The United States Fully Supports Japan's Defense Strengthening: A New Horizon for Northeast Asian Security

In March 2026, the U.S. government expressed clear support for Japan's defense capability enhancement, ushering in a new phase of security cooperation in Northeast Asia. This move reflects a strategic intent to assign a more active security role to Japan, the U.S.'s most trusted ally, in a region where China's military expansion and North Korea's nuclear and missile threats intersect.

According to information from the U.S. Department of Defense and diplomatic sources, the U.S. is advancing plans to outsource the maintenance of F-15 and F-16 fighter jet engines to Japan. These aircraft are the mainstay of the U.S. Air Force and its allies, and this decision signifies that the U.S. has chosen Japan as a partner in expanding alliance relations in the defense industrial sector. Initially, the focus will be on U.S. military aircraft stationed in Japan, but in the future, it may also include aircraft deployed in other Asian countries. This arrangement is expected to immediately enhance the readiness and operational rate of U.S. forces in Japan while promoting the development of Japan's related technologies and defense industry.

Furthermore, it is noteworthy that the U.S. is effectively turning a blind eye to Japan's moves toward amending its pacifist constitution. Article 9 of the Japanese Constitution, drafted under the leadership of the Allied Powers, particularly the U.S., after World War II, centers on the renunciation of war and the limitation of military forces. Discussions on constitutional amendments, which have been ongoing since the era of former Prime Minister Shinzo Abe, have accelerated further under Prime Minister Sanae Takaichi. Although the U.S. has not officially expressed support for the amendments, it is widely interpreted that it is tacitly accepting this movement.

Regarding the increase in defense spending, Washington is strongly backing Tokyo's efforts. Japan's defense budget for the last fiscal year was 11 trillion yen (approximately $75 billion), which corresponds to about 2% of its Gross Domestic Product (GDP). Japan plans to raise its defense spending to at least 3% of GDP by 2031. In an official statement from the White House, it was noted, "We welcome Japan's efforts to increase defense spending as part of its rapid enhancement of defense capabilities," and "The U.S. and Japan will deploy advanced capabilities to Japan to build a robust defense posture."

During the Japan-U.S. summit held on the 19th of this month, Washington conveyed its position that Japan should take on a more active security role among allies. Additionally, Japan is scheduled to participate in U.S.-Philippines joint military exercises next month. While these exercises are conducted annually, it will be the first time since Japan's military defeat in World War II that Japanese combat troops will land in the Philippines.

The backdrop of U.S. support for Japan's military enhancement is closely related to changes in the security environment in Northeast Asia. In a region where major countries, including Russia, Japan, and China, converge, Washington is positioning Japan, its ally, as a key cooperative partner to maintain its leadership. Furthermore, with U.S. military forces concentrated in the Middle East and Europe, it has become difficult for the U.S. to lead the security order in Northeast Asia alone as it once did. This situation is interpreted as the reason why Washington has designated Japan as its most reliable partner in the region.

Moon Sung-mook, director of the Korea Unification Strategy Center, pointed out, "Northeast Asia is a region where multiple challenges overlap, including China's military expansion, the Taiwan Strait issue, and North Korea's nuclear and missile issues," and analyzed that "from the U.S. position, which has a delicate relationship with China, it is necessary to work with allies to address security issues in this region rather than solving them unilaterally, and Japan, which is also in a confrontational relationship with China, is strengthening its ties with the traditionally allied U.S."

This series of moves indicates that the Japan-U.S. alliance has entered a new phase. Japan is transforming from a mere recipient of defense equipment to a provider of weapon systems in the region. Through the officially proposed Official Security Assistance (OSA) program in the 2022 National Security Strategy, Japan is considering exporting coastal surveillance radars and transferring Abukuma-class escort ships to enhance the maritime defense capabilities of the Philippines. These measures reflect Japan's intention to form a stronger regional coalition to counter an increasingly assertive China.

At the same time, Japan's planned enhancement of its defense capabilities goes beyond mere modernization of equipment. The Japan Maritime Self-Defense Force currently has 22 submarines, but there are growing calls for rapid expansion to address national and regional threats. In particular, the Taigei-class submarines are evaluated as suitable for providing a "manageable numerical advantage" to strengthen deterrence across the region. Additionally, by 2026, the destroyer Chokai (DDG-176) is expected to be equipped with Tomahawk cruise missiles, taking on a new role as the first vessel with stand-off defense capabilities at sea.

The formulation of Japan's next defense strategy and a new five-year plan is already underway and is expected to be nearly completed by late 2026. To overcome the challenges Japan faces, more active, close, and high-level dialogue is essential. Furthermore, in 2026, the renegotiation of the Special Measures Agreement (SMA) that determines the burden of costs for U.S. forces stationed in Japan is scheduled, which will also serve as a litmus test for Japan-U.S. relations.

Cooperation among the U.S., Japan, and the Philippines is also being strengthened. As gray zone activities in the South China Sea and East China Sea become more active, there are recommendations for the U.S. to continue investing in trilateral cooperation with Japan and the Philippines. The shared sacrifices of generations of Japanese, Korean, and American military personnel have historically prevented large-scale conflicts in Northeast Asia for over 70 years amid significant strategic tensions, and these alliances will continue to be the foundation of regional stability.

The current trend of Japan strengthening its defense capabilities with full support from the U.S. in this "new era of crises" indicates that the security order in Northeast Asia is undergoing fundamental reorganization. This change is altering not only the balance of military power but also the very nature of strategic partnerships in the region.