Donald J. Trump's Meeting with President Lee Jae Myung," op. cit.
3. U.S. Department of War, 2026 National Defense Strategy, January 2026, pp. 4, 10, 12–14, 18–21.
4. Park Eun-ha, "[In-Depth News] Xi Jinping Rejects Trump's Urging to 'Talk with Takaichi': Why a China-Japan Summit at APEC Will Be Difficult," Kyunghyang Shinmun, October 8, 2026 (in Korean).
5. United Nations Security Council, S/PV.10147, Non-proliferation/Democratic People's Republic of Korea, April 30, 2026.
6. Multilateral Sanctions Monitoring Team (MSMT), "Violations and Evasions of UN Sanctions on the DPRK through Military Cooperation between the DPRK and Russia," May 29, 2025.
7. Ministry of Foreign Affairs of the People's Republic of China, "Foreign Ministry Spokesperson Mao Ning's Regular Press Conference on April 7, 2026"; "Foreign Ministry Spokesperson Guo Jiakun's Regular Press Conference on September 2, 2026."
8. OECD, OECD Economic Outlook, Volume 2026 Issue 1: Under Pressure, June 3, 2026; Jeong In-gyun, "Attacks on Tankers in Hormuz at 'Highest Since the War Began': 12 Incidents in One Week," Dailian, October 9, 2026 (in Korean).
9. Shin Da-wit, "Economic Security and Defense (IV): The US-Iran War and Energy Security," KIDA Security Strategy FOCUS, No. 26-33, April 28, 2026 (in Korean); "Kang Hoon-sik Departs for Kazakhstan, Oman, and Saudi Arabia to Secure Crude Oil and Naphtha," Newsis, April 7, 2026 (in Korean).
10. Ministry of Trade, Industry and Resources of the Republic of Korea, "Joint Press Release by the Ministry of Trade, Industry and Resources of the Republic of Korea and the Ministry of Economy, Trade and Industry of Japan on Strengthening Cooperation on Energy Security and Supply Chain Resilience," May 19, 2026 (in Korean); Ministry of Foreign Affairs of the Republic of Korea, "Korea-Japan Summit," May 20, 2026 (in Korean).
11. Ministry of Foreign Affairs of the Republic of Korea, "Joint Declaration of the Ninth Trilateral Summit among the Republic of Korea, Japan, and the People's Republic of China," May 27, 2024.
12. Jeong Seong-jo, "China Formally Confirms Korea-China-Japan Summit Will Not Take Place, Citing 'Japanese Prime Minister's Erroneous Remarks,'" Yonhap News Agency, November 24, 2025 (in Korean).
13. Kwon Su-hyun, "China Suspends Review of Rare Earth Export Licenses for Japan, Applying Across All Industries," Yonhap News Agency, January 9, 2026 (in Korean).
14. SIPRI, Trends in International Arms Transfers, 2025, March 2026, pp. 2, 7, 11; SIPRI, "Global arms flows jump nearly 10 per cent as European demand soars," March 9, 2026.
15. The White House, "Joint Fact Sheet on President Donald J. Trump's Meeting with President Lee Jae Myung," op. cit.
16. See CHEONG Seong-Chang, "Chapter 65. A Security Cooperation Framework of Five Strategic Middle Powers (SMP5) in an Era of Uncertain Extended Deterrence: From Passive Beneficiaries to Active Architects of the Security Architecture," in Korea Nuclear Security Strategy Forum, ed., Korea's Nuclear Security Project 6: Energy Security and Nuclear Latency (Seoul: Blue & Note, 2026), pp. 365–396 (in Korean).
17. Ministry of Foreign Affairs of the Republic of Korea, "Toward a New 30 Years with China, an 'Inseparable Cooperative Partner,'" January 7, 2026 (in Korean).
18. Ministry of Foreign Affairs of the People's Republic of China, "Foreign Ministry Spokesperson Wang Wenbin's Regular Press Conference on August 21, 2023"; China Daily (Hong Kong), August 22, 2023.
19. Al Jazeera, "China urges South Korea, Japan to uphold free trade at three-way summit," May 27, 2024.
20. Muhui Zhang, "Northeast Asia's trilateral framework has hollowed out," East Asia Forum, August 14, 2026.
21. Ministry of Trade, Industry and Energy of the Republic of Korea, "Joint Statement of the 13th Korea-Japan-China Economic and Trade Ministers Meeting," March 30, 2025 (in Korean).

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