Improving the US–ROK–Japan Defense Posture in the Indo-Pacific

Trade and Investments in Dual-Use Commodities amid the Race for Technological Supremacy

The second Trump Administration marked a return to bilateralism, as part of its transactional policy, with little trilateral cooperation, except for a foreign ministers meeting. On the contrary, significant concerns about economic insecurity arose as Washington imposed tariffs on rivals and allies alike, in the vein of its first administration, driven by protectionist and economic nationalist logic beyond the US-China trade war. For both the US’s crucial foreign investors, the threat culminated at 25% on exported goods. If these tariffs were later revised to 15%, the resulting uncertainties prompted the two neighbors to consider hedging, including a PRC-ROK-Japan top-level summit, or with the possibility of reestablishing economic and diplomatic engagement between Seoul and Beijing (Niquet, 2025). Yet, while these dynamics do not contribute to the consolidation of the triangle, their trade policies toward products at the economy-security nexus highlight an alignment in maintaining strategic competition in the technology race against China.

The trade agreements concluded by Japan and South Korea with the United States include several provisions on dual-use items, that is goods with both civilian and military uses, such as critical minerals and emerging technologies. These deals reflect core industrial priorities of the three partners and mirror China’s objective to enhance its leadership in such sectors through its military-civil fusion policy, which seeks to improve its military posture. Trilateral efforts aspire to secure supply chain resilience, particularly regarding critical minerals, an industry considerably dominated and weaponized by Beijing as part of its strategy to manage dependencies and control technologies (Yu, 2025). Before 2025, the three partners each developed national legislations to reinforce their respective financial and governance instruments to support domestic industries and secure critical minerals supply chain: South Korea enforced four laws to minimize risk, maximize fast recovery, and prepare for resources’ weaponization; Japan formalized the stabilization of significant materials supply in its 2022 Economic Security Law; and the United States registered the protection of provisions with two significant laws, as well as with annual National Defense Authorization Acts (Villalobos et al., 2025). Although trade and investment agreements are insufficient in bolstering the triangle’s posture, recent bilateral initiatives illustrate efforts for coordination and diversification, including within the Mineral Security Partnership. Moreover, Seoul and Tokyo reinforced their collaboration within the scope of two ROK-Japan Mineral Resources Cooperation Dialogue meetings, inaugurated in February 2025, to promote stable supply chains and producer-consumer relations amid growing instability (Ministry of Trade, Industry and Resources, 2025). On the other end of the triangle, the Trump Administration has endeavored to acquire mining and processing assets and sought to accelerate the development of the US critical mineral sector through massive investments (Bentley, A. & Goldman, J., 2025). It also involved reinforcing ties with allies, notably through a US-Japan agreement, which opens up new opportunities for cooperation—including with third parties—to coordinate economic policy instruments within investment and financing frameworks (White House, 2025b). The US-ROK-Japan alignment seeks to diversify trade and investments targeting critical minerals. In doing so, the triangle aims to reduce the potential for its industries to be weakened by the weaponization of dependence on crucial products.

Critical minerals are top priorities of the partnership because they are fundamental to the production of semiconductors. These chips are strategically vital for collective defense, since they are used in smart systems like drones, satellites, and cruise missiles. Washington and Beijing are leaders in this sector, but South Korea and Japan have emerged as crucial actors with the potential of balancing the US-China rivalry while reinforcing the triangle’s technological edge. On the one hand, Tokyo strives to rebuild its national industry by implementing strategic autonomy, to reduce its dependence on other states, and strategic indispensability, to ensure its presence in relevant sectors (Institut Montaigne, 2025). Its increasing investments in microelectronics are driven by economic security objectives to reinforce the supply chain resilience of components necessary for the production of these chips. In contrast, South Korea produces a substantial share of advanced chips, while still heavily dependent on China’s raw materials. Samsung Electronics and SK Hynix are dominant companies in this field and shaped Seoul as an indispensable partner. As semiconductors became South Korea’s top source of exports, its cooperation with the United States provides strong connections to major US technology companies, like Nvidia, Tesla, and Microsoft (Lee, 2025). Yet, this primacy creates potential vulnerabilities regarding interdependence with national and international ramifications. The Chip 4 alliance, launched under the Biden Administration, sought to palliate these weaknesses while enhancing the US posture by fostering strategic coordination between the members of the triangle and Taiwan to contain China’s industrial leadership (Pendharkar, 2025). The Trump Administration, however, weakened the US posture in the semiconductor industry with imports falling by 11% between 2024 and 2025 (US Census Bureau, 2025), while South Korea recorded a 3.8% increase in total exports, totalling to $700 billion (France 24, 2026). It is the result of the implementation of tariffs as well as reshoring and decoupling practices at the expense of friendshoring policies to favor domestic production, which equally fostered fewer opportunities for trilateral collaboration. Despite such hindrances, their policies remain aligned in strengthening their positions as opposed to China, which is fundamental amid the ongoing technology race and the broader trade-security landscape.

The production of chips is essential for asserting leadership in the context of the technology war, notably regarding emerging technologies that are equally at the crossroads of civil and military use. These technologies—and especially artificial intelligence—optimize threat detection and its response, airborne and domestic surveillance, as well as the autonomy of combat systems. They are increasingly at the center of national defense policies, with investments aimed at either enhancing or maintaining defense superiority to compete with China, which intensified the modernization of its military programs, driven by its intelligentized warfare strategy (Bhatia & Pallvi, 2026). Although the United States is the primary actor, seconded by its main rival, Japan and South Korea have become significant leaders, respectively in fourth and fifth place in 2025. This growth will expand as they have announced massive private and government investments to support the AI, quantum, and biotechnology sectors, as well as reinforce bilateral cooperation with the United States (Rosenbach et al., 2025). Such initiatives include significant agreements to bolster the coordination of US-ROK and US-Japan AI exports, driven by improved collective development and security efforts (White House, 2025d). Simultaneously, Washington introduced a series of measures to keep pace with the evolving strategic landscape and rapidly intensifying technology race, which includes a tightened collaboration with allied leaders. The AI Action Plan, launched in July, intends to create a US-led alliance with essential partners through investments, coordination, and alignment. Its objective is to compete with and reduce reliance on China by favoring and building upon Washington’s technology (White House, 2025a). The most significant measure undertaken is the Pax Silica framework. Launched in December, the US-led initiative frames a partnership with crucial leaders and allies in the emerging technology sector, notably Indo-Pacific powers like South Korea and Japan, which featured among the inaugural members. The purpose is to innovate through partnerships with technology companies, while reducing dependencies through supply chains securitization and establishing a prosperous economic security with resilient infrastructures (Coyne, 2025b). The control of emerging technologies has thus materialized as a decisive pillar in the US-ROK-Japan technological and strategic cooperation, shaping a reinforced investment collaboration towards goods with defense potential and fashioning a sharper competitive alignment in the technology race.

If the partnership principally resorted to bilateral efforts and unilateral coercive policies, in the vein of Donald Trump’s transactional policy, these initiatives reveal a strong US-ROK-Japan alignment as well as opportunities for enhanced cooperation. Their respective yet cohesive posture emphasizes the significance of supply-chain resilience, from critical minerals to emerging technology, to maintain strategic primacy. In seeking to minimize reliance, the three partners have engaged in de-risking strategies and accelerated the development of their industrial technology base to rebalance China’s leadership and reduce the weaponization of interdependence. These policies underscore a trilateral consensus toward the production of dual-use commodities, aligned with the strategic environment’s evolution.

From Responsibility-Sharing to Burden-Sharing: The Consequences of the US Transactional Policy on the Triangle’s Strategic Alignment

Since Trump’s first year back in office, the minilateral institutional cooperation considerably reduced, despite a momentum set forth in 2024. Several instances of joint exercises meant to strengthen interoperability, such as Freedom Edge 25—the first trilateral multi-domain exercise combining air, maritime, and cyber forces—reveal practical-oriented coordination across lower- and working-level mechanisms. Yet, the lack of top-level meetings, apart from trilateral defense talks, did not advance a transformative consolidation of their collaboration regardless of the strategic environment. On the contrary, the head-of-state synergy illustrates the revival of bilateralism, aligned with the US bargaining policy, which could disrupt the onset of the triangle, already frayed by ROK-Japan frictions and Washington’s political instability from one administration to another.

Beyond trade matters, the transactional policy enforced by the United States also reflects strategic issues within the trilateral partnership itself. Like during his first term, Trump threatened to reduce or relocate troops stationed in South Korea even though the Special Measures Agreement was signed in 2024. This prompted Congress to legally prevent such an action without certification from the legislative branch. Characterized by a hard-line stance, the US policy implemented indicates a shift from responsibility-sharing to burden-sharing, whereby bilateral arrangements meant to offset the asymmetric costs shouldered by the United States as primary security guarantor overshadow the minilateral collaboration intended to reinforce deterrence and the liberal order’s posture in the region. Reaching up to 5% of their GDP, the excessive demands for increased defense spending, supported by the leverage of foreign aid (Tursun & De Kruijf, 2025), exemplify this shift. As stated in the 2025 National Security Strategy, both allies are urged to reinforce their own defense and assume a greater share of the burden to reinforce their regional posture while reducing the US share. If South Korea has not commented on this document, in contrast, the Japanese government has criticized its content, stating that bolstered capabilities and defense costs were already part of Tokyo’s strategic objectives, a policy implemented on its own accord and ready to reach 2% of its gross domestic product by the end of 2026 (Pollman, 2025). This declaration aligns with the draft of a record-high defense budget. More recently, during the Reagan National Defense Forum, the US Secretary of Defense Hegseth praised Seoul’s commitment to enhancing its conventional defense spending to 3.5% of its GDP (US Department of War, 2025). If frictions arose, the two Asian partners have maintained aligned policies to meet the demands for increased burden-sharing. Such an engagement and accelerated efforts, despite coercion, offer opportunities to assume a greater role in the Indo-Pacific while developing their own military industry amid rising tensions.

The region is gradually becoming more militarized, and the US-China rivalry is confronted by a significant asymmetry in their approach to developing their defense industry. Although Washington remains the primary military actor on the international stage, Beijing has actively endeavored for years to modernize and shape a world-class military by the middle of the century through investments in and acquisitions of capacities on a wartime footing. However, multiple reports, such as the last annual report to Congress discussing China’s military and security development, state that these increasing efforts to expand its defense industrial base, both in terms of investment and rapidity, expose the US territory to significant vulnerabilities (US Department of Defense, 2025). In the long run, China could outpace the United States and counterbalance the liberal order. Such a scenario could have severe repercussions for the Indo-Pacific and the US-ROK-Japan partnership, especially in the event of a conflict with Taiwan. As a result, the Pentagon is outlining a policy through several strategic documents to modernize the US defense industrial base from defense procurement to capacity building, as well as tackling arms sales to reinforce allies’ capacity to engage in collective defense. This policy is coherent with the transition toward burden-sharing, particularly for powers located near the First Island Chain, as mentioned in the National Security Strategy, and following from the Acheson Line and the Nixon Doctrine. Yet, the Trump Administration does not seek to reduce US regional engagement, despite Washington using the US security umbrella as a bargaining chip and its failure to clearly identify security threats, like North Korea, which is not mentioned once in strategic documents. Rather, the White House frames its access to the Indo-Pacific around expectations that regional allies, including South Korea and Japan, will contribute their own developed capabilities in collective defense. Such a strategy thus requires enhanced military buildup and cooperation, even though the Republic of Korea and Japan only concluded two arms deals each, respectively reaching $145.8 million and $1 billion (Defense Security Cooperation Agency, 2025), to acquire defense material from the United States. The burden-sharing policy provides grounds for South Korea and Japan to improve their military capabilities and assume a greater responsibility in the region's security. Yet, the lack of trilateral efforts in the defense procurement sector, if not for South Korea’s promise to purchase up to $25 billion in US military equipment by 2030 (White House, 2025e), whereas Seoul and Tokyo rely on the United States as a security guarantor, creates a gap between Washington’s excessive demands and its two partners’ industrial buildup.

The US shipbuilding is particularly vulnerable, as it weakens the Navy’s modernization, especially since the industry is largely dominated by China. The following leaders in that sector, far ahead of the United States, are South Korea and Japan (Funaiole et al., 2025). As such, the gap faced by Washington creates opportunities for defense cooperation on a trilateral basis. Beyond the 2026 National Defense Authorization Act, which favors these two allies in trade regarding this strategic sector, the bilateral trade agreements concluded during the summer of 2025 include several provisions in this regard. As part of the $550 billion promised, Tokyo will invest to “revitalize the US industrial strength and economic security” (Chou, 2025). These measures were completed with a memorandum of cooperation to increase shipbuilding capacity in both states as well as alignment in terms of procurement, investments, and technology initiatives (White House, 2025c). South Korea, however, plans to invest $150 billion in shipbuilding, which will allow Seoul to reinforce its presence in the US industries. As part of a partnership labeled as “Make American Shipbuilding Great Again,” its commitment lies in its investment in commercial and military ships, as well as training and supply of a workforce. Three of the top South Korean defense companies are expected to expand their cooperation with the partner: Hanwha Group, located in Philadelphia, will become the first builder of LNG carriers and increase tenfold the number of vessels; Samsung Heavy Industries will focus on the construction, modernization, and maintenance of ships; and HD Hyundai will develop advanced technological equipment and marine logistics infrastructures (Toso, 2025). Moreover, recent debates around the topic of nuclear-powered submarines have led to converging policies. In October 2025, South Korea and the United States concluded an agreement to jointly develop Seoul’s first nuclear-powered submarine (Howell, 2025). As part of the shift toward burden-sharing, the purpose is to transfer a share of the regional deterrence to its ally, especially as US capabilities in the Indo-Pacific waters are outnumbered by those of China. This acquisition would thus enhance South Korea’s defense posture on regional and global scales, as well as escalate the militarization of the Indo-Pacific. In response, the government mentioned the possibility of Tokyo acquiring such capabilities to face the evolving regional landscape, departing from its traditional postwar posture (Indo-Pacific Defense Forum, 2025). The triangle’s interoperability regarding the shipbuilding sector reveals crucial opportunities to mutually strengthen their defense industrial base, not only to boost alignment but also to provide significant occasions for US allies to bolster their role in the Indo-Pacific region and among the most prominent powers globally.

If the Trump Administration’s transactional policy hinders the US-ROK-Japan partnership on an institutional level, the US-ROK and US-Japan relations indicate a trilateral, sector-specific alignment despite coercion and tensions. These opportunities for burden-sharing, whether through investments or partnerships that merge with long-term domestic strategic priorities, create a mutually beneficial dynamic for the three partners, while enforced on a bilateral basis. First, it reinforces the US defense industrial base, allowing the superpower to modernize its military and remain competitive. Second, it prompts a strong minilateral alignment with an interdependence that will prevent hedging policies while fostering opportunities to reinforce cooperation within the trilateral partnership. Third, it will reduce the potential for Beijing to weaponize interdependence in the shipbuilding sector and paralyze the triangle in the region, in particular in the event of a conflict.

Strategic Entanglement and Leadership in the Multipolar Environment of the Indo-Pacific

The Republic of Korea and Japan have been longstanding regional agents of the liberal order, even though they are entangled in a web of economic dependence with China, like most powers in the Indo-Pacific. Yet, the recent evolution of alliance configuration tied to the United States illustrates a structural shift from the traditional hub-and-spoke model, a system favoring bilateral forms of ties, to an intricacy of partnerships representing the latticework similar to NATO that the Biden Administration sought to develop. Apart from the US-ROK-Japan partnership, several mechanisms like the Quadrilateral Security Dialogue and the US-Japan-Philippines cooperation have emerged as crucial balancing frameworks in the region to collectively tackle the economic and military security threats posed by China. This entanglement is the combination of what De Castro frames as system-level and unit-level forces, referring to the US-led multilateral vision and efforts seconded and strengthened by unilateral strategies of partners (De Castro, 2025).

In line with its impact on the US-ROK-Japan partnership, the Trump administration has disrupted the formation of a broad network of alliances and hindered collective action aimed at improving the rules-based order in the Indo-Pacific. The QSD is one of the most significant initiatives reflecting this change. In early 2025, Washington had signaled its willingness to pursue cooperation with its three partners within this framework, similar to the stance adopted eight years ago. As such, the four partners joined twice, yet their cooperation has significantly decreased since the trade war, and cohesion and alignment are tested by the US-India dispute in trade and energy matters. New Delhi’s continued energy trade and military cooperation with Russia, as part of its multi-alignment and strategic autonomy policy, has led to the escalation of frictions, from raised tariffs peaking as the highest imposed on a partner to a rapprochement with authoritarian rivals amid the Shanghai Cooperation Organization summit (Pande, 2025). Moreover, India’s marginalization despite its predominance in the technology sector during the inauguration of the Pax Silica initiative sheds light on a misalignment that limits the partnership’s coordination, in particular as the United States bolstered its technology policies in the region with strengthened ties with Australia in the defense and critical minerals sectors (Coyne, 2025b). In contrast, Seoul and Tokyo have increasingly enforced policies meant to improve ties with Indo-Pacific powers while remaining strongly aligned with their main partner, symbolizing a gradual shift from the dichotomy of one order versus the other, as well as a diversification of partnerships to assess both strategic and economic security imperatives. Both states are massively trading and investing in the critical minerals and emerging technologies sectors with partners like India and Australia, and more broadly with Central and Southeast Asian states (Lam, 2025). The regional cooperation of these powers aims to decrease critical dependence on China by creating resilient supply chains, while also reducing the potential of economic coercion and disruptions, whether from one superpower or the other, as well as military confrontation. Such individual yet pluralist policies are adopted by most middle powers, including the two QSD powers, to reinforce regional stability, balance economic and strategic security, and avoid binary restraints of the US-China competition.

The US-ROK-Japan partnership has maintained a coordinated stance on China’s maritime expansion, which jeopardizes the stability of the Indo-Pacific, notably with a trilateral maritime collaboration framework that includes joint exercises and capacity-building assistance for Southeast Asian partners (Roy, 2025). Yet, their posture toward Taiwan, a territory impacted by such issues, underscores differing stances, despite their official stance on the one-China policy and entanglement with Taipei in the technology sector. Ranging from presidential to ministerial declarations, the Lee Administration has reinforced strategic ambiguity about South Korea's policy in the event of an invasion of Taiwan, either dismissing this scenario or denying the relevance of the matter in its relations with both China and the United States (Cho, 2025). Such a hedging strategy illustrates its strategic neutrality to avoid antagonizing its neighbor, for its trade critically depends on it. Indeed, China instrumentalized such reliance, and Japan is the latest to experience it. A diplomatic crisis surged following Sanae Takaichi’s statement about the protection of US forces, according to which a military escalation over Taiwan prompting Washington’s intervention could represent an “existential threat” to the security of Japan, and consequently lead to the enforcement of collective self-defense as stated in its existing security legislation of 2015 (Fakuta & Sakaki, 2025). Although this declaration did not refer to the protection of Taipei, Beijing has retaliated with confrontational discourse and economic coercion, like boycotts, bans, export curbs of dual-use goods, and territorial adventurism in Okinawa’s vicinity. The lack of reaction regarding the escalation of tensions has increased concerns about the US posture toward Taiwan. The delayed publication of strategic documents, combined with the stabilizing US–China tensions, occurred as Taipei was expected to bolstered investments in the US semiconductor industry to strengthen the Trump Administration’s reshoring policy, although the United States heavily relies on Taiwan’s industrial production. The National Security Strategy, while not clearly defining threats, emphasized the security of the First Island Chain and prompted regional allies to balance China’s maritime expansionism. The Trump Administration also pacified such uncertainties with its second arms transfer, the largest-ever US-Taiwan arms sale deal, which reached $11.1 billion, surpassing those concluded during the Biden Administration (Sharp, 2025). The US policy enforced with allies seeks to maintain a capacity balance to confront China’s defense modernization, with consequences for the Indo-Pacific, as it fosters and reinforces the escalation of militarization in the region.

The United States has established close defense relations with Indo-Pacific powers, notably with the Philippines, Vietnam, Indonesia, and Thailand, through the National Guard’s State Partnership Program. Defense export cooperation is a crucial indicator to assess the US role in the region, as a primary arms seller. Apart from Taiwan, the sale of high-demand military kits has decreased over the first year since Trump’s return compared to previous years. Washington called for allies and partners to acquire such assistance, but the lack of affordability and adequacy, coupled with US industrial vulnerabilities, increased concerns over the United States defense commitments (Winger et al. 2025). However, South Korea and Japan, which became major defense powers on the international stage, represent crucial balancing powers capable of palliating such weaknesses while reinforcing their own leadership in the Indo-Pacific. Tokyo seeks to further alleviate the restrictions on arms exports despite foreign sales being authorized under specific conditions. The rationale is to provide a broader range of equipment to allies and partners amid rising tensions and meet demands at a quicker pace if a conflict were to break out (Dominguez, 2025). The departure from its traditional stance would enhance the competitive dimension of its defense industrial base, with additional technology-oriented corporations, along with the improvement of its military aid program for like-minded partners in Southeast Asia. Besides arms transfers to India and Indonesia, Japan has reinforced its cooperation with the Philippines amid the modernization of its military base, as well as with Australia, with whom Mitsubishi Heavy Industries concluded the state’s largest defense contract (International Crisis Group, 2025). In comparison, South Korea has become a credible arms export partner and is expected to intensify its strategic posture through defense and technology research. As an export-driven economy, Seoul has built its defense industry on trade with regional powers like India, Indonesia, Malaysia, the Philippines, and Thailand, and ascended as one of the fastest-growing arms producers on the international stage, with an industry focused on cheaper and more reliable capacities. Yet, apart from Australia, South Korea recently shifted its exports from the Indo-Pacific toward the Middle East, one of China’s main playgrounds, and especially Europe, to which half of its exports were intended, becoming a significant alternative to the United States (Kim & Liang, 2025). As significant powers, the modernization, reconfiguration, and reinforcement of their posture as arms exporters highlights a trilateral alignment in tune with the increasing militarization and the rising tensions in the region. If its aim is to consolidate relations with nearby middle powers, South Korea and Japan could emerge as credible alternatives to the United States.

The resumed bilateral focus and trade tensions under the Trump Administration have severely impacted the resilience of the system-level forces, including the reconfiguration of regional alliances with essential powers previously sought. Yet, the unit-level forces embodied by South Korea and Japan, although not always aligned, have evolved to provide more stability while confronting China, creating an even more complex regional environment. By actively engaging in defense reconfiguration, both states have emerged as crucial alternatives for other powers and reinforced their defense posture through strengthened regional alliances and industrial bases.

Conclusion

Political changes have impacted the three states that constitute the US-ROK-Japan partnership, yet 2025 has not symbolized a reset of the triangle’s relations, nor a heightened cooperation. On the contrary, less institutional coordination was fostered by the revival of bilateralism and transactional policies, as well as by the Trump Administration’s elevated demands for increased burden-sharing and military expenditures regardless of the long-term, but slower-paced domestic and converging policies enforced by Japan and South Korea. However, the three partners are closely aligned in the defense sector and the trade of dual-use commodities amid rising regional militarization, the evolution of the strategic environment, and the race for technology leadership. From raw materials to finished products, mutually beneficial opportunities have emerged to reinforce their defense industrial base, accelerate innovations to remain competitive, and contain China’s growing primacy while minimizing dependence, the prospect of its weaponization, and hedging approaches.

Although several internal and external factors test the actors’ engagement and the partnership’s resilience, their defense posture in the Indo-Pacific indicates a continued momentum despite tensions for Washington and opportunities for both Tokyo and Seoul to play a more active role. If the Trump Administration has not strictly disrupted the reconfiguration of alliances, its rejection of multilateralism and bargaining policy jeopardizes the collective action of some partnerships. On the other hand, the diversified defense partnerships, coupled with bolstered strategic autonomy, have enabled South Korea and Japan to reduce their reliance on both China and the United States while materializing as significant alternatives for other regional powers. Not only does this restructuring balance economic and strategic security dynamics while reinforcing their deterrence authority, but it departs from the binary polarization resulting from the great power rivalry to shape a regional environment aligned with the multipolar order and contribute to the accelerating militarization of the region.