Interviews | Diplomacy | East Asia

Insights from Jeffrey Hornung.

U.S. President Donald Trump welcomes Japanese Prime Minister Takaichi Sanae to deliver remarks to Yokosuka Naval troops aboard the USS George Washington at Yokosuka Naval Base, Japan on Oct. 28, 2025.

Credit: Official White House Photo by Daniel Torok

The Diplomat author Mercy Kuo regularly engages subject-matter experts, policy practitioners and strategic thinkers across the globe for their diverse insights into U.S. Asia policy. This conversation with Dr. Jeffrey Hornung – Japan Lead at the National Security Research Division, senior political scientist at RAND Corporation, and co-author of the RAND report “U.S.-Japan Alliance Under New Management” – is the 486th in “The Trans-Pacific View Insight Series.”

**Identify vectors of continuity and change in Japan-U.S. security and economic relations. **

There are several areas of continuity in the U.S.-Japan alliance that often go unnoticed. In the economic domain, Japan continues to play a role as a guardian of the free and open Indo-Pacific order while advocating for formal multilateral initiatives, like the CPTPP [Comprehensive and Progressive Agreement for Trans-Pacific Partnership]. And while the United States continues to eschew participation in the CPTPP, as it has for years, it does continue to champion many of the same issues that Japan does. The U.S. and Japan work together in several of these areas. This includes supply chain resilience, de-risking economies, and looking to partner with like-minded countries in critical technology sectors.

In the security domain, the two continue to prioritize the alliance and partnership with one another as a means to counterbalance and deter China. While Japan has also worked to build layers of security frameworks that are not solely dependent on the United States, this is a trend that started well-before the current administration but continues to be supported by Washington.

The changes in bilateral ties have dominated the headlines and are best summarized as economic matters now taking precedence over traditional security issues. Whether it be the allies taking a different approach to the rules-based trade order and the use of tariffs or their views on how to secure production networks and address trade differences, the allies’ differences are often more visible than the continuities mentioned above.

There is less change in the security domain with the possible exception of how both countries view the value of foreign aid. While it is easy to say Washington’s demands for more defense spending is a change, this is not a new aspect of the alliance relationship (even though the percentage requested may be).

Importantly, as the recent Trump-Takaichi summit has shown, bilateral ties appear strong, buttressed by a personal relationship between the two leaders. Given this relationship, it is likely that the two countries will be able to overcome any potential friction caused by the changes in policies.

Examine five areas the Japan-U.S. alliance could leverage to shape Indo-Pacific regional dynamics.

Considering the changes and continuity, the U.S.-Japan alliance continues to benefit the peace and stability of the Indo-Pacific region. There are five areas in particular that could pay dividends if leveraged.

The first area is capacity-building of regional states. Through the allies’ public financing and similar initiatives, the allies’ support helps regional countries contribute to greater regional peace and stability by enhancing those countries’ capabilities.

The second area is the deepening of minilateral groupings in which the United States and Japan are core members. Although there has been no active push in minilateralism in recent months, they still exist and the alliance could find new and innovative ways to leverage them to meet shared challenges and address common interests.

A third area is responding to countries in need. Japan remains a major international aid donor and until 2024, the United States was the world’s leading donor of humanitarian assistance and development aid. Although the Trump administration shut down the U.S. Agency for International Development, it has realigned certain functions to the State Department, perhaps enabling greater cooperation in those areas of aid where the objectives of the two align.

The fourth area is energy security. Both countries share a common interest in energy security, allowing them to deepen their cooperation on current energy supplies and transitions to clean energy sources while diversifying their supply chains for critical minerals, mining, and energy technologies. This could include not just procurement but developing and promoting new technologies to diversify their options and use their current supplies more efficiently.

The final area is defense industrial cooperation in co-production, co-development, and co-sustainment of defense equipment and technologies. Not only does expanded cooperation provide both allies with access to pooled resources for development of new defense equipment, it also provides the United States with access to short-term maintenance on U.S. Navy ships in Japanese shipyards, mirroring the type of maintenance that U.S. military aircraft already receive in Japan. It also could help bolster stockpiles of critical weapons.

**Explain the strategic relevance of Japan-U.S. minilateral groupings in the absence of a formal Indo-Pacific security framework. **

With the lack of any formalized security framework in the Indo-Pacific region that is equivalent to NATO, the United States has historically relied on its separate bilateral alliances to pursue specific policies. In recent years, the United States has successfully deepened – and in some cases established – several minilateral arrangements that are centered around U.S. treaty allies. Although the motivation for their respective establishments varies, a common thread in recent years is a mutual concern about China. Importantly, the United States and Japan are central to these arrangements.

Because these groupings are centered on common interests and provide agility and adaptability to enable partners to address specific issues that arise, the alliance is able to respond to regional issues in a quick, ad-hoc manner if needed while leveraging broader partner capabilities.

**In what ways can the Japan-U.S. Energy Security Dialogue advance U.S. energy security priorities? **

The Japan-U.S. Energy Security Dialogue provides the allies an opportunity to discuss cooperation to strengthen energy security, accelerate clean energy transition, and diversify supply chains for critical minerals and clean energy technologies. Understanding that U.S. priorities may be different today than they were when the last iteration was held in 2024, the venue still provides an opportunity to collaborate on energy security and find ways to reduce their shared vulnerabilities to their global supply chains dominated by China. Japan and the United States can work together to cooperate on energy supply chains and critical minerals and promote innovative technologies in areas of shared importance while addressing current U.S. energy security priorities.

**Assess the domestic political challenges facing Tokyo and Washington and implications for advancing the Japan-U.S. alliance. **

The challenges facing the allies are very different but nevertheless carry implications for the alliance.

In the United States, President Donald Trump continues to focus on a broad-ranging agenda that is not universally supported domestically and at a pace that some find disruptive. This includes securing the southern U.S. border, reducing the size of the federal government, finding ways to end the wars in Ukraine and Gaza, and promoting an ambitious domestic economic agenda that has involved leveling economic tariffs on U.S. trading partners.

Importantly, with the exception of his recent trip to the Indo-Pacific, there has yet to be a policy focus on the region. Not only is there still no National Security Strategy or National Defense Strategy, there has been no discussion of an Indo-Pacific strategy or China strategy, meaning there is no detailed vision of where Japan fits in U.S. strategy or how the alliance can be leveraged toward broader regional objectives.

Additionally, lauding the alliance on one hand and then leveling tariffs and expecting increased defense contributions on the other mean there is no consistent message to Japan, which leaves the potential open for friction.

The challenges facing Prime Minister Takaichi Sanae are also domestic and revolve around political issues. Unlike her predecessor, Takaichi is enjoying extremely high approval ratings. But because her party lost two major elections, her administration needs to shore up voter trust. This will require a dedicated effort on bread-and-butter issues, not geopolitical issues or defense initiatives.

While she has already started a revision of three major strategic documents and hosted a widely-lauded summit with President Trump, any effort that is seen as neglecting those domestic bread-and-butter issues could hurt her support rate and lead to more voters turning away from her party. Should that happen, her administration could be short-lived. This could limit the political capital of the Takaichi administration to advocate new initiatives if she is not seen as addressing those domestic issues as well.

Collectively, these challenges point to a situation where Japan and the United States have strengths and appear to be in alignment on strategic issues, but the ability to leverage those advantages toward common goals might prove difficult.