1. Introduction

The strategic competition between China and the United States presents a new opportunity for the development of China-Japan-South Korea relations. As countries that are geographically proximate and share similar geopolitical perceptions, China, Japan, and South Korea have, over the past two decades, continuously strengthened mutual trust, deepened cooperation, and pursued joint development. “Over the past 20 years, the three countries have established 21 ministerial-level meetings and more than 70 dialogue mechanisms, which have become the main platforms for deepening trilateral cooperation. Their trade volume increased from USD 130 billion in 1999 to over USD 720 billion in 2018, while their combined share of the global economy rose from 17% to 24%. Trilateral cooperation has played an important role in promoting regional and global economic growth and in advancing regional integration.” [1] The China–US “G2” model not only profoundly affects the global political landscape but also deeply influences the Northeast Asian security complex, the forefront of the two countries’ strategic interactions. At the same time, the development of China–Japan–South Korea relations is significantly shaped by the US alliance factor, changes in China–US relations, and broader regional and international dynamics. The closeness or distance of the Japan–US and South Korea–US alliances profoundly impacts the relationships of Japan and South Korea with China. Specifically, Japan and South Korea serve as important strategic anchors and political allies of the United States in Northeast Asia. The US factor is a decisive external element in the development of the “new trilateral” relations, and under the context of China–US strategic competition, “the overall framework of the evolution of China–US relations reshapes the triangular structure of China, Japan, and South Korea in the region (Northeast Asia).” [2]

2. Development of China–Japan–South Korea relations: new dynamics and trends

2.1. China–Japan: cooling Japan–US relations provide opportunities for accelerated rapprochement

China and Japan are neighboring countries “separated only by a strip of water,” sharing thousands of years of civilizational exchange. Chinese civilization has had a profound influence on the development of Japanese civilization. During the height of China’s Sui and Tang dynasties, Japan dispatched large-scale missions—such as the Kenzuishi (Sui missions) and Kentōshi (Tang missions)—to China for cultural and scholarly exchanges [3]. Likewise, China sent prominent Buddhist monks, such as Jianzhen, who braved hardships to propagate Buddhist thought in Japan. Despite this long history of friendly interaction, the historical legacy of Japan’s colonial and military aggression against China since the Meiji Restoration of 1868—which promoted policies of “enrich the country, strengthen the military” and continental expansion—has created a profound psychological and trust gap between the two peoples and nations. After World War II, Japan was occupied solely by the United States under the Allied framework. With the intensification of the Cold War, Japan’s democratization reforms increasingly aligned with US national interests. The 1951 San Francisco Peace Treaty, the US–Japan Security Treaty, and the 1952 US–Japan Administrative Agreement gradually laid the foundation for the US–Japan alliance. Over nearly seventy years, the US has exerted pervasive influence on Japan’s domestic and foreign policies. From the early postwar period, when Japan relied heavily on US support, to the present, when Japan plays a significant role in Northeast Asia and globally, the US–Japan alliance has remained Japan’s fundamental framework for action, and Japan continues to follow US-led norms in major international political agendas. The existence of this alliance has long constrained deeper cooperation between China and Japan. From the early Cold War period, when the US leveraged Japan to form a crescent-shaped encirclement of China, to the Trump administration’s Indo-Pacific strategy aligning with Japan’s “Free and Open Indo-Pacific” vision, Japan has consistently served as a strategic bridge for US containment of China. Additionally, unresolved disputes such as the Diaoyu/Senkaku Islands issue, historical textbook controversies, the Guanghua dormitory incident, East China Sea oil and maritime delimitation disputes, and the Yasukuni Shrine issue have long complicated bilateral relations. The 1972 diplomatic breakthrough during President Richard Nixon’s visit to China brought a turning point in China–Japan relations. In 1972, the two countries signed the Joint Communiqué of the Government of Japan and the Government of the People’s Republic of China, establishing diplomatic relations. In 1978, the China–Japan Peace and Friendship Treaty was concluded, consolidating the achievements of normalization.

In contemporary times, the direct impetus for China–Japan normalization has been the improvement in China–US relations. The US factor remains pivotal in the development of China–Japan relations. Proximity, a long history of turbulence, and the deep influence of the US in trilateral dynamics make China–Japan relations complex and volatile. Since World War II, China–Japan relations can be broadly divided into three phases, each with distinct characteristics: the pre-normalization period (1949–1972), characterized by the absence of diplomatic relations; the post-normalization period (1972–late 1980s), marked by flourishing ties driven by Japan’s economic strength and China’s reform and opening-up policies; and the third phase, beginning with the end of the Cold War, China’s rise, and Japan’s relative decline, in which political, economic, and military confrontation became recurring themes in bilateral literature [4]. Currently, China–Japan relations are at a new starting point. Although traditional areas of dispute remain, Japan—long a staunch US ally in the Asia-Pacific—has gradually warmed its relations with China. Under Trump’s “America First” policy, protectionist and unilateral trade measures were extended even to allies such as Japan, directly cooling Japan–US relations. Despite general alignment with the US in political positions and integrated land, sea, and air defense strategies, Japan has long been a competitor with the US in international trade since its post-1960s economic recovery, a deeper reason for the sustained cooling of Japan–US relations. At the same time, Japan has sought to ease tensions with China and address domestic economic slowdown by pursuing cooperation in broader areas. “Since Shinzo Abe became Prime Minister in September 2006, China–Japan relations have gradually improved. Abe’s visit to China in October 2006, followed by exchanges with Chinese Premier Wen Jiabao in April 2007 and President Hu Jintao in May 2008, further thawed bilateral ties under a framework of 'mutually beneficial relations on the basis of a comprehensive strategic relationship.’ Numerous other developments indicate that the positive trend in bilateral relations continues.” [5] After reaching a low point in 2012 over the Diaoyu/Senkaku Islands dispute, bilateral relations gradually stabilized. External pressures from Trump’s trade policies toward China and Japan further pushed the two countries closer. Since Abe’s last visit to the Yasukuni Shrine at the end of 2013, he has refrained from further visits (as of July 8, 2022), signaling goodwill toward China—forming a basis and prelude for the current warming of relations. Between September and October 2013, China proposed the Belt and Road Initiative (BRI), a strategy with both political and economic dimensions. While primarily intended to supplement and reform the Western-led political-economic order after the global financial crisis, it has often been interpreted by Western countries as “neo-colonial” or a “new Marshall Plan.” As a US ally, Japan’s response to the BRI has not been particularly strong. However, the Abe government sent representatives to both the May 2017 and April 2019 Belt and Road Forum for International Cooperation in Beijing, signaling Japan’s goodwill. Moreover, Japan’s Indo-Pacific strategy identifies three pillars for achieving a “Free and Open Indo-Pacific”: promoting the rule of law, freedom of navigation, and free trade; pursuing economic prosperity; and committing to peace and stability [6]. Japan’s official statements indicate that its Indo-Pacific vision has many points of convergence with China’s BRI, suggesting broad areas of potential cooperation and overlapping interests in Northeast Asia.

Compared with China–South Korea relations, which have been heavily affected by the deployment of the THAAD missile defense system and the North Korean nuclear issue, China–Japan relations have continued to “advance to new levels.” “2018 marked the 40th anniversary of the signing of the China–Japan Peace and Friendship Treaty, symbolizing that bilateral relations had entered a new and broader phase… Overall, the frozen relationship had begun to thaw.” [7] Thus, 2018 was an exceptionally important year since the normalization of diplomatic relations between China and Japan, representing a key step toward returning bilateral relations to a normal track and creating a new historical starting point. As the world’s second-largest economy, China is an important economic and trade partner for Japan. The two countries share close economic ties and strong complementarity, a structural reality that helps explain why China–Japan relations frequently experience “political cooling” but rarely “economic cooling.” Since President Trump took office, the relative decline of the United States and its strategic retrenchment led Japan to lose confidence in defense cooperation with the US, creating a pressing need for balance in its defense and security posture. This, in turn, became an important external condition favoring the warming of China–Japan relations. In short, it is the shared influence of the US factor that has gradually drawn China and Japan closer together. In June 2019, China and Japan jointly proposed a “Ten-Point Consensus” to guide bilateral relations [8]. At the Eighth Trilateral Summit in December 2019, the two countries reached a strategic consensus on three new principles to guide bilateral relations: “mutual cooperation,” “non-threat to each other,” and “transforming competition into coordination,” establishing a normative framework for future development.[9–10] Faced with the realistic opportunity for China–Japan relations to reach a new stage, future development should guard against “information asymmetry” caused by selective media reporting, adhere to the four political documents agreed upon by the two countries, cultivate and expand friendly cooperative groups, and strengthen people-to-people and cultural exchanges. For contentious historical issues, such as disputes in the East China Sea, initial focus can be placed on non-traditional security matters and lower-level political issues, such as joint resource development, marine resource protection, and prevention of maritime pollution, through preliminary discussions and negotiations. In summary, “China–Japan relations are both complex and special; they cannot be expected to always be smooth. Both sides should approach bilateral relations with a long-term vision and broad-mindedness, handle issues rationally and pragmatically, without being swayed by emotions or constrained by temporarily unsolved problems. Only in this way can China–Japan relations be advanced to a new stage, enhance the well-being of the peoples of both countries, and contribute to global peace and development.” [11]

2.2. China–South Korea: preliminary resolution of the THAAD issue provides a “window period” for returning bilateral relations to normal

The relationship between China and South Korea can be traced back to thousands of years of civilizational exchange between the central Chinese dynasties and the states of the Korean Peninsula, with officially recorded interactions beginning during the Han Dynasty’s exchanges with the Three Han (Mahan, Jinhan, and Byeonhan). Although official and popular contacts experienced intermittent disruptions thereafter, they were never fully severed. During the 14th century, under the Joseon Dynasty in Korea and the Ming Dynasty in China, political and economic ties became increasingly close. In modern times, the rise of Japan following the Meiji Restoration, driven by the needs of capitalist development, led to increased infiltration and aggression toward the Korean Peninsula. “In February 1876, the two sides signed the Treaty of Ganghwa, also known as the Treaty of Amity between Korea and Japan… Thereafter, Japan and Western powers continued to deepen their aggression in Korea.” [12] Following the Russo-Japanese War, Japan gradually strengthened its penetration of Korea, culminating in the full annexation of Korea in 1910, placing it under Japanese colonial rule and stripping it of its status as an independent sovereign state. Official relations between China and Korea were also gradually interrupted. In modern times, official China–South Korea interactions resumed with the establishment of the Provisional Government of the Republic of Korea following the March 1st Movement in 1919. In November 1921, Syeon Gu-i, acting Prime Minister of the Korean Provisional Government, established diplomatic relations with the Nationalist Government in Guangzhou, marking the origin of contemporary China–South Korea diplomatic ties. After the victory in the Anti-Fascist War in 1945, the Korean Peninsula was liberated. However, due to secret agreements such as the Yalta Conference, the outbreak of the Cold War, and the confrontation between the US and Soviet blocs, the peninsula was divided into two states. Owing to the impact of the Korean War, ideological differences and social system disparities between China and South Korea, the “special relationship” between China and North Korea, and the US–South Korea alliance, China–South Korea relations remained largely stagnant. With the end of the Cold War, changes in the international situation, shifts in global themes, and proactive efforts by both countries, China and South Korea issued the China–South Korea Joint Communiqué in 1992, formally establishing diplomatic relations. “The two countries’ friendly and cooperative relations have rapidly developed across various fields. Politically, the leaders frequently visit each other or meet in multilateral international forums, enhancing mutual understanding and trust, and promoting the development of bilateral relations. Economically, mutually beneficial cooperation has deepened, with each country serving as an important trading partner; exchanges and cooperation in culture, education, and science and technology have become increasingly active. The two countries maintain close coordination and cooperation on regional and international affairs.” [13] Despite the fruitful results over the 28 years since normalization, significant conflicts persist in four main areas: Economic and historical disputes: Between 1999 and 2000, the two countries experienced trade disputes over garlic products. In 2004, disagreements arose regarding the historical legitimacy of the ancient Goguryeo kingdom on the Korean Peninsula. National security: Following the March 2010 Cheonan incident and the November 2010 shelling of Yeonpyeong Island, South Korea perceived China’s handling of the events as favoring North Korea, causing rifts in bilateral relations. THAAD deployment: South Korea’s decision to deploy the THAAD missile defense system, despite China’s security concerns, led China–South Korea relations to reach the lowest point since normalization. Third-party involvement: Both security incidents involved external actors, including the US and North Korea, which amplified and prolonged their impact. Fundamentally, the obstacles to healthy and stable China–South Korea relations stem from the North Korean nuclear issue and the existence of the US–South Korea alliance.

To some extent, while bilateral economic relations have generally risen steadily, the intersection of the US–South Korea alliance and the North Korean nuclear issue has become a major factor hindering China–South Korea relations. The origins of the North Korean nuclear issue lie in the security threats posed to North Korea by the United States and South Korea, including potential war. North Korea’s nuclear program has a long history: “Since the 1950s, with Soviet assistance, North Korea began developing its nuclear program… As North Korea’s nuclear capabilities grew, US attention to its nuclear program intensified.” [14] After the Korean War, to contain communism and mitigate the growing nuclear threat to South Korea and Japan, the United States and South Korea signed the US–South Korea Mutual Defense Treaty, gradually establishing a formal alliance. Although the Korean War ended with the signing of the Armistice Agreement in July 1953, this represented only a temporary ceasefire rather than a permanent end to the war. This incomplete resolution motivated North Korea to develop nuclear weapons as a means of self-preservation. By the 1980s, North Korea’s nuclear facilities had reached a certain scale, with the most important located in Yongbyon in the northeast of the country. Although North Korea joined the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) in 1985, it maintained a resistant and semi-transparent stance toward IAEA inspections. North Korea continued clandestine nuclear weapons development, which the United States and South Korea, seeking to maintain the nuclear balance in Northeast Asia, could not accept. Between 2003 and 2007, six rounds of the Six-Party Talks were held, but negotiations were arduous and ultimately failed to produce a final resolution. North Korea subsequently announced an indefinite withdrawal from the talks. Between October 2006 and September 2017, North Korea conducted six nuclear tests, each increasing in power and intensity, drawing significant international concern.

Fearing the threat posed by North Korea’s nuclear and missile programs, and within the framework of the US–South Korea alliance as well as the broader context of China–US strategic competition, “the two countries signed an agreement in July 2016 to deploy the THAAD system, which was scheduled to achieve full operational capability by the end of 2017. This is a US-style missile defense system, designed to intercept short- and medium-range ballistic missiles in the terminal phase if Seoul continues to face threats from Pyongyang.” [15] Because the THAAD system possesses both defensive and offensive capabilities, its deployment introduced new risk points into the already volatile security environment of Northeast Asia. Rather than reducing crises, it intensified the region’s “security dilemma.” Its radar coverage includes China’s northern territory, particularly most of Northeast China, giving it surveillance capabilities over Chinese territory. China strongly opposed the deployment, and bilateral relations between China and South Korea quickly plunged to their lowest point since normalization. In response to China’s strong opposition, broad unofficial economic resistance, the escalation of the China–US trade war, and South Korea’s desire for China to play a greater role in resolving the North Korean nuclear issue, the two countries initiated negotiations over the THAAD issue. “In October 2017, China and South Korea reached a basic consensus on resolving the THAAD issue and removing obstacles in bilateral relations. South Korea pledged not to deploy additional THAAD systems, not to join the US missile defense network, and not to develop a US–South Korea–Japan trilateral military alliance, while stating it had no intention of harming China’s security interests. On this basis, China–South Korea relations began to improve.” [16] The North Korean nuclear issue saw a temporary thaw in February 2018, coinciding with the PyeongChang Winter Olympics, when China, the US, South Korea, and Japan engaged in positive interactions around the Korean Peninsula, creating a brief period of hope. However, by the end of 2019, efforts to achieve a comprehensive peace and denuclearization agreement failed, and US–North Korea negotiations stalled. South Korea, constrained by a lack of initiative in its North Korea policy and adherence to the US–South Korea alliance framework, missed opportunities to improve inter-Korean relations, and relations between North and South Korea fell into another low.

China and South Korea, as key countries in Northeast Asia, face the United States attempting to leverage its alliance with South Korea to escalate its strategy of containing China. From the Cold War-era “crescent-shaped encirclement” of China to the present-day push for South Korea to join the US “Indo-Pacific Strategy” and serve as a key pillar of that strategy in Northeast Asia, this reflects Washington’s strategic objective. In practice, expecting South Korea to act as the vanguard of US containment of China is currently neither feasible nor necessarily desirable, and could even undermine the stability of the US–South Korea alliance. “Traditional views hold that South Korea will eventually have to choose a complete political alignment with either China or the US. However, within the framework of great-power tensions, South Korea continues to demonstrate a tendency to adopt an independent stance in its relations with China.” [17] From a geopolitical perspective, China is South Korea’s largest trading partner, the China–North Korea Treaty of Friendship, Cooperation, and Mutual Assistance remains in effect, and South Korea hopes that China can play an important role in fundamentally resolving the North Korean nuclear issue. Against the backdrop of China–US strategic competition, South Korea seeks to achieve a political balance between the two powers. After President Moon Jae-in’s visit to China in 2018, China–South Korea relations gradually improved. At the December 2019 Trilateral Summit, China sought to continue “linking the Belt and Road Initiative with South Korea’s New Southern and New Northern Policies,” and both countries reached consensus on issues including “jointly building a community with a shared future for mankind,” the situation on the Korean Peninsula, and the promotion of free trade [18]. Furthermore, “the easing of China–South Korea bilateral relations should be viewed in the context of rising protectionism, unilateralism, and anti-globalization trends.” [16] Although the first phase of the China–US trade agreement was reached in January 2020, nearly two years of trade friction had already severely affected South Korea’s export-oriented economy, creating an urgent incentive for South Korea to repair its relations with China and further expand exports to China. In summary, the current restoration of China–South Korea relations aligns with the shared interests of both countries.

2.3. Japan–South Korea: historical and contemporary issues intertwined, bilateral relations exhibit a “pendulum effect”

Civilizational exchanges and interactions between Japan and the Korean Peninsula also have a history spanning several thousand years. As early as the 3rd century BCE, inhabitants of the Korean Peninsula migrated to Japan’s Kyushu region, where they settled and prospered. Subsequently, Buddhism was continuously transmitted from China to Japan via Korea, initiating a long-standing civilizational exchange between the two regions. During the Ming Dynasty’s Wanli period (1592–1598), the Imjin War, or the Japanese invasions of Korea, occurred. Ultimately, with the support of the Ming Dynasty, Korea achieved victory. Following Japan’s Meiji Restoration, the domestic “Conquer Korea” (Seikanron) ideology gained prominence, advocating the use of military force to resolve issues on the Korean Peninsula. The subjugation of Korea became Japan’s second territorial objective after the annexation of the Ryukyu Islands. “Following France and the United States, Japan again implemented a 'gunboat diplomacy’ policy. In April 1875, three Japanese warships sailed up the Han River, approaching the Korean capital, Hanseong. In 1876, Japan forced Korea to sign the Treaty of Ganghwa.” [19] This was the first unequal treaty that modern Japan signed in its aggression toward Korea. “From the 1870s onward, Japan laid the foundation for expansion in Korea through the Treaty of Ganghwa, the Incheon Treaty, and the Hanseong Treaty.” [20] After the Russo-Japanese War, Korea became a Japanese protectorate. In 1910, Japan and Korea signed the Japan–Korea Annexation Treaty, through which Japan annexed the entire Korean Peninsula. Japan’s defeat and surrender in August 1945 ended seventy years of colonial rule over Korea that began with the Treaty of Ganghwa. In August 1948, the Republic of Korea was formally established in the southern part of the peninsula, originating from the Provisional Government of Korea founded during the March 1st Movement. From its inception, one of the key pillars of the South Korean government’s legitimacy was its anti-Japanese stance. Over more than seventy years since the founding of the Republic of Korea, Japan–South Korea relations have oscillated but never achieved genuine reconciliation. The outbreak of the Cold War prompted the United States to intensify its diplomatic engagement with Japan. In the 1951 Treaty of San Francisco with Japan, the US deliberately left the sovereignty of Dokdo (Takeshima) ambiguous, sowing latent conflict between Japan and South Korea. With sustained US efforts, and after nearly fourteen years of negotiations, the two countries signed the Treaty on Basic Relations between Japan and the Republic of Korea in June 1965, along with a series of related agreements, normalizing diplomatic relations. After normalization, bilateral relations experienced ups and downs but continued to make incremental progress. During the tenure of Nakasone Yasuhiro, relations began to warm, and from the early 1990s, the bilateral relationship entered a new stage. Although “the 1998 Joint Declaration on Japan–South Korea Relations set out a vision for bilateral relations in the new century, proposing development in political, security, economic, and cultural exchanges, current circumstances indicate that deterioration in Japan–South Korea relations has spread across multiple domains, and in the short term, improvement seems unlikely. Since 2000, frictions have persisted, with the greatest difficulties undoubtedly rooted in historical and territorial issues, yet overall, relations remain within a controllable range and the foundations of Japan–South Korea relations have not been undermined.” [21] Following the global financial crisis in 2008, economic conditions in Northeast Asia worsened. Japan and South Korea competed for industrial space and economic resources, while bilateral relations continued to decline. In 2012, as a South Korean presidential candidate, Lee Myung-bak visited Dokdo (Takeshima) for the first time in his capacity as President, bringing bilateral tensions into the open. During Moon Jae-in’s administration, the “dual policy” toward Japan led to a cooling of Japan–South Korea relations. After the 2018 G20 Summit in Argentina, bilateral relations hit a low point, with overlapping tensions across political, military, security, and economic domains, forming the current strained situation between Japan and South Korea, primarily reflected in the following areas:

Political Level: Currently, the unresolved issues primarily involve the labor case and the comfort women issue. The labor case refers to the historical event during Japan’s colonial rule over the Korean Peninsula, in which a large number of Korean laborers were conscripted to Japan to perform harsh labor. Although matters related to compensation, relief, and apologies were basically addressed under the pressure of the United States in the 1965 diplomatic communiqués and treaty annexes establishing diplomatic relations between Japan and South Korea, since 2018, the South Korean Supreme Court has re-examined the labor case and demanded that Japan continue to fulfill its compensation obligations. This demand was explicitly opposed by Japan, which maintains that the labor issue was properly resolved during the negotiations establishing diplomatic relations. The comfort women issue is another historical legacy of Japan’s aggression against Korea during World War II. The governments of Japan and South Korea held multiple rounds of negotiations, ultimately reaching the 2015 Agreement on the Comfort Women Issue. However, under Moon Jae-in’s administration, this agreement was annulled, and the “Comfort Women Foundation” established under the agreement was dissolved. The South Korean government subsequently demanded that Japan provide a new explanation and compensation for the issue, further escalating bilateral tensions. Although these historical legacy issues were explicitly addressed in the Treaty on Basic Relations between Japan and the Republic of Korea and its related annexes at the time of diplomatic normalization, many of them were only temporarily “shelved” due to Cold War imperatives and U.S. involvement rather than fundamentally resolved, leaving latent risks for future bilateral conflicts.

Military and Security Level: In December 2018, a South Korean destroyer, while on a mission, targeted a Japanese reconnaissance aircraft operating nearby with its fire-control radar, triggering the “fire-control radar illumination” incident and subsequent diplomatic negotiations between the two countries. In September 2019, Japan’s revised Defense White Paper downgraded South Korea’s position, and in November 2019, South Korea withdrew from the 2016 General Security of Military Information Agreement (GSOMIA) jointly signed with Japan, effectively suspending military intelligence sharing. The political significance of this withdrawal outweighed the operational impact, highlighting the lack of trust between the two countries [22]. The termination of GSOMIA signified a severe setback in security cooperation between Japan and South Korea, both members of the U.S.-led Northeast Asia alliance system. Looking ahead, as both countries remain under the U.S.-Japan-South Korea trilateral military framework and face U.S. pressure to improve bilateral relations, tensions may ease somewhat, but substantial improvement in the short term remains unlikely.

Economic Level: As early as 2004, South Korea was included in Japan’s trade “white list,” one of 27 countries recognized during a period of relatively friendly bilateral relations, reflecting Japan’s recognition of South Korea’s trade importance. However, under Moon Jae-in’s administration, worsening Japan–South Korea relations led to trade disputes. In July 2019, Japan imposed export controls on three semiconductor materials exported to South Korea, dealing a significant blow to South Korea’s advanced electronics industry. In August 2019, Japan announced its plan to remove South Korea from the trade “white list,” which was formally implemented in November. In response, South Korea took reciprocal measures and removed Japan from its own white list. As a result, bilateral economic relations cooled, prompting South Korea to pursue independent innovation in core components and seek alternative import sources, leading to a decline in bilateral economic interdependence. Japan and South Korea are respectively the world’s fourth and fifth largest exporters and are major participants in the global technology supply chain. Amid rising global trade protectionism—particularly the protracted trade war and increasing geopolitical risks between China and the United States—the trade conflict between Japan and South Korea poses a highly adverse impact on global economic development [23]. Since the 1990s, South Korea’s economic takeoff, along with its growing comprehensive national power and influence in international and regional affairs, has fostered rising national confidence. This provided the “hard power” foundation for the Moon Jae-in administration’s ability to respond strongly to Japan. Moreover, March 2019 marked the centenary of the March 1st Movement in Korea; any provocative actions by Japan toward South Korea during this period would not only inflame nationalist sentiment in Korea—difficult to quell in the short term—but also potentially undermine Japan’s long-term efforts to improve bilateral relations.

“The relationship between Japan and South Korea is complex, and some short-term solutions to address challenges may remain difficult to implement. However, the current situation also provides an opportunity for U.S. leadership to reverse the situation. Encouraging more active cooperation between Japan and South Korea is a strategic priority for the United States, which relies on this alliance network to maintain regional order.” [24] Superficially, the recent deterioration of Japan–South Korea relations manifests across political, military, and economic spheres. At a deeper level, however, both countries, as U.S. allies and key instruments for U.S. influence in Northeast Asia, constitute an essential pillar of the U.S. security framework in the region. Prolonged discord between Japan and South Korea could severely undermine the stability of the U.S.-Japan and U.S.-South Korea bilateral alliances, thereby impacting the broader Northeast Asian security framework as well as the security situation in the Western Pacific and South China Sea. The Trump administration, however, took limited measures to ease the divisions between Japan and South Korea, focusing more on domestic economic priorities and even selectively “ignoring” provocations from North Korea. Overall, the recent tensions in Japan–South Korea relations stem from historical grievances that have translated into comprehensive conflicts across multiple domains. Historical issues increasingly intertwine with contemporary disputes, and the intensifying trade conflicts between Japan and South Korea carry the potential to trigger political and security risks. “When the United States implements 'America First’ policies and trade barriers regardless of whether countries are allies or not, the common ground between Japan, South Korea, and the U.S. diminishes, even producing fissures in military cooperation. Meanwhile, China, Japan, and South Korea are promoting broad free-trade alliances in opposition to U.S. 'America First’ policies and trade barriers.” [25] For the United States, the shared ally of both Japan and South Korea, improvements in bilateral relations align with its own strategic interests. Under U.S. pressure and mediation, South Korea indicated it would differentiate between historical and contemporary issues and, at the last moment, delayed the termination of the General Security of Military Information Agreement (GSOMIA). Nevertheless, South Korea remains committed to its multilateralist national security approach. The U.S. role in facilitating a full restoration of Japan–South Korea relations has been very limited, achieving little in terms of easing recent disputes. In fact, Japan and South Korea need to find a pragmatic path for resolving their issues, exercise restraint, recognize the risks of worsening tensions, and avoid escalation or loss of control over the situation.

3. The new developments in China–Japan–Korea relations and their impact on the Northeast Asian order

3.1. The joint influence of China, Japan, and Korea on the future construction of the Northeast Asian order

The construction of a stable Northeast Asian order depends on close coordination among China, Japan, and South Korea. This requires not only robust bilateral and multilateral relations but also concerted trilateral efforts, ultimately forming a “synergistic force” capable of achieving optimal outcomes. Historically, three distinct orders have emerged in Northeast Asia. Chronologically, the first was the China-centered, hierarchical, and ethically infused East Asian tributary system; the second, established by Japan after the Meiji Restoration in the first half of the twentieth century, was the militarily and ideologically driven “Greater East Asia Co-Prosperity Sphere”; the third was the Cold War-era Northeast Asian order, dominated by the U.S.–Soviet rivalry, with the Korean Peninsula as its frontline [26]. The three countries share a unique and interconnected history. Chinese civilization, as the region’s ancient civilization, exerted profound and enduring influence on the development of Japanese and Korean civilizations. “China, leveraging its geographical advantages, comprehensive national power, and cultural influence, became the core state of East Asia and established a tributary system centered on itself.” [27] Unlike contemporary Western states or regional blocs, the ancient Chinese-led tributary system contained strong moral and Confucian “benevolence” elements. It formally recognized surrounding states such as Korea and Japan without interfering in their domestic affairs. Economic exchanges were more like gifts than market-based trade, reflecting a “give much, take little” approach that ended only with the decline of Chinese power. With Japan’s rise, Northeast Asia gradually came under a Japan-centered order. Even before the demise of the Chinese-led tributary system, Japan played a “dual role”: on one hand, it participated as a tributary to China; on the other, it used military force to subjugate weaker regional states, establishing a “mini-tributary system” under Japanese leadership. After the Meiji Restoration, Japan pursued a militaristic, expansionist path, occupying China, Korea, and other Asian countries, causing deep historical grievances. “Japanese diplomacy shifted from passive to proactive. Following pragmatism, Japan coordinated with major powers, aligning with Europe and the U.S., and pursued a 'secure the distant, attack the near’ strategy. Japan built a military state and aggressively expanded outward, becoming a source of wars in Asia and beyond. By its defeat in 1945, Japanese aggressions had reached East Asia, Southeast Asia, the Pacific, and the Indian Ocean, engaging nearly all major powers of the time.” [28] Following Japan’s defeat in World War II, Northeast Asia entered the third stage: a Cold War order shaped by U.S. and Soviet division of global spheres of influence, with the Korean Peninsula as the frontline of their confrontation. To this day, the peninsula remains a “living relic of the Cold War.” Among the three historical orders, the second and third have had the deepest influence on the contemporary trajectory of Northeast Asian order. Future development in the region will carry historical legacies, and interactions among China, Japan, and Korea will gradually form a new regional order.

Trilateral cooperation cannot bypass recognition and positioning on historical issues. Historical disputes between China and Japan, or between Japan and Korea, can be easily triggered by sudden events, escalating bilateral tensions and stirring nationalist sentiments. Only when Japan correctly addresses historical issues, or when all three countries face common challenges, can trilateral cooperation proceed smoothly. “In summary, China–Japan–Korea economic integration requires both solid technological cooperation and stable political-security relations.” [29] All three countries are advocates and beneficiaries of the multilateral trading system, committed to its maintenance. The evolution and reconstruction of Northeast Asian order will be a long and complex process. The principle of “peaceful coexistence” should serve as the highest guiding value, with pragmatic cooperation continuously expanded and deepened. Emerging disputes should be managed within a defined framework to prevent escalation. Despite structural contradictions, China, Japan, and Korea still possess broad areas for cooperation in trade, regional security, and other fields. Parties should approach potential frictions rationally and equitably, addressing each other’s concerns to achieve new breakthroughs. Looking ahead, the three nations should maintain strategic composure, seek common ground while respecting differences, pursue shared development, and adopt a long-term and forward-looking perspective to elevate the “new trilateral” relationship and foster a Northeast Asian order aligned with the common interests of the three countries and others in the region.

3.2. The U.S. factor in Northeast Asian order-building

After the end of the Cold War, the United States emerged as the world’s sole superpower, exerting influence across multiple domains. On one hand, it sought to consolidate its “unipolar moment” in ways favorable to its national interests; on the other, it actively sought to prevent any region from developing forces capable of challenging its global primacy. Consequently, Washington has consistently maintained a cautious, often obstructive stance toward deep trilateral cooperation among China, Japan, and South Korea. U.S. political intervention remains the largest external obstacle to the three countries’ concerted efforts. Because of the U.S. factor, the Northeast Asian order that China, Japan, and South Korea could jointly construct cannot resemble the integrated, European Union–style cooperation the three nations might envision. Nor has it achieved the full realization of a China–Japan–Korea community of shared destiny. Among the three bilateral relationships: China–Japan continues to face unresolved historical disputes and the territorial conflict over the Diaoyu/Senkaku Islands; China–Korea has temporarily eased the THAAD issue, but the North Korean nuclear problem remains unpredictable, affecting bilateral stability; Japan–Korea still contends with historical grievances and the Dokdo/Takeshima territorial dispute. These disputes involve national sovereignty and core interests, making immediate compromise highly unlikely. They are also prone to escalation due to various triggers. By “intervening” in Northeast Asian affairs, the U.S. maintains a “conflict without rupture” state among China, Japan, and Korea, which best serves its strategic interests: preventing the three countries from forming a synergistic bloc protects the U.S.-led “Kissingerian order” in Northeast Asia from being challenged.

Most countries in the Asia-Pacific and West Asian regions are either U.S. allies or maintain quasi-alliance-level ties with Washington. Compared to Middle Eastern oil exporters, non-aligned South Asian countries like India, and smaller Southeast Asian states, Japan and South Korea are far more tightly linked to the U.S. Strategically: For Japan, centuries of colonial legacy and historical invasions create both strategic and psychological burdens. As a four-island nation with limited natural resources, Japan relies on an advanced maritime transport system to import resources. Securing sea lines of communication is vital for its survival and development. Its alliance with the U.S. both protects these sea lanes and mitigates strategic pressure from China’s rise. For South Korea, since its founding, the North Korean threat has been persistent. The U.S.–ROK alliance provides an external security buffer, allowing Seoul to respond effectively to potential threats from Pyongyang. Thus, Japan and Korea objectively depend on U.S. support and coordination, creating opportunities and conditions for U.S. involvement in Northeast Asian affairs. Given the current limitations on the capabilities and regional influence of China, Japan, and Korea, a fully autonomous Northeast Asian cooperative framework has yet to emerge. Trilateral interactions largely operate within a U.S.-led rules system. Despite geographical proximity, historical grievances and present-day conflicts prevent the formation of a tightly knit community among the three nations. Intensifying U.S.–China strategic competition and the long-standing influence of U.S. policy on Japanese and Korean foreign policy further complicate trilateral relations. Moreover, U.S. military presence in Japan and South Korea directly threatens China’s security. The Trump administration’s “Indo-Pacific Strategy,” an upgrade of the “Asia-Pacific Rebalance,” demonstrates that Washington is unlikely to relinquish the half-century-old Northeast Asian order it has carefully built, further constraining the trilateral potential for a closely coordinated framework.

Currently, warming China–Japan and China–Korea relations are partly attributable to U.S. policies toward Japan and Korea during the Trump administration. With relative U.S. decline and greater diplomatic autonomy for Japan and Korea, both countries have consistently sought to expand economic cooperation with China. The December 2019 summit of China–Japan–Korea leaders in Chengdu marked an important milestone in this process. Drawing inspiration from the tripartite division of Wei, Shu, and Wu at the end of the Eastern Han dynasty, Abe Shinzo first articulated the concept of a “New Trilateral” among China, Japan, and Korea. Unlike the historical “Old Three Kingdoms,” this new framework emphasizes cooperation and win-win outcomes rather than internal rivalry. The emergence of the new trilateral structure reflects profound shifts in the international order and the interplay of U.S.–China, U.S.–Japan, and U.S.–Korea frictions. Efforts by China, Japan, and Korea to resolve differences and expand cooperation represent rational choices consistent with their core national interests. “Looking back over 20 years of cooperation, the path has not always been smooth, but the three nations have persevered and now stand at a new historical starting point. First, there is broad consensus on defending multilateralism and the free trade system. Second, there is ample space for pragmatic cooperation. Third, the three countries play an important coordinating role in promoting regional and global stability and prosperity. In the next decade, China–Japan–Korea cooperation will continue to be a driver of Asian and even global development.” [30] These trends in Northeast Asian order offer the potential to inject fresh momentum into both regional and global economic development.

3.3. China–Japan–Korea economic cooperation: a prelude to Northeast Asian order-building

During the 8th China–Japan–Korea (CJK) Summit in December 2019, the three countries “issued the Outlook on CJK Cooperation for the Next Decade and approved early harvest project lists under the 'CJK+X’ framework.” They agreed to “commit to promoting regional economic integration, expedite the signing of the Regional Comprehensive Economic Partnership (RCEP), and accelerate negotiations on a China–Japan–Korea free trade area (FTA).” [31] In practice, trilateral cooperation has actively promoted the construction of a Northeast Asian integration framework and the development of a Northeast Asian community. The three economies exhibit strong industrial complementarity: China’s vast service market and trade potential are highly attractive to Japan and Korea. Expanding openness and attracting Japanese and Korean investment also align with China’s “bringing in and going out” strategy. To maximize the effectiveness of CJK cooperation, it is necessary to enhance mutual strategic trust. Given China’s economic scale advantage and the still-limited political trust between Japan and Korea, China should play a leading role in trilateral cooperation, acting as a bridge and mediator when tensions arise between Japan and Korea, helping to reconcile differences and consolidate bilateral consensus. From a global perspective, the current international environment is favorable for CJK cooperation in promoting a new Northeast Asian order. The Trump administration’s conservative turn shifted U.S. focus from international affairs to domestic agendas, withdrawing from multilateral trade frameworks such as the Trans-Pacific Partnership (TPP). In remaining trade mechanisms, the U.S. often adopted a passive stance, becoming, in economic matters, a “silent partner.” Its inward-looking policies were particularly pronounced and, given America’s relative decline, unlikely to reverse in the short term. As the U.S. reduced its role in multilateral trade frameworks, gaps emerged in maintaining effective regional and global trade operations. Following the U.S. withdrawal from TPP, Japan led the establishment of the Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP), comprising the remaining 11 countries, and actively promoted the Regional Comprehensive Economic Partnership (RCEP), which includes China. Japan thus sought to replace the U.S. as the leader of multilateral trade in the Pacific region. “Unlike previous '10+1’ FTA frameworks, RCEP integrates ASEAN and six other countries under a single FTA framework, linking the ASEAN Economic Community with the economies of other member states and laying the foundation for a broader regional economic community.” [32] “Under Trump’s protectionist policies, including trade wars with China and the EU, RCEP serves as a bulwark defending the free trade system.” [33] During the Trump era, divergences in interests between the U.S. and South Korea led to some distancing in the U.S.–ROK alliance. Compared with China and Japan, South Korea’s external trade dependence is higher. Therefore, expanding multilateral trade and constructing a Northeast Asian economic community through RCEP aligns with South Korea’s economic development interests. The signing of the China–Korea FTA in June 2015 marked the formal establishment of the bilateral free trade area and represented a key step toward a trilateral FTA. The warming of China–Japan relations provides a solid foundation and rare opportunity for CJK FTA negotiations. Once concluded, the trilateral FTA would not only deepen internal economic and trade cooperation but also enable the three countries to participate in international competition as a unified bloc. “Negotiations on the remaining RCEP provisions are being expedited, with bilateral market access talks underway, legal reviews expected to be completed by June 2020, and the formal signing anticipated in November 2020.” [34]

“China, Japan, and Korea have all benefited from free trade and support it. Under current circumstances, the three countries should stand firmly together to safeguard a rules-based multilateral free trade system, clearly oppose protectionism and unilateralism, and take the lead in formulating a blueprint for an East Asian economic community.” [35] The CJK trio “will continue to strengthen economic and trade cooperation under frameworks such as APEC and the G20, jointly defend the WTO-centered multilateral trade system, promote globalization toward a more open, inclusive, balanced, and mutually beneficial direction, and advance the construction of an open global economy.” [36]

4. Conclusion

“Northeast Asia stands at a crossroads. One path leads to sustained economic growth, regional integration, and globalization, while the other leads to trade wars, territorial disputes, and an arms race fueled by resurgent nationalism.” [37] From both historical and contemporary perspectives, “only when regional security issues are no longer sensitive and prominent can the weight of traditional military-based power in East Asia’s power structure decline, allowing structural power grounded in economic interdependence to translate more fully into regional influence. This would shift the primary source of East Asian leadership from the former to the latter.” [38] Historically, the trajectory of Northeast Asian order has often displayed a separation between politics and economics. “Throughout Northeast Asian history, regional cooperation frequently reverses just when progress seems imminent. For Northeast Asian regional cooperation to break out of this historical cycle, it is essential to overcome adverse factors and prevent major setbacks.” [39] Minimizing the negative influence of the United States, the North Korean nuclear issue, territorial disputes, and historical legacies is fundamental to achieving peace in Northeast Asia. “Therefore, the primary challenge facing Northeast Asia is how to integrate nationalist forces while leveraging global thinking and regional cooperation to foster a vibrant civil society.” [40] Differences in institutional development and domestic governance among Northeast Asian countries have led to uneven political progress, underscoring the need for China, Japan, and Korea to leverage their respective comparative advantages, optimize resource allocation, and strengthen cooperation in emerging industries. Looking ahead, the construction of a stable Northeast Asian order requires China, Japan, and Korea to make measured concessions, deepen regional identity, and reinforce cooperative consensus. By minimizing negative spillover effects and enhancing the autonomy of each actor, the three countries can jointly guide the evolution of Northeast Asian order toward a more stable, integrated, and prosperous future.