The Japan-U.S. Alliance After the Trump-Takaichi Summit: Challenges Facing the Deepening of Strategic Cohesion

On March 19, 2026, the summit meeting between President Trump and Prime Minister Sanae Takaichi in Washington became a symbolic event representing the current state of the Japan-U.S. alliance. Held against the backdrop of the crisis in the Middle East due to the Iran-Israel war, this meeting has been evaluated as focusing more on "avoiding serious rifts" than on concrete breakthroughs. However, behind the meeting, structural changes are underway that fundamentally shake the security environment in Northeast Asia.

Prime Minister Takaichi clearly rejected Japan's Self-Defense Forces' request to be dispatched to the Persian Gulf. This is a natural conclusion when viewed in light of the legal interpretation based on the 2014 security legislation. Japan is permitted to use force only in situations where "the existence of our country is threatened," and contributing to the safety of navigation in the Strait of Hormuz does not meet this threshold. The unique premise of constitutional constraints in Japan clashes directly with the Trump administration's demand for "allies to bear more burdens." However, to avoid this rejection being perceived as "disloyalty to the alliance," Tokyo has balanced its diplomacy by proposing alternatives such as strengthening energy security cooperation, expanding imports of U.S. energy, and improving stockpiling systems.

A more important issue lies in the consistency of Japan and the U.S.'s strategic recognition regarding the Taiwan Strait and China. The joint statement from the summit specifically named China, yet intentionally kept references to the Taiwan issue modest. The Takaichi administration had suggested in November 2025 that a Taiwan emergency could qualify as a "situation threatening existence," but under increasing diplomatic pressure from China, Tokyo had no choice but to carefully adjust its expressions. This stance highlights the biggest dilemma in Japan's defense strategy: the contradiction between economic interdependence with China and the recognition of security threats.

In terms of defense spending, Japan is advancing ambitious goals ahead of schedule. The 2022 defense buildup plan aimed to raise defense spending to 2% of GDP by 2027, but the Takaichi administration has moved this target up to 2026. On March 31, 2026, the deployment of the Type 25 surface-to-ship guided missile (SSM) with a range of 1,000 kilometers and the Type 25 high-altitude, high-speed guided missile (HVGP) with a range of several hundred kilometers began. These long-range stand-off weapons have the potential to fundamentally change the defense posture of the southwestern islands. However, there is a gap between the deployment of weapons and the actual operational capabilities, with challenges such as ammunition stockpiling, personnel training, and the integration of command and control systems remaining.

An analysis report published by CSIS in April 2026 evaluates the strategic coherence of the Japan-U.S. alliance across six areas: alliance coordination, deterrence and response capabilities, defense industrial base cooperation, cybersecurity and information sharing, burden sharing, and partnership and coalition building. While the report assesses that cooperation at the operational level is progressing relatively smoothly, it points out that the lack of a strategic vision to guide the alliance's priorities is the biggest obstacle. This suggests an inherent directional misalignment between the Trump administration's "America First" policy and Japan's "proactive pacifism."

The Takaichi administration plans to update three strategic documents—the National Security Strategy, the National Defense Strategy, and the Defense Buildup Plan—by the end of 2026. These revisions are expected to further advance the recognition established in the 2022 version that positioned China as the "greatest strategic challenge." Particularly noteworthy is the strengthening of Japan's unique defense industrial base and the expansion of frameworks for defense equipment transfer and joint development with the U.S. In areas such as missile joint development, cooperation in emerging technology fields, and the establishment of critical mineral supply chains, Japan-U.S. cooperation in economic security is entering a new phase.

Factors on the U.S. side are also bringing uncertainty to the alliance. U.S. military operations in Venezuela and Iran raise questions about the sustainability of U.S. forward deployment in the Indo-Pacific. For Asian allies, the possibility that military intervention in the Middle East could dilute deterrence in the Far East is a serious concern. The U.S. National Security Strategy published in December 2025 prioritizes the Western Hemisphere, followed by addressing the China challenge in the Indo-Pacific, but it remains unclear whether actual resource allocation will reflect this priority.

The most realistic strategy Japan can pursue is to steadily improve its self-defense capabilities while deepening trilateral cooperation with Australia, India, South Korea, and the Philippines, all within the framework of the alliance. In fact, the Takaichi administration has been increasing bilateral and multilateral exercises with these partners, and the construction of a networked security cooperation is steadily progressing. Mechanisms for information sharing among Japan, the U.S., and South Korea, defense equipment cooperation between Japan and Australia, and maritime security cooperation between Japan and the Philippines are beginning to function as elements that expand Japan's strategic options.

The security environment in Northeast Asia is under triple pressure from the intensification of China's coercive actions in the East China Sea and South China Sea, the continued development of North Korea's nuclear and ballistic missile capabilities, and the protraction of the Russia-Ukraine war. For the Japan-U.S. alliance to continue functioning in this environment, it is essential to deepen substantive defense cooperation while managing the tension between the Trump administration's transactional diplomacy and Japan's cautious constitutional interpretation. The Takaichi administration's updates to the three strategic documents will likely be the first test to directly address this challenge.