A New Phase in the Japan-U.S. Alliance: Increased Production of SM-3, Development of Pacific Defense Bases, and a Turning Point in Northeast Asian Security

In March 2026, President Trump and Prime Minister Sanae Takichi met in Washington, marking the opening of a new chapter in the Japan-U.S. alliance. The agreements reached during the meeting go beyond mere diplomatic rhetoric, indicating a substantial deepening of military and defense cooperation that could fundamentally change the security structure in Northeast Asia.

The most noteworthy outcome of the meeting was the agreement to increase domestic production of the Standard Missile-3 (SM-3) Block IIA in Japan to four times the current level. The SM-3 Block IIA is a sea-based interceptor missile developed jointly by Japan and the U.S. for ballistic missile defense, serving as a key component of a multi-layered defense against ballistic missile threats from China and North Korea. Currently, this missile is jointly manufactured by Raytheon Technologies and Mitsubishi Heavy Industries, but the agreement to increase production is expected to significantly enhance Japan's defense industry's technological capabilities and production capacity. Given that North Korea conducted over 12 ballistic missile launch tests last year, the strategic importance of this decision is clear.

Furthermore, the completion of a feasibility study on the joint production of the AIM-120 Advanced Medium-Range Air-to-Air Missile (AMRAAM) and the expansion of Japan's role in future production were also agreed upon. The AMRAAM is a mainstay in air-to-air combat, adopted by the Japan Air Self-Defense Force, and Japan's participation in domestic production will contribute to strengthening missile stockpiles across allied nations, including NATO, aligning with Japan's defense industrial policy of "export liberalization." Additionally, the two countries confirmed their ongoing close cooperation in the maintenance and operation of the Typhon ground-launched medium-range missile system, which is set to be deployed on the mainland in 2025.

On March 26, the U.S. Department of Defense announced its intention to outsource engine maintenance for F-15 and F-16 fighter jets to Japan. This is not merely a maintenance outsourcing decision; it is a strategic move aimed at improving the operational readiness of U.S. forces stationed in Japan while enhancing Japan's defense technological capabilities. According to reports from the Seoul Economic Daily, the initial focus will be on U.S. military aircraft stationed in Japan, but there is potential for future expansion to include U.S. aircraft deployed in other Asian countries. If realized, Japan would become a major maintenance hub for U.S. military equipment in the Indo-Pacific, gaining both economic and technological benefits while also securing an indispensable role in the alliance.

Significant developments are also ongoing in the Pacific theater. On March 29, Defense Minister Shinjiro Koizumi announced the establishment of a new "Pacific Defense Planning Office (tentative name)" in April, following his attendance at a joint memorial ceremony in Iwo Jima. This new organization aims to fill the gaps in defense coverage over Japan's vast Pacific air and maritime zones, with plans for port development and radar network expansion focused on the Ogasawara Islands. Currently, about 400 Self-Defense Force personnel are stationed on Iwo Jima, but due to the shallow coastal waters, it is difficult for large vessels to dock, and a feasibility study for port development, including the establishment of a fuel and ammunition supply system, is scheduled to begin next year. Japan's defense budget reached 11 trillion yen (approximately $75 billion) last year, and the plan to increase it to over 3% of GDP by 2031 has strong support from the United States.

When viewed integratively, it becomes clear that the Japan-U.S. alliance is accelerating its structural transformation from "Japan being protected" to "Japan actively participating in power projection." Measures such as missile production increases, joint manufacturing, maintenance hub establishment, and Pacific island defense may appear to be incremental changes when viewed individually, but collectively they represent a significant strengthening of deterrence against China in Northeast Asia and are designed to deepen mutual dependence between the U.S. and Japan in times of crisis.

However, there are also numerous challenges. Regarding the issue of amending Article 9 of the Constitution, while the U.S. has not officially stated its position, it is interpreted as having a de facto acceptance. If the exercise of collective self-defense by the Self-Defense Forces is fully constitutionalized through constitutional revision, the regional security environment will change even more significantly, but many countries are increasingly wary of Japan's militarization amid historical recognition issues with South Korea and China. It is essential to remember that stability in Northeast Asia cannot be secured solely through the strengthening of Japan-U.S. deterrence; a balance with diplomatic frameworks that include South Korea, China, and Russia is indispensable.

Takahiro Tanaka (Defense Analyst)