What the Large-Scale Reorganization of the Japan Self-Defense Forces and the Realignment of the U.S. Air Force in Japan Mean: How Dual Military Transformations Redefine the Security Environment in Northeast Asia

In late March 2026, Japan's security system reached a historic turning point. Almost simultaneously with the Japan Self-Defense Forces (JSDF) implementing the largest organizational adjustment since the formulation of the new "National Security Strategy" in 2022, the U.S. Air Force's 5th Air Wing began a fundamental reform of its command structure and the deployment of F-35A aircraft at Misawa Air Base. This dual transformation, in which both Japan and the United States are advancing military restructuring in a clearly interconnected manner, could have profound implications for the security environment in the Northeast Asia region.

The Japan Maritime Self-Defense Force's "Surface Fleet Revolution" is the most noteworthy change within this reorganization. On March 23, the JMSDF conducted its largest organizational restructuring since its establishment, abolishing the traditional escort fleet and creating a new surface fleet. Under the new formation, surface combat groups from the 1st to the 3rd, amphibious warfare and mine warfare groups, and a patrol defense group have been integrated under the direct control of the Self-Defense Fleet. This reorganization indicates a clear intention to centrally manage the previously dispersed major surface combat capabilities and aims to "flatten" the command structure. Particularly noteworthy is the establishment of the amphibious warfare and mine warfare group. This signifies a capability build-up specialized in island defense, route control, and maritime maneuver operations, and it must be said that this organization is strongly conscious of potential situations in the southwestern islands. Additionally, the deployment of the latest "Mogami" class escort ships to the patrol defense group, which are already engaged in actual missions, underscores the speed of implementation.

The Japan Air Self-Defense Force's transition to the space domain is also significant. With a name change to "Aerospace Self-Defense Force" planned by the end of fiscal 2026, the space operations group was elevated to a space operations squadron on March 23. The personnel increased from about 310 to approximately 670, and further reorganization into a "Space Operations Group" (tentative name) with a scale of about 880 personnel is planned within the year. The phased approach of "expanding first, then elevating, and finally changing the name" is not merely a change of signage but a manifestation of the intention to genuinely expand the operational domain from air to space.

In the Japan Ground Self-Defense Force, the establishment of a new logistics support school through the integration of multiple rear support schools, the reorganization of the Supply Control Headquarters into the Supply Headquarters, and the confirmation of the establishment of an information operations unit have been noted. Officially referred to as "information warfare response" and "counter-disinformation measures," this suggests the construction of multifaceted information operational capabilities, including cognitive domains, within the framework of integrated operations.

On the other hand, the transformation of the U.S. Air Force in Japan is also progressing rapidly. The reform of the 5th Air Wing directly addresses the long-criticized inefficiencies in the command structure. Traditionally, the operational command authority of the U.S. Air Force in Japan belonged to the Pacific Air Forces' 613th Air Operations Center in Hawaii, requiring approval across the Pacific for frontline unit actions. With this reform, a new Air Operations Center subordinate to the 5th Air Wing has been established at Yokota Air Base, granting autonomous operational authority for tactical forces in small-scale conflicts. Additionally, the establishment of a dedicated air defense operations command squadron and an information processing and coordination mechanism, as well as the decision to transition the 5th Air Wing commander from a dual-hatted position with the U.S. Forces Japan commander to a dedicated role, have been made. As a result, the 5th Air Wing is set to transform into a central hub for conducting multi-domain integrated operations in air, space, and cyber in the Indo-Pacific region.

Equipment updates at Misawa Air Base are also steadily progressing. On March 28, the first four of 48 F-35A fighters, as part of a plan to update the 36 F-16 fighters of the 35th Fighter Squadron, arrived. These aircraft, transferred from Hill Air Force Base in Utah (three aircraft) and RAF Lakenheath in the UK (one aircraft), have been incorporated into the 13th Fighter Squadron, followed by the 14th Fighter Squadron also undergoing a type conversion, ultimately completing a two-squadron F-35A structure. At Kadena Air Base, the update from F-15C/D to F-15EX is ongoing, and at Iwakuni Air Base, the expansion of F-35B deployment is also in progress, indicating a comprehensive modernization of the U.S. Air Force in Japan.

However, this dual transformation also encompasses serious challenges. First, while the functions of the 5th Air Wing have significantly expanded, there has been no corresponding increase in troop levels. There are concerns about the risk of overburdening missions and insufficient support capabilities. Second, there is the issue of strategic asymmetry between Japan and the U.S. Under the Trump administration's "America First" policy, the U.S. has sought a greater burden of defense costs from Japan while strictly managing operational command authority. This fundamentally contradicts Japan's goal of pursuing strategic autonomy and enhancing its influence in the region through the large-scale reorganization of the Self-Defense Forces. Building true integrated operational capabilities that go beyond routine joint training and information sharing may be difficult within this "same bed, different dreams" alliance structure.

Japan's defense-related budget for fiscal 2026 is expected to reach approximately 9.04 trillion yen (about 56.6 billion dollars), serving as the foundation for these organizational reforms and equipment construction. In a press conference on April 10, the Defense Minister cited Secretary Hegseth's confirmation that, despite the escalating tensions in the Middle East, "there will be no changes to the posture of U.S. forces in Japan," indicating that there would be no impact on the alert and surveillance posture around our country. However, this statement itself paradoxically highlights the existence of concerns about the potential impact of military actions in the Middle East on U.S. forces in Japan.

In conclusion, the military transformations of both Japan and the U.S. reflect a fundamental change in the security paradigm in Northeast Asia, going beyond mere organizational restructuring. The JSDF's transition to "integrated operations" and the U.S. forces' shift to a "forward operational command center" are clear indications of preparations based on the assumption of high-intensity conflicts. A cold strategic judgment is required to ensure that the Japan-U.S. alliance, which should aim for regional stability and tension reduction, does not inadvertently accelerate a chain of arms races.