The “Core Problem” for Trilateral Security Cooperation: Challenges for the US-Japan- Korea Relationship

Institutionalizing Trilateral Security Cooperation

On August 18, the leaders of the United States, Japan, and South Korea marked one year since the historic trilateral summit held at Camp David with the release of a new joint statement. The three leaders stressed their “unshakeable belief” that US-Japan-ROK security cooperation “is indispensable for meeting today’s challenges and will set the stage for a prosperous future.” The new statement reflects a continued commitment to maintaining “peace and stability in the Indo-Pacific” by strengthening cooperation between the US-Japan and US-ROK alliances to check the activities of China and North Korea.

Last year’s historic summit promised enhanced strategic coordination between the three countries to bring “security cooperation to new heights.” Over the past year, there has therefore been extensive attempts to institutionalize trilateral defense and security cooperation.

A major step forward was the Trilateral Ministerial Meeting of defense ministers held in Singapore in early June on the sidelines of the Shangri-La Dialogue. Tokyo and Seoul also agreed to resume bilateral defense exchanges and to adopt better communication to prevent the recurrence of a 2018 fire-control radar lock-on incident that undermined bilateral security cooperation. On June 11, Minister of Defense Kihara Minoru then indicated in the Diet that Tokyo and Seoul were considering a first ever Japan-ROK “Two-plus-Two” ministerial-level meeting among the foreign and defense ministers of both countries.

The uptick in trilateral security cooperation continued into July. On July 18, the joint chief of staff of Japan’s Self-Defense Forces and the chiefs of staff of the United States and Korea armed forces gathered in Tokyo for a meeting of top officials of the uniformed services. 10 days later, also in Tokyo, the three defense ministers inked the Memorandum of Cooperation on the Trilateral Security Cooperation Framework. This framework seeks to build on recent developments and “institutionalize” trilateral cooperation, “including senior-level policy consultations, real-time sharing of the DPRK missile warning data, and trilateral exercises.”

Realizing Truly Functional Trilateral Cooperation

The global geopolitical competition between authoritarian and democratic states has intensified over the past decade. In response, the United States and its Indo-Pacific allies, including Japan, South Korea, and Australia, have banded together to assert their shared commitment to defending the values of freedom, the greatest asset for democratic countries. These moves to strengthen trilateral security cooperation among the United States, Japan, and South Korea is a novel attempt to go beyond bilateral alliances and establish a framework that will over time link two key American treaty alliances in Northeast Asia.

An important symbolic step toward this goal was witnessed in late June 2024. The armed forces of the three countries conducted their first ever multidomain trilateral exercise called “Freedom Edge.” The exercise spanned the maritime, air, and cyberspace domains. Based on a plan agreed to in December 2023, the armed forces of all three countries will also establish a trilateral verification system to support the immediate sharing of information on North Korean ballistic missile launches.

However, truth be told, these activities did not necessarily require a high level diplomatic trilateral framework to be implemented. They could have been carried out by the armed forces “naturally” at any time based on the pre-existing capabilities of the three nations’ armed forces. One could therefore say that the tying of the training exercises to the new diplomatic framework was somewhat forced and more of a PR exercise. The three governments will need to deepen cooperation in a much more substantive way, or else the new agreements may ultimately have little practical effect.

As such, there are various practical considerations that are still currently not being addressed by the three capitals. For defense and military personnel, it is still a major problem that there is little effort dedicated to drawing up military plans that would result in truly functional combined trilateral cooperation in the event of a contingency on the Korean Peninsula or in Taiwan. There are also no unit-level training programs being implemented that would enable such coordination to succeed should it be needed.

Only when these more detailed plans and training systems are established and become key operational practices shared by the three countries’ armed forces will the symbolic commitments observed at the various summits be transformed in truly functional trilateral security cooperation. I therefore believe that this is where the Japanese, South Korean, and American military authorities need to focus next.

Going Beyond “Pie in the Sky” Plans

The three governments will have to do a considerable amount of homework to institutionalize security cooperation in a meaningful way. They will need to focus on three particular areas, and they must be willing to examine and adjust strategic concepts and operational plans which have until now been completely untouched.

1. American Power Projection and Strategic Strike Capabilities: US military capabilities in the region are focused on strategic strikes (missile- or air-based attack capabilities) and force projection (the capability to deploy forces in theaters outside the United States). This requires multiple plans to deal with a full range of possible contingencies. 　

2. The US-Japan Alliance: Up until now, strategic concepts and operational plans for the alliance have been predicated on the “sword and shield” division of labor between the United States and Japan. This is where American armed forces have been solely responsible for offensive operations, while the Self-Defense Forces are responsible for defensive operations and rear-area support.

3. The US-ROK Alliance: The current focus of America’s alliance with South Korea has been solely on deterring North Korea, counterattacking if necessary, and defending South Korea.

In addition to these three areas requiring attention, it will be necessary to formulate specific operational plans for combined operations addressing parallel contingencies on the Korean Peninsula and Taiwan. This will be a huge undertaking, and the defense and military authorities of United States, Japan, and South Korea must begin this homework immediately.

After that, the three countries need to work on perhaps the most difficult task—implementing detailed joint training plans based on consistent strategic concepts and improved operational procedures. This will make “on-the-ground” combined operations possible and will ensure the realization of the goal of more robust trilateral security cooperation.

It is therefore notable that the defense ministers of all three countries agreed in the June meeting to conduct a trilateral table-top exercise in the near future. Such an exercise will simulate a contingency on the Korean Peninsula and other regional security challenges, and will require thoroughly examining the joint operational plans of the three countries and the strategic concepts mentioned above. It will involve examining operational plans in an environment that closely resembles a real-life situation and identifying the deficiencies that arise. Subsequently, these deficiencies will need to be addressed while improvements are reflected back into the original plans.

This is a mind-boggling task of substantial complexity. If it is not done properly, and if the work of formulating joint operation plans and adjusting strategic concepts becomes too bureaucratic and detached from front line requirements, the plans will remain little more than “pie in the sky.” Trilateral cooperation will not function in any meaningful way in the event of an actual military contingency.

American Public Opinion: The “Core Problem” Overshadowing All Others

At least two of the three leaders that committed to institutionalizing the trilateral US-Japan-ROK security relationship will no longer be in power by the end of January 2025. The administration of Japanese Prime Minister Kishida Fumio has given way to that of Ishiba Shigeru, while US President Joe Biden also announced earlier this year that he will not run for reelection in November. Therefore, according to one Japanese government official quoted in an August 18 Kyōdō News article, the aim of the one-year joint anniversary statement was “to show that trilateral cooperation will continue even if there is a change in leaders.”

Nevertheless, the United States continues to grow more inward looking. Hardline conservatives in the Republican Party recently opposed and held up the passage of a budget proposal for additional military support for Ukraine despite its still being under attack by Russia. There is also a risk that the election itself will further divide public opinion on foreign policy, making it harder for the White House to commit decisively to using all its force in contingencies involving its allies and Taiwan. This is a major “core problem” that overshadows all the issues outlined above.

The support of the American people is a prerequisite for continued US commitment to maintaining the military balance in East Asia and the Indo-Pacific. This includes support for strengthening security cooperation between the United States, Japan, and South Korea. Tokyo and Seoul not only need to work on promoting support in their own countries for cooperation with each other, but also find ways to increase public support in the United States for American armed forces to continue playing an essential role in East Asian security affairs.

(Originally published in Japanese. Banner photo: the US Navy’s nuclear-powered aircraft carrier Theodore Roosevelt arrives in Busan, South Korea, to take part in the joint US–Japan–South Korea exercise “Freedom Edge,” June 22, 2024. © Kyōdō.)