Analysis of U.S. Security Policy Toward Japan Under Trump's Second Term‌

Abstract‌: Since Trump's second term, U.S. alliance policy has exhibited a selective strategic retrenchment. Although the overall emphasis on "America First" has intensified, the U.S. has demonstrated a strong willingness to cooperate with Japan on security matters, resulting from the joint implementation of the "Trump approach" and the "Trump team approach." The U.S. policy demands primarily manifest in two aspects: on one hand, questioning the fairness of the U.S.-Japan alliance, requiring Japan to increase its defense spending, raise its contribution ratio to the costs of U.S. forces stationed in Japan, and assume greater responsibilities within the alliance; on the other hand, within the framework of Indo-Pacific minilateral security cooperation, strengthening U.S.-Japan joint deterrence through an alliance management approach that leverages Japan's security role, deepening economic security and defense industry cooperation, but without emphasizing the shared values of the alliance. The primary objective of U.S. security policy toward Japan is to maximize U.S. security interests at the minimum cost, ensuring "America First," serving its "Indo-Pacific Strategy," and pushing Japan to the forefront of regional security to fully leverage Japan's unique role in containing China. This has led to Japan's elevated status in the U.S.-Japan alliance, increased Japanese distrust toward the U.S. on security matters, accelerated the transformation of the U.S.-Japan alliance, heightened the risk of regional conflicts, and further complicated Sino-Japanese security relations.

Trump's second term has further emphasized "America First," reducing the U.S.'s willingness to contribute to alliances. The protectionist and transactional characteristics of its alliance strategy are evident, resulting in complex changes in U.S. security policy toward Japan. Unlike the contradictions and turbulence in the economic field, U.S.-Japan cooperation in the security domain has continued to strengthen, demonstrating a degree of policy continuity, with the strategic consensus on security in the U.S.-Japan alliance being further deepened. However, unlike the traditional model of strengthening the U.S.-Japan alliance, the Trump administration no longer adopts the non-coercive alliance management approach seen during the Biden administration but instead exhibits a distinct feature of strong pressure, avoiding greater costs and losses for itself in the alliance relationship, bearing the distinct imprint of the "Trump style." Overall, the Trump administration has promoted the transformation of U.S.-Japan alliance management. While not abandoning its goals of strategic expansion and military deterrence in the Indo-Pacific region, it has made the intention to view the U.S.-Japan alliance as a "tool" more apparent. U.S. security policy toward Japan is more based on U.S. interests rather than the security and interests of the alliance, requiring Japan to assume greater security responsibilities and play a more active security role, pushing Japan to the forefront of regional confrontation, and selectively conducting security cooperation in key regions and fields. On the other hand, the U.S. has been ambiguous about its own responsibilities, advocating more for "shared burden" and "shared responsibility" between the U.S. and Japan, without emphasizing the shared values of the alliance, intending to implement a new "offshore balancing" in the Asia-Pacific region, reducing its own investments while relying more on allies to contain China as a competitor, leading to the phenomenon of "empty promises" in alliance cooperation, with verbal commitments exceeding actual deployments. This transformation will have complex impacts on the U.S.-Japan alliance and regional security, and further influence the development of Sino-Japanese security relations.

I. Formation of U.S. Security Policy Toward Japan in Trump's Second Term‌

During his second term, Trump continued to uphold the "America First" philosophy. On one hand, the ranking and management of alliance functions differed significantly from traditional models, with a marked weakening of security cooperation and order maintenance, and a preference for unilateralism and coercive measures in alliance management. In contrast, the previous Biden administration emphasized liberal international order, multilateralism, and non-coercive means. On the other hand, the Trump administration remained committed to strengthening specific regional alliance strategies, aiming to deter adversaries and seek hegemony through strength. As Japan is the most important ally of the United States in the Asia-Pacific region and the key geopolitical security force helping the U.S. contain China, the Trump administration's policies toward the "asymmetric" U.S.-Japan alliance became more complex, reflecting an interweaving of the "Trump Line" and the "Trump Team Line," which together determined the direction of U.S. security policy toward Japan.

‌(1) The "Trump Line" in U.S. Security Policy Toward Japan‌

Trump viewed large alliances as burdensome to the United States, rejecting allies' "free-riding" and even believing that the U.S. was being "extorted" by its allies. He saw his duty as president to correct these errors and secure more benefits for the American people. Based on a merchant mindset and transactional principles, Trump advocated changing the traditional alliance model, unwilling to invest more resources in alliances, instead emphasizing that allies should shoulder greater defense responsibilities in the alliance partnership, aiming for a "balanced alliance." Compared to his first term, Trump's current attitude toward Japan is tougher, emphasizing that the U.S.-Japan alliance must serve U.S. interests. In the economic and trade field, Trump frequently raised issues of reducing the trade deficit with Japan and increasing defense spending, while failing to respond promptly to Japan's proposed negotiation terms.

‌(2) The "Trump Team Line" in U.S. Security Policy Toward Japan‌

The core members of Trump's diplomatic and security team include Secretary of State Marco Rubio, Secretary of Defense Pete Hegseth, and Deputy Secretary of Defense for Policy Elbridge Colby. Unlike Trump's neglect and skepticism, his team members value the role of allies, emphasize the "Indo-Pacific Strategy," and stress strengthening cooperation. They believe that the U.S. strategy of "peace through strength" and "rebuilding deterrence" requires the support of allies. The Trump team's advocacy of "rebuilding deterrence" emphasizes "forward deployment" and highlights the strategic role of the U.S.-Japan alliance in security. The Trump team requires Japan to increase its defense budget, strengthen its own defense capabilities, reduce the loss of initiative in maintaining national security due to excessive reliance on U.S. military power, and play a "force multiplier" security role for the U.S.

In summary, the "Trump Line" does not place much importance on Japan in security strategy but demands that Japan assume greater security responsibilities based on "transactionalism" and the "balanced alliance" principle. The "Trump Team Line," however, adheres to the traditional proactive strategic view of the United States in the Indo-Pacific region and values the U.S.-Japan alliance, requiring Japan to contribute more to security and share security responsibilities with the U.S. from a security strategy perspective.

‌II. Trends in U.S. Security Policy Toward Japan in Trump's Second Term‌

During Trump's second term, the U.S. generally pursued strategic retrenchment, altering its methods and means of maintaining global hegemony and prompting adjustments and transformation in its alliance strategy. Simultaneously, Trump's distinctive diplomatic style and strong dominance over the government have triggered significant adjustments in U.S. security policy toward Japan. For Trump and his team, strengthening the U.S.-Japan alliance by requiring Japan to contribute more within the alliance is a crucial objective of "America First" in U.S.-Japan relations. Under this approach, the Trump team's reinforcement of the U.S.-Japan alliance in the security domain does not contradict Trump's pressure on Japan based on "America First" and his challenges to the U.S.-Japan alliance.

‌(1) Demanding Japan Increase Defense Spending and Pushing It to the Forefront of Indo-Pacific Security Confrontation‌

On one hand, under the concepts of "America First" and "balanced alliance," the Trump administration questioned Japan's "free-riding" on U.S. security, demanding that Japan increase its defense spending, shoulder a greater share of the costs for U.S. troops stationed in Japan, and assume more alliance obligations in the security field. In July 2025, during the preparation for the U.S.-Japan "2+2" talks, the U.S. made informal requests for Japan to raise its defense expenditure as a percentage of GDP to 3.5%. On the other hand, the Trump administration encouraged and required Japan to play a larger role in regional security. On March 4, Colby explicitly stated in response to Senator Roger Wicker's questioning that the U.S. wanted Japan to take on more responsibility in "joint defense of Taiwan." In July, the U.S. Department of Defense further urged Japan to clarify its role in the event of a conflict in the Taiwan Strait.

‌(2) Strengthening Indo-Pacific "U.S.-Japan+" Minilateral Security Cooperation‌

The Trump administration abandoned the traditional "broad alliance" policy, focusing on more flexible and practical minilateral alliances, strengthening Indo-Pacific "U.S.-Japan+" minilateral security cooperation, and deepening the "Indo-Pacific Strategy." First, it emphasized the Quadrilateral Security Dialogue (QUAD) mechanism, making it a priority in U.S. regional policy. Japan is a founding member of the QUAD mechanism and possesses strong strategic coordination capabilities in the "Indo-Pacific Strategy." Second, it reinforced minilateral issue-based security cooperation under the "U.S.-Japan+" framework. On May 31, 2025, the U.S., Japan, and Australia held their first trilateral defense ministerial talks since Trump's re-election, focusing on maritime security and reaffirming the deepening of pragmatic cooperation. On the same day, the U.S., Japan, Australia, and the Philippines held quadrilateral defense ministerial talks. From late May to early June, the U.S., Japan, and South Korea's maritime law enforcement agencies conducted their second joint exercise since June 2024, continuing trilateral coast guard cooperation and strengthening maritime security collaboration. To enhance operational coordination and interoperability, the U.S. advocated absorbing more "like-minded partners" on the basis of past multilateral maritime cooperation successes, expanding the scope and frequency of their participation. Finally, U.S.-Japan cooperation strengthened the Indo-Pacific defense industrial supply chain, enhanced Indo-Pacific security linkage, and increased Indo-Pacific security resilience. The "U.S.-Japan+Philippines" cooperation emphasized trilateral collaboration in the production and application of "Tomahawk" missiles, aiming to strengthen regional joint deterrence and response capabilities. Based on the "Indo-Pacific Industrial Resilience Partnership" (PIPIR), it promoted multilateral defense industrial cooperation in the Indo-Pacific region and facilitated the resilience and stable supply of critical minerals.

‌(3) Strengthening Bilateral Joint Deterrence, Focusing on Economic Security and Defense Industrial Cooperation‌

First, the Trump administration strengthened cooperation with Japan in command and control and joint operations, reinforcing joint deterrence and providing policy support for future coordination and actions by the two countries in regional security. Second, compared to the Biden administration, the Trump administration placed greater emphasis on leveraging Japan's advantages in economic security and technological security, attempting to strengthen economic security and defense industrial cooperation between the two countries. The U.S.-Japan summit joint statement emphasized promoting commercial cooperation between the two countries and significantly increasing bilateral investment and employment levels; enhancing industrial foundations and strengthening cooperation in key technologies such as artificial intelligence, quantum computing, and advanced semiconductors; jointly resisting "economic coercion" and enhancing relevant capabilities; jointly promoting the development of the Indo-Pacific region based on a free and fair economic order, and continuing consultations to further protect critical and sensitive technologies and improve the resilience of supply chains. Finally, the Trump administration required Japan, the world's third-largest shipbuilding country with advanced shipbuilding technology, to provide security cooperation support in the shipbuilding industry. Cooperation between the U.S. and Japan in the shipbuilding sector has become a new focus of defense industrial cooperation between the two countries. Japan has strong independent shipbuilding capabilities, with Mitsubishi Heavy Industries and Japan Marine United skilled in building surface warships, and Mitsubishi Heavy Industries and Kawasaki Heavy Industries skilled in building submarines. The U.S. hopes to strengthen cooperation with Japan in joint production and investment, including co-building merchant ships for military purposes, which can not only promote the revitalization of the U.S. shipbuilding industry but also allow ships deployed in the Indo-Pacific region to avoid frequent returns to their home ports for maintenance and repairs.

III. Objectives of U.S. Security Policy Toward Japan in Trump's Second Term‌

Adhering to the "America First" principle of the "Trump Line," the Trump team selectively adjusts the U.S.-Japan alliance, aiming to respond to great power strategic competition and re-plan the strategic security design in the Indo-Pacific region. Overall, the U.S. security policy toward Japan in Trump's second term pays more attention to the resource input and return on investment of the United States, emphasizing better utilization of Japan's strategic resources to enhance U.S. strength, reduce U.S. strategic overextension, and advocate for Japan to play a greater role in the alliance and regional security, stimulating Japan's strategic potential to better cooperate with and support U.S. regional strategic adjustments and strategic competition with China.

‌(1) Increase U.S. Policy Gains and Better Realize "America First"‌

The Trump team implements the "America First" principle in U.S. security policy toward Japan. On January 20, 2025, on the first day of Trump's re-election, he issued the "Priority Items of 'America First'" statement, taking "America First" as the government's foreign strategic tone. In Trump's Asia-Pacific strategy, maintaining the stability of the U.S.-Japan alliance is not crucial to realizing "America First." Trump questions what the U.S. ultimately "gets" from its military, aircraft, ships, and bases in Japan. Currently, the Trump administration emphasizes "opening sources and conserving resources" in managing the costs of the U.S.-Japan alliance. In terms of "opening sources," the Trump administration requires Japan to increase its defense spending and requires the Self-Defense Forces to purchase more U.S. military products. In terms of "conserving resources," the Trump administration is exploring the cessation of the "Enhanced U.S. Forces in Japan" plan promoted during the Biden administration, and halting this project can save approximately $1.18 billion.

The Trump administration attaches importance to its own economic security. In February 2025, the Trump administration's "America First Investment Policy" memorandum emphasized that "economic security is national security" and advocated "ensuring the prosperity and security of the United States." The Trump administration requires Japan to cooperate with and support the U.S. economic security strategy on issues such as key supply chains and technology. In February 2025, the U.S.-Japan summit joint statement emphasized that both sides will enhance their industrial foundations and strengthen cooperation in key technologies such as artificial intelligence, quantum computing, and advanced semiconductors, and continue consultations to further promote the protection of critical and sensitive technologies and improve the resilience of supply chains.

‌(2) Serve U.S. Regional Strategic Adjustments and Rebuild Deterrence in the Indo-Pacific Region‌

Although the United States has generally pursued strategic retrenchment globally in recent years, the Trump team continuously emphasizes the importance of the Indo-Pacific region, striving to adjust the U.S. strategic focus and resources to the Indo-Pacific region, and the "Indo-Pacific Strategy" remains the Trump administration's primary regional strategy. The Trump administration strengthens security cooperation with Japan, aiming to enhance strategic coordination and military interoperability with Japan, and strengthen U.S. strength and deterrence in the Indo-Pacific region. The Trump administration advocates rebuilding deterrence in the Indo-Pacific region, mainly taking the following three measures. First, improve the posture of forward-deployed forces and promptly upgrade the functions and efficiency of the U.S. Forces Japan headquarters to effectively respond to constantly changing threats. Second, help allies and partners strengthen their defense capabilities. Increase cooperation with Japan in joint deterrence, command and control system upgrades, Asia-Pacific forward presence, joint military exercises, and defense technology fields, maintaining U.S. security participation in the Asia-Pacific region. Third, rebuild the U.S. defense industrial base, cooperate with Japan to enhance theater maintenance capabilities and reduce dependence on long-distance supply chains to strengthen security resilience.

(3) Mobilizing Japan's Military Potential and Geostrategic Coordination Capabilities to Jointly Contain China‌

The United States intends to leverage Japan's military strategic resources, strengthen the U.S.-Japan alliance, implement minilateral balancing, and enhance regional deterrence. Since the postwar period, Japan has long adhered to the "Yoshida Doctrine" of "economic priority, military lightness," with annual defense spending consistently controlled below 1% of GDP, despite its strong economic power and military potential. Moreover, postwar Japan has long cultivated security cooperation with regional countries, providing a strategic foundation for closer U.S.-Japan collaboration.

During Trump's second term, the United States has continued to adhere to a long-term, systematic strategy of competition with China. Trump's strategic retrenchment does not mean that the United States will retreat into traditional isolationism, but rather advocates withdrawing from international burdens and geopolitical conflicts to concentrate resources on countering China. Japan, as a geographically proximate neighbor with unresolved island disputes, emerges as a pivotal partner in this endeavor.

The Trump administration has increasingly encouraged Japan to take a more assertive role in challenging China, including continued collaboration on the "Taiwan card." In the U.S.-Japan summit joint statement, the United States reaffirmed that the U.S.-Japan Security Treaty applies to the Diaoyu Islands, opposes any actions undermining Japan's peaceful control over them, and pledged to use all means—including nuclear capabilities—to support Japan's defense. The statement also expressed concerns over East China Sea and South China Sea tensions, emphasized the importance of maintaining stability in the Taiwan Strait, opposed unilateral actions altering the status quo, and supported Taiwan's more active participation in international organizations. These moves underscore the explicit intent to align Japan with U.S. efforts to contain China. U.S. officials, including Defense Department advisor Oriana Skylar Mastro, have explicitly stated that Japan is the primary U.S. ally to rely on in the event of a Taiwan contingency.

IV. Evaluation of the Impact of U.S. Security Policy Toward Japan in Trump's Second Term‌

Under the backdrop of strategic retrenchment and inward-looking tendencies, the United States has shown a weakening willingness and capability to invest in the U.S.-Japan alliance, with its commitments to security cooperation with Japan being more rhetorical than substantive. The U.S.'s tough stance on tariffs against Japan has further exacerbated Japan's suspicions and concerns about the United States, pushing the U.S.-Japan alliance into a new phase of "drifting" and instability. Simultaneously, under the goals of strengthening the "Indo-Pacific Strategy" and countering China, the United States has selectively engaged in security cooperation with Japan, placing greater emphasis on Japan's role in security within alliance management, inevitably leading to a transformation of the U.S.-Japan alliance in new ways. Out of concerns that the increasing "uncertainty" from the United States may bring negative impacts on itself, Japan is not only proactively strengthening its own security capabilities and the U.S.-Japan alliance but also adopting more complex policies to hedge against these risks.

(1) Will Undermine the Power Structure of the U.S.-Japan Alliance and Accelerate Alliance Transformation‌

First, the Trump administration's demands for Japan to increase its defense budget and strengthen its own military capabilities will promote Japan's rising status within the alliance, prompting changes in the internal structure of the U.S.-Japan alliance. Japan's growing power and changing role within the alliance will affect the traditional power structure of the post-war U.S.-Japan alliance, bringing new shocks to the alliance's stability from within. Second, the Trump administration's "America First" policy and its rhetoric and actions that deviate from the alliance have brought more uncertainty to Japan's security dependence on the United States, leading to enhanced Japanese suspicions and a desire for detachment. Finally, the Trump administration's "security empowerment" of Japan will accelerate Japan's pursuit of "strategic autonomy" during the strategic transition period, fundamentally challenging the U.S.-Japan alliance.

(2) Will Increase the Risk of Regional Conflicts and Exacerbate Security Mistrust‌

First, the United States' joint efforts with Japan to strengthen security cooperation in the Indo-Pacific region and tighten minilateral alliances will intensify regional geopolitical conflicts and disputes. The U.S.-Japan focus on reinforcing the maritime security alliance and leveraging maritime hotspot disputes to enhance deterrence and intervention capabilities in the region will undoubtedly increase the risk of regional confrontation. Second, the U.S. policy of "rebuilding deterrence" by pushing Japan to the forefront of Asia-Pacific security has made Japan more eager to play an active security role within the alliance and the region, further leading to a lack of security trust and increased security risks. Japan is demonstrating its importance to the U.S.-Japan alliance at the cost of regional peace. Finally, stimulating Japan to propose new regional security tasks for the U.S.-Japan alliance will further complicate the regional security situation. To strengthen the U.S.-Japan alliance and prevent being "abandoned," Japan actively exaggerates regional security risks and proposes new regional security cooperation concepts, which will deepen the "alliance dilemma" and increase the risk of the United States being drawn into regional conflicts.

‌(3) Will Complicate Sino-Japanese Security Relations‌

First, it will lead Japan to intensify its involvement in the Taiwan issue to strengthen the U.S.-Japan alliance, undermining the political foundation of Sino-Japanese relations. Japan regards the Taiwan issue as a dual lever to reinforce the U.S.-Japan alliance and contain China. Japan believes that the Taiwan issue is a crucial practical bond for maintaining the U.S.-Japan alliance; without it, the value of the alliance would be significantly undermined, and the U.S. security commitment to Japan would be harder to fulfill. Second, it will enhance Japan's tendency to adopt a balancing approach in its security diplomacy toward China. Under the "America First" principle, Trump's reconstruction of "deterrence" and reinforcement of the "Indo-Pacific Strategy" have elevated Japan's security role in countering China in the Asia-Pacific region, increasing Japan's concerns about being drawn into a conflict or even war with China. Although Japan hopes to join the U.S. in containing China, it still hopes that the U.S. will take the lead in responding to China. Considering the "uncertainty" of the U.S. and the complexity of its own economic security interests, the Japanese government has proposed a dialogic regional security cooperation concept toward China. Finally, it will challenge the economic security relationship between China and Japan. Although Japan's intention to cooperate economically with China has increased against the backdrop of the U.S. tariff war, Japan's tendency to follow the U.S. in economic security and strengthen its vigilance against China will also intensify.

Conclusion‌

Since Trump's second term, the U.S.-Japan alliance has not yet experienced a "rift" similar to that in the Atlantic alliance. Despite facing certain challenges from the "Trump Line," the strategic path and alliance division have shifted from substantial U.S. security strategic asset investment to requiring allies, particularly Japan, to contribute more. Japan is expected to play a more proactive and robust role in security matters. However, the strategic design still centers on strengthening the "Indo-Pacific Strategy" through the U.S.-Japan alliance and maintaining a forward deterrence posture toward regional countries. For Japan, the U.S.-Japan alliance is not a security increment but a security foundation. Consolidating the alliance with the United States and enhancing the credibility of deterrence are Japan's pragmatic policy choices. Japan's diplomatic and security circles even propose that strengthening partnerships with other "like-minded" countries under Trump's second term is not a hedging strategy against the so-called "decline" of the United States, nor should it be interpreted as Japan's move to detach from the U.S. Instead, it should be viewed as a tool for Japan to enhance the strength of the alliance. Most Japanese perspectives hold that if Sino-U.S. relations are repaired without Japan's knowledge, it will be a dangerous moment for Japan, as China is likely to adopt a tough stance toward Japan. The way to avoid this situation is for Japan to vigorously strengthen the U.S.-Japan alliance. (Author: Meng Xiaoxu, Research Fellow at the Institute of Japanese Studies, CASS)

(AI translation, with omission)