Trump Uncertainty Pushes Japan and South Korea Into Closer Strategic Embrace

Japan and South Korea are moving toward their closest strategic alignment in years, driven less by mutual affection than by shared unease over the United States under President Donald Trump, according to an analysis published by the East Asia Forum.

The warming, first energised by the August 2023 trilateral summit at Camp David under former South Korean president Yoon Suk-yeol, has survived leadership changes in all three countries. Even the awkward pairing of Japan's conservative nationalist Prime Minister Sanae Takaichi with South Korea's progressive President Lee Jae-myung has failed to slow the momentum. Their meeting in Lee's hometown of Andong on 18-19 May 2026 was described as warm, surprising critics who feared Lee's past criticism of Japanese colonial rule would derail progress.

The analysis, written by Stanford lecturer and Korea Economic Institute fellow Daniel Sneider, attributes the shift to a common need to hedge against both China and an erratic Washington. Trump's trade wars and military interventions have sent shocks through both economies, and one senior South Korean official was quoted saying the two governments share "anxieties about Washington" rather than concerns centred on Beijing.

Officials in Seoul are reportedly weighing steps once considered unthinkable, including a possible non-aggression pact that would set aside territorial disputes and even movement toward a mutual defence treaty. While such measures would test public tolerance in both countries, their mere discussion signals how deeply Trump-driven uncertainty is reshaping the region. Notably, the deepening is occurring without active involvement from the White House, which has shown no interest in the trilateral framework built under former president Joe Biden.

Yet rhetoric has outpaced concrete action. South Korea has expressed interest in joining the Comprehensive and Progressive Agreement for Trans-Pacific Partnership but has not formally applied, constrained partly by lingering restrictions on Japanese seafood tied to the Fukushima accident. In defence, Japanese Defence Minister Koizumi Shinjiro visited Seoul in June 2026 but could not secure a long-sought military logistics pact, with Lee citing public sentiment over historical grievances as the obstacle.

Deeper divisions also loom. Lee has worked to preserve ties with Beijing and appears willing to back a potential Trump summit with North Korean leader Kim Jong-un that could tacitly accept Pyongyang's nuclear status—an outcome Tokyo fears. Unresolved wartime compensation cases against Japanese firms continue winding through South Korean courts, and a single visit by Takaichi to the Yasukuni Shrine could reignite tensions.

For now, Sneider concludes, the path to improved ties remains open, thanks largely to Trump and, to a lesser degree, Chinese President Xi Jinping. How long that window stays open, however, is far from certain.