The Path of U.S.-South Korea-Japan Cooperation: Strengthening Trilateral Relations Amid Uncertainty

Key Chapter Title List

1. U.S.-South Korea-Japan Trilateral Cooperation: Past, Present, and Future
2. How to Consolidate U.S.-South Korea-Japan Cooperation Under New Leadership Changes
3. Beyond Historical Memory: South Korea's Internal Divisions and U.S.-South Korea-Japan Trilateral Cooperation
4. Beyond Security: Human Rights as a Foundation for Japan-South Korea Cooperation
5. Addressing Uncertainty: Risk Management in U.S.-South Korea-Japan Trilateral Cooperation
6. U.S.-South Korea-Japan Economic Security Cooperation: Clarifying Resilience, Competitiveness, and Protection
7. Strengthening U.S.-South Korea-Japan Cooperation in Maritime and Economic Security
8. Defending the Energy Security Path: U.S.-South Korea-Japan Strategic Cooperation
9. Trilateral Cooperation Among the U.S., South Korea, and Japan in Countering North Korean Cyber Threats
10. How Will a Second Trump Term Shape U.S.-South Korea-Japan Trilateral Cooperation on North Korea?
11. U.S.-South Korea-Japan Trilateral Exercises as a Means of Strategic Communication
12. Command and Control in U.S.-South Korea-Japan Relations: Cooperation and Sovereignty
13. Conventional-Nuclear Force Coordination: The Way Forward for U.S.-South Korea-Japan Trilateral Security Cooperation
14. Trilateral Cooperation Among the U.S., South Korea, and Japan on Non-Combatant Evacuation Operations

Document Introduction

This report is compiled from the featured roundtable in the January 2025 issue of "Asia Policy," gathering in-depth analyses from fifteen leading scholars from South Korea, Japan, and the United States. The core research context is the commencement of Trump's second term in January 2025, the inauguration of Japan's Shigeru Ishiba cabinet, and the domestic political uncertainty triggered by the impeachment of South Korean President Yoon Suk-yeol. The report aims to systematically assess the sustainability of U.S.-South Korea-Japan trilateral cooperation in the face of leadership changes, historical legacies, domestic political polarization, and increasingly severe regional security challenges, providing multidimensional policy recommendations for deepening and institutionalizing cooperation.

The report first traces the origins and evolution of trilateral cooperation from a historical perspective, noting that it began in the 1990s to address North Korea's nuclear issue but has long been affected by fluctuations in Japan-South Korea relations, shifts in U.S. policy, and misalignments in the strategic interests of each country. The 2023 Camp David Summit marked a historic high in cooperation, achieving substantive progress in military exercises, real-time missile warning data sharing, supply chain early warning systems, and economic security dialogues. However, these achievements heavily depend on the personal political will and strategic consensus of the three leaders—Yoon Suk-yeol, Biden, and Fumio Kishida—and its institutional foundation remains fragile.

Several scholars delve into the core structural obstacles hindering the deepening of trilateral cooperation. Political polarization within South Korea is seen as a key challenge, particularly regarding historical issues and Japan policy, with significant differences between conservative and progressive voters and elites, which could cause foreign policy to swing drastically with changes in government. Although Japan-South Korea relations have recently improved due to shared strategic interests, historical perception issues such as comfort women and forced labor are far from resolved, as evidenced by the 2024 disagreement over the Sado Mine memorial activities. Public surveys show that while majorities in both countries support bilateral and trilateral security cooperation, South Koreans primarily focus on the North Korean threat, whereas the Japanese public is more concerned about countering China, reflecting differences in cooperative motivations.

The report provides a thematic analysis of opportunities and risks for trilateral cooperation in various specific fields against the backdrop of a potential return of Trump's "America First" policy. In the realm of economic security, the policy toolkits of the three countries (e.g., investment screening, industrial subsidies) have differing combinations of objectives, with the U.S. leaning more toward protectionism, while Japan and South Korea are relatively cautious. Future cooperation needs to find a balance between enhancing supply chain resilience, boosting industrial competitiveness, and implementing protective measures. In the security domain, the report explores specific pathways such as countering North Korean cyber threats, conducting trilateral military exercises as a means of strategic communication, improving command and control coordination, and developing a concept for conventional-nuclear force coordination. Energy security cooperation (e.g., LNG, civilian nuclear energy, clean hydrogen) and maritime transportation security are also seen as promising areas for collaboration to reduce dependence on China and Russia.

Finally, the report emphasizes the urgency of institutionalization. The establishment of the Trilateral Coordination Secretariat in November 2024 is an important step, but further institutionalization of high-level coordination channels such as regular summit meetings is needed. Scholars recommend strengthening inter-parliamentary exchanges among the three countries, leveraging the bridging role of experts and opinion leaders, and expanding societal consensus between Japan and South Korea within the framework of universal values like human rights, thereby transcending historical disputes and laying a more solid social and value foundation for trilateral cooperation. Overall, this roundtable concludes that although the path ahead is fraught with variables, maintaining and deepening U.S.-South Korea-Japan trilateral cooperation aligns with the fundamental strategic interests of all three countries in the face of North Korea's continued provocations, deepening China-Russia-North Korea coordination, and challenges to the Indo-Pacific regional order.