Flashpoints | Security

US Unpredictability Is Giving Its Asian Allies New Reasons to Cooperate

Across the Indo-Pacific, several of the United States’ closest partners are investing more heavily in relationships with one another – and, increasingly, with Europe.

Japanese Prime Minister Takaichi Sane shakes hands with Australian Prime Minister Anthony Albanese at the annual Australia–Japan Leaders’ Meeting, Canberra, Australia, May 4, 2026.

When U.S. President Donald Trump abruptly ordered the Pentagon to substantially reduce joint military exercises with South Korea, officials in Seoul were caught off guard. The annual Ulchi Freedom Shield drills still went ahead, but were cut short on Trump’s order. The episode was a reminder that even one of Washington’s closest allies can find the assumptions of its security policy changed with little warning.

That uncertainty is why, across the Indo-Pacific, several of the United States’ closest partners are investing more heavily in relationships with one another – and, increasingly, with Europe. South Korea and Japan are expanding cooperation on supply chains, energy and advanced industries. Japan and Australia are linking economic security more closely to defense production and military operations. All three are also building more structured ties with the European Union.

Of course, these efforts are not an attempt to replace the United States. China’s growing power, North Korea’s weapons programs, Russia’s war in Ukraine, and repeated disruptions to energy and supply chains were already pushing like-minded countries closer together. But Trump’s second term has added another incentive: the need for relationships that remain useful when U.S. policy changes suddenly, including toward its own allies.

South Korea and Japan offer the most politically unlikely example. Their relationship has repeatedly been derailed by disputes over Japan’s colonial rule, wartime labor and historical memory. The rapprochement begun under former South Korean President Yoon Suk-yeol and former Japanese Prime Minister Kishida Fumio therefore looked vulnerable to political turnover.

Instead, it has continued under progressive President Lee Jae-myung and conservative Japanese Prime Minister Takaichi Sanae. In his August 15 Liberation Day address, Lee pointed to a year of shuttle diplomacy with Japan and highlighted cooperation in supply chains, energy, and advanced industries. The setting was just as important as the message: a South Korean president was emphasizing the practical value of ties with Tokyo on the day commemorating Korea’s liberation from Japanese colonial rule.

The substance has become harder to dismiss as symbolism. In March, Seoul and Tokyo signed a Supply Chain Partnership Arrangement that created mechanisms for information sharing and consultation during disruptions. Their industry ministries also established a regular policy dialogue covering trade, economic security, supply chains and mineral resources. At the Lee-Takaichi summit in May – their third in seven months – the two governments moved further into energy security, agreeing to explore emergency cooperation involving crude oil and petroleum products while strengthening supply-chain resilience. 

SK Hynix is now considering a large memory-chip manufacturing investment in Japan. The project may never materialize, but its consideration is telling given the history of rivalry and trade friction between the two countries’ semiconductor sectors.

Washington once provided much of the external pressure encouraging Seoul and Tokyo to overcome their differences. Under the Biden administration, the Camp David summit in 2023 made improved bilateral ties a central part of a U.S.-led trilateral strategy. Under Trump, the logic is becoming more complicated. The United States remains indispensable to both countries, but uncertainty over U.S. trade and alliance policy is also increasing the value of a relationship that does not depend on Washington to function. The Trump administration today isn’t playing the same mediating role as its predecessor did, and yet Japan-South Korea relations are arguably closer than ever.

Japan and Australia show the same trend in a more mature form. In May, Prime Ministers Takaichi and Anthony Albanese signed a Joint Declaration on Economic Security Cooperation, committing their countries to........

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