Download or print as PDF.

Recent developments in modernising the Japan-US alliance highlight the two countries’ willingness to adjust the functions of quasi-public goods in the Indo-Pacific to the rapidly deteriorating security environment. The first meeting of the Japan-US Defense Industrial Cooperation, Acquisition, and Sustainment in June 2024 identified three major areas of bilateral defense industrial cooperation: co-production of missiles, including glide-phase interceptors designed to intercept hypersonic missiles; sustainment of US ships and aircraft; and enhancement of defense supply chain resiliency. Following this meeting, the defense and foreign ministerial meeting, known as “2+2,” in July pledged to upgrade the alliance’s command and control (C2) cooperation. This pledge included the announcement of the United States’ policy direction toward reconstituting US Forces Japan (USFJ) – currently responsible only for administrative functions – as a joint operational force headquarters reporting to the Indo-Pacific Command. The 2+2 meeting also laid out new projects for defense production cooperation, such as expanding the co-production capacity of air-to-air missiles and surface-to-air missiles.

These moves are recognised as efforts to transform the alliance structure from one of coordination to one of integration, and from an isolated composition of the US hub-and-spokes system to a more intertwined component of a region-wide latticework. While this is true, focusing solely on the transformative nature of the alliance can lead to overlooking the unchanged geo-strategic structure that has shaped its roles for about 65 years, since the signing of the Japan-US Security Treaty in 1960.

The historical role of the alliance

The Japan-US alliance has served a dual purpose: the defense of Japan, and the maintenance of peace and security in the Far East, including South Korea, Taiwan, and the Philippines. From the Japanese perspective, the alliance ensures the United States’ defense commitment to Japan in exchange for providing military bases for US forces that may operate throughout the region. On the other hand, from the US perspective, defending the Japanese archipelago – which serves as a shield for the US west coast against continental threats – ensures the security of the US homeland. This was why former Prime Minister Yasuhiro Nakasone compared Japan to “an unsinkable aircraft carrier” against Soviet bombers in 1983. Additionally, US forces stationed in Japan can serve as reinforcements for either the Korean Peninsula or the Taiwan Strait in the event of a contingency. Recognising this strategic importance, former Prime Minister Eisaku Sato stated that the security of South Korea was “essential to Japan’s own security,” and that “the maintenance of peace and security in the Taiwan area was also a most important factor” for Japan’s security in the Joint Statement with President Richard Nixon in 1969.

Addressing complex threats

While these core missions have not fundamentally changed to date, the emphasis and priorities have differed between the two parties, leading to policy discord and fears of entrapment in the past. What has changed is the growing military threats from continental powers, especially China, exacerbated by North Korea’s military advancement. These growing threats have blurred the distinction between the two missions of the alliance, namely, the defense of Japan and the maintenance of peace and security in the region, and created a relationship in which enhancing one mission strengthens the other. As a result, convergence of interests, rather than divergence, has become a defining characteristic of the alliance.

The relative decline of US military power and the increasing entanglement of Japan’s security with that of other areas in the region make the effective use of the alliance’s aggregate defense capabilities essential. In the past, individual services of the US forces in Japan could be dispatched separately to the main conflict zone, either as ground and air components on the Korean Peninsula or as a carrier strike group near Taiwan. Some elements of the Japanese Self-Defense Forces (SDF), such as anti-submarine warfare and mine-sweeping fleets, could play a supporting role, while the main body, including ground and anti-air units, ensured the defense of Japan. Real joint operations among service components were not a prerequisite in the past. However, as the potential theater expands due to the development of Chinese power projection and missile capabilities (as well as North Korea’s missile capabilities), such patchwork operations have become untenable. This development is the main reason why the restructuring of C2 within USFJ and closer coordination with the SDF’s C2 are now strongly recognised as priorities.

In addition, because US forces in the Western Pacific and the SDF are outnumbered by Chinese forces (at least in terms of quantity), increasing the efficiency and readiness of currently operating forces is vital, alongside efforts to steadily beef up future capabilities. Defense co-production and the maintenance of US assets in Japan can serve this end.

Ultimately, the possibility of multiple contingencies becoming entangled forms the foundation of the intertwined latticework of security cooperation in this region. In such a highly complicated environment, refraining from cooperation is not a luxury that alliance members can afford. The recent announcements by Japan and the United States are merely interim reports on the future evolution of the alliance, leaving major challenges unresolved – for example, the newly appointed three-star general of the joint force USFJ may face difficulty in controlling the Commander of the Seventh Fleet, who holds the same rank. Addressing these challenges will carry over to the next US administration. Still, pinning down the direction of their efforts may signal the resolve of the two countries to upgrade the alliance, not only in response to potential threats but also to reassure their mutual partners in the region.

About the Author

Hirohito Ogi is a senior research fellow at the Asia Pacific Initiative (API) & the Institute of Geoeconomics (IOG), the International House of Japan (IHJ).

The opinions articulated above represent the views of the author(s) and do not necessarily reflect the position of the Asia-Pacific Leadership Network or any of its members. APLN’s website is a source of authoritative research and analysis and serves as a platform for debate and discussion among our senior network members, experts, and practitioners, as well as the next generation of policymakers, analysts, and advocates. Comments and responses can be emailed to apln@apln.network.

Image credit: David Tran, iStock