The period from the inauguration of Yoon Suk-yeol in May 2022 to the astonishing events of this month saw a remarkable improvement in relations between Japan and South Korea. This was in contrast to the breakdown in ties between the two nations under former South Korean President Moon Jae-in and then Japanese Prime Minister Abe Shinzo, when their respective administrations failed to manage the relationship.
Under Moon’s administration, the South Korean judicial system ordered defendant Japanese companies to pay damages to former civilian workers from the Korean Peninsula. In response, Yoon’s government offered a resolution in which a foundation under the South Korean government would make the payments on behalf of the companies. This was aimed at reconciling the judicial decision with the 1965 Agreement on the Settlement of Problems concerning Property and Claims and on Economic Co-operation between Japan and the Republic of Korea. Abe’s successor as prime minister, Kishida Fumio welcomed this proposal, leading to an unprecedented 12 summits between the leaders of the two nations. However, in South Korea, the decision attracted strong criticism, with a majority of the public dissatisfied with Yoon’s attempt to resolve the issue. Moreover, subsequent rulings following the Supreme Court’s precedent have been handed down, with the consequence that the issue still persists.
Given the domestic criticism, why did the Yoon administration make such a decision in the first place? We should view the decision in the context of a major shift in the overall plan for South Korean diplomacy. First, there was a change in policy towards North Korea. In contrast to the Moon administration, with its focus on engagement, the Yoon administration employed policies that focused on deterrence. These policies respond to an increase in the reliability of U.S. extended nuclear deterrence in response to North Korea’s nuclear missile development. Second, there was a shift in South Korea’s position on U.S.-China tensions. The Moon administration adhered to a policy of “strategic ambiguity,” refusing to take sides. However, the Yoon administration chose to join the “Indo-Pacific Strategy,” a strategy promoted by Japan and the U.S. in response to China. Third, there was a shift towards strengthening the US-Korea Alliance. While the Moon administration bolstered its alliance to gain support and cooperation from the U.S. with its engagement policies with North Korea, the Yoon administration oriented itself toward a strengthened partnership in the global sphere, with the goal of improving the reliability of extended nuclear deterrence. Consequently, while Moon’s diplomacy indicated a “Korean Peninsula-centric” stance, Yoon’s diplomacy was focused on a “Global Pivotal State.”
Building on Yoon’s diplomacy will require strengthening security cooperation with Japan and the U.S., which already share diplomatic goals. This would dissolve the distrust between Japan and South Korea, which had hindered cooperation in the past. As a start, joint security cooperation between Japan, the U.S., and South Korea led to the “Camp David Principles, The Spirit of Camp David” in August 2023, as well as the establishment of the “Japan-U.S.-ROK Trilateral Coordinating Secretariat” in November 2024 to further enhance the framework for joint security cooperation between the three nations.
In Japan, the Kishida administration has now given way to the government of Ishiba Shigeru. With Ishiba holding the most liberal position among key policymakers in the ruling Liberal Democratic Party (LDP) when it comes to issues of historical awareness that have caused tension between Japan and South Korea, Seoul no longer needed to worry about what the new Japanese prime minister might say or do. That in turn would normally be expected to help keep relations between the two countries on a favorable footing.
That is, at least until this month. After he took the astonishing step of briefly declaring martial law on December 3, Yoon was impeached on December 14 by the National Assembly. He has been forced to step aside while he is investigated on charges of insurrection. Prime Minister Han Duck-soo became acting president and will provide basic oversight of the country’s affairs.
If the Constitutional Court hands down a ruling that relieves Yoon from his duties, a political vacuum of at least three to four months is likely until a new president can be elected. Summit diplomacy will effectively come to a halt. If a change of government occurs and the opposition takes power, longstanding criticism of the Yoon administration’s Japan policy could lead to a reassessment of diplomacy with Japan, potentially complicating the bilateral relationship once again. At the very least, the events of the past two weeks highlight the fragility of Japan-South Korea relations, which had been highly reliant on the Yoon administration.
Japan and South Korea will celebrate 60 years of normalized relations in 2025, but given the current situation, they will have difficulty in making bold, mutual compromises to change the status quo. The best that can be expected for now is a maintenance of the status quo. The Sado Gold Mine was designated as a World Heritage Site with cooperation from the Yoon administration. A memorial service for victims was originally planned to be held in November, with official representatives from both countries participating. However, due to conflicting information, each country ended up having its own service, underscoring just how thorny historical issues remain between Japan and South Korea.
In the midst of these issues, the world awaits the inauguration of the second administration of Donald Trump. What is most interesting is that during Trump’s previous time in power, it was widely felt in Japan that the relationship between the U.S. and Japan was good, while U.S.-South Korean relations were rocky. However, in South Korea, and in particular the Moon administration, the opposite conclusion was drawn: South Korean ties with Washington were good, while it was U.S.-Japan relations that were troubled.
Unlike the Biden administration, which was instrumental in establishing joint security cooperation between the U.S., Japan, and South Korea as a mediator between the two East Asian neighbors, Trump appears to think that competition between Japan and South Korea over loyalty to the U.S. is to the latter’s benefit. A period of competition over U.S. loyalty between Japan and South Korea may indeed be what lies ahead. That makes it even more important for Japan to secure a line of communication with the Trump administration by further solidifying cooperation with South Korea. To do that, it is essential for Tokyo to take the initiative in reaching out to the next South Korean administration, looking to build on the results the two countries have already achieved in that regard.
KIMIYA Tadashi is a professor at the University of Tokyo.