A New Phase in the Japan-U.S. Alliance: The Takai Administration's Promotion of Defense Industry Integration and the Reorganization of Security in Northeast Asia

In March 2026, the Japan-U.S. alliance is reaching a historic turning point. The Japanese government, led by Prime Minister Sanae Takaichi, has announced further enhancements following the achievement of a defense budget equivalent to 2% of GDP. In close coordination with the Trump administration in the United States, the division of security roles in Northeast Asia is being fundamentally re-evaluated.

According to a report from the Seoul Economic Daily (English version) dated March 26, the U.S. Department of Defense has decided to commission Japan for the maintenance of F-15 and F-16 fighter jet engines. This decision goes beyond mere maintenance cooperation and fundamentally changes Japan's position within the U.S. defense industrial alliance. While prioritizing the fighter jets of the U.S. forces stationed in Japan, there is also a suggestion that aircraft deployed to other Asian countries may be included in the future. This measure is analyzed to immediately enhance the readiness and operational rate of the U.S. forces in Japan, while also directly contributing to the strengthening of Japan's defense industry's technological capabilities.

From the perspective of defense spending, Japan's defense budget for fiscal year 2025 is expected to reach 11 trillion yen (approximately $75 billion), which corresponds to about 2% of GDP. The Takaichi administration plans to further increase this, aiming for over 3% of GDP by 2031. The United States has explicitly expressed support for this initiative in an official White House statement, indicating a de facto approval of Japan's rearmament policy.

In terms of enhancing the capabilities of the Japan Air Self-Defense Force and the Japan Maritime Self-Defense Force, an analysis by National Interest magazine is noteworthy. The magazine argues that the Japan Maritime Self-Defense Force should build a deterrent force based on its existing 22 "Taihei" class submarines, creating an "Affordable Mass" of deterrence. The Taihei class is equipped with an air-independent propulsion (AIP) system and is considered an essential force to counter the rapid underwater military buildup of the Chinese Navy. The expansion of submarine capabilities is not merely a numbers game; it is also a strategic necessity to secure undersea dominance from the East China Sea to the southwestern islands.

The economic and security integration between Japan and the United States is also significantly deepening. As a result of the U.S.-Japan summit in March 2026, the two countries announced a second investment package based on the "2025 U.S.-Japan Strategic Trade and Investment Agreement." This includes a maximum investment of $40 billion for the construction of small modular reactors (SMRs) in Tennessee and Alabama by GE Vernova and Hitachi, as well as a maximum investment of $33 billion for natural gas power facilities in Pennsylvania and Texas. These investments are not purely economic projects; they strongly reflect security intentions related to energy security and supply chain resilience.

Cooperation in the space domain is also rapidly expanding. According to an analysis by CSIS (March 2026), Japan's Ministry of Defense plans to begin integrating space-related functions from fiscal year 2026, moving towards centralizing responsibilities that have been dispersed across policy-making and procurement. The U.S. Department of Energy and Japan's Ministry of Education, Culture, Sports, Science and Technology have signed a statement of intent for cooperation on AI-driven scientific exploration and high-performance computing, indicating that Japan-U.S. collaboration in technological security is extending beyond the military domain.

Regarding the issue of amending Japan's pacifist constitution, while the United States has not officially expressed support, experts generally agree that it is effectively being tacitly accepted. The pacifist constitution, centered around Article 9, was established under the leadership of the Allied powers after World War II, and the very discussion of its amendment symbolizes a structural change in Japan-U.S. relations. The movements under the Takaichi administration can be seen as an acceleration of the trajectory that began during the Abe administration, resulting from the convergence of U.S. pressure for "burden-sharing" and Japan's aspiration to be a "normal country."

In the security environment of Northeast Asia, where the threats of North Korea's nuclear and missile capabilities and China's military rise are converging, the expansion of Japan's role is becoming an inevitable trend. Defense analyst Daiki Tsuboi, writing for the Indo-Pacific Defense Forum, points out that "Japan must continuously strengthen its indispensability," arguing for deeper defense integration, expanded access to facilities, and robust defense spending.

The most important implication of this series of movements is the direction towards "breaking away from the asymmetrical alliance between Japan and the U.S." The Japan-U.S. security framework established during the Cold War had an asymmetrical structure where the U.S. provided the "shield" and Japan provided the "base." However, the ongoing changes indicate that Japan is taking on higher capabilities and responsibilities, transitioning towards a more symmetrical partnership. The commissioning of F-15/F-16 engine maintenance is a symbolic step in this direction, elevating Japan from a "maintenance base" to a "strategic industrial partner" in terms of the defense industry.

If the defense budget reaches 3% of GDP by 2031, Japan's annual defense budget would amount to 16 to 17 trillion yen, comparable to levels seen in the UK and France. This could have a decisive impact on the balance of power in Northeast Asia. How defense cooperation with regional partners such as South Korea, Australia, and the Philippines unfolds will be key to regional security in the coming years. The Japan-U.S. alliance is evolving into a core element of a multi-layered architecture supporting the Indo-Pacific order, no longer merely a bilateral security treaty.