US Vice President JD Vance gave a speech that shocked European allies at the Munich Security Conference this month, putting US commitment to European security into question. But on the sidelines of the event, US Secretary of State Marco Rubio was meeting with the Japanese and South Korean foreign ministers.
It was the first high-level meeting of the Japan–South Korea–US trilateral since Donald Trump became president. Although the three sides reaffirmed their ‘unshakable’ partnership in their joint statement, the new Trump administration’s approach throws doubt on this other important US partnership.
The Japan–South Korea–US trilateral matters for strategic reasons. It allows the US and its Indo-Pacific partners to discuss regional challenges, jointly develop responses to provocations and signal cohesion.
There is scope to build stronger deterrence capabilities and enhance collective defence integration against rising threats from China, North Korea and Russia. Developing such minilateral cooperation requires quiet, painstaking and consistent diplomacy.
Yet Trump’s diplomacy and outlook consider such alliances as sources of potential short-term gain, not long-term strategic value. And his administration lacks the diplomatic heft and political will to continue the engagement that has so far benefited the Japan–South Korea–US trilateral.
Trilateral cooperation under Biden
The trilateral relationship was integral to the Biden administration’s efforts to bolster the US presence in the Indo-Pacific. Through a ‘latticework’ of coalitions, the administration sought to reinforce existing bilateral partnerships with minilateral groupings to build collective capacity in security and non-security domains in the Indo-Pacific.
Three goals motivated Washington to strengthen the Japan–South Korea–US trilateral. The first was to integrate two of its closest regional allies, which had struggled to cooperate on security issues due to long-standing animosities and varying strategic priorities. The second was to signal that ‘America is back’ to work with allies after the unilateral ‘America First’ agenda of Trump’s first term. The third was to push South Korea to adopt a greater international role, since historically its focus was on the existential threat from North Korea.
Strong bilateral ties between Seoul and Tokyo are central to the trilateral. Previously, tensions between the two were the biggest obstacle to the partnership. Things began to shift in 2022 when Yoon Suk Yeol became president of South Korea. For him, strengthening the alliance with the US and normalizing ties with Japan were key to his country’s future strategic posture. The subsequent willingness to reciprocate by Japan’s then prime minister, Fumio Kishida, meant that conditions were ripe for a renewed US push for trilateral cooperation.
A ‘new era’ of trilateral cooperation was inaugurated at the Camp David Summit in August 2023. Since then, the trilateral mechanism has enhanced the normalization of Japan–South Korea ties, enabled Seoul to play a fuller role in the region, and led to greater strategic alignment on North Korea and China policies across the three partners.
In just two years, security and defence officials from the three sides met at least 80 times across all levels of government, and the three countries held their first multi -domain military exercise. Even more dialogues were held to strengthen economic, financial, technological and people-to-people cooperation.
Hurdles to trilateral cooperation under Trump
Trump’s return to the White House imperils the trilateral on two accounts.
First, unlike Biden, Trump views alliances as dependencies to be exploited by extracting maximum benefits to suit his America First agenda. Trilateral cooperation will struggle to muddle through the volatility and incongruency of bilateral demands coming from the Trump presidency towards not just one, but two, allies.
Disagreements over cost-sharing of US forces in Japan and South Korea, their balance-of-trade with the US, Trump’s plans for reciprocal tariffs, and military expenditure could all affect the trilateral mechanism.
How Trump handles North Korea, China and Russia could also undermine trilateral cooperation. Strategic misalignment was already emerging at Munich.
The Japanese and South Korean foreign ministers spoke jointly about the connectivity of the Euro-Atlantic and Indo-Pacific security theatres, noting that the nature of a peace settlement in Ukraine will directly affect East Asian security. Trump’s team, meanwhile, could not have gone farther to stress how it considers the two theatres as unambiguously separate.
Trump’s penchant for dealing directly with autocratic leaders to showcase his ability to extract the best deals will also whittle the trilateral’s primary goals and mode of functioning, notably the ‘Commitment to Consult’ agreed at Camp David.
Second, US willingness to mediate between Japan and South Korea has previously created space amid the two nations’ historic animosities and contentious political issues.
With the US in the room, the Japan–South Korea relationship can be framed on more strategic grounds where they can converge. Polling also suggests strong domestic support in both countries for security cooperation with a US presence to stabilize the Korean peninsula and contain China’s rise.
