By Dasl Yoon
SEOUL -- Just weeks ago, the U.S. had stationed in South Korea a full inventory of an American missile-defense system able to guard against a North Korean strike.
But after the U.S. war on Iran began, it shifted dozens of missile interceptors and other assets from South Korea to the Middle East to bolster American combat capabilities there, according to people familiar with the matter and satellite imagery.
The security relationship that allies, particularly in Asia, have with the U.S. is evolving into an era where they may be called to do more with less. And South Korea -- which the Trump administration has called a "model ally" -- is particularly feeling the pains from this transition.
"We're entering a new season of the U.S.-South Korea alliance that requires flexibility," said Ahn Byung-suk, a former deputy commander at the joint U.S.-Korea warfighting headquarters and a retired four-star South Korean general.
Some of that shift is pushed by South Korea, too. For annual spring exercises that ended Thursday, the number of field drills carried out by the U.S. and South Korea fell by more than half from the prior year. Seoul, under the left-leaning President Lee Jae Myung administration, has sought a more conciliatory approach to Pyongyang, which views the combined drills as dress rehearsals for an invasion.
In August, Gen. Xavier Brunson, the top American military official in South Korea, said to allow the U.S. to counter other unspecified threats, the South should be stronger against the North. Then, in January, the Pentagon's latest national defense strategy assessed that South Korea is "capable of taking primary responsibility" to deter North Korea.
Roughly a year ago, Defense Secretary Pete Hegseth, on his first official trip to Asia, vowed to "truly prioritize" a region facing China's rising military aggression. President Trump has pursued leader-to-leader diplomacy with Chinese leader Xi Jinping, agreeing to a pause to their trade war and a future meeting in Beijing. This week, the U.S. intelligence community toned down its view of the risk of a Chinese invasion of Taiwan by next year.
Now with the war with Iran, the U.S. is shifting military assets from the Pacific that had been available to deter China and North Korea. In addition to South Korea's Thaad assets, two ships from the Japan-based USS Tripoli Amphibious Ready Group and the 31st Marine Expeditionary Unit are being sent to the Middle East.
Doubts will rise among the U.S.'s allies in Asia, despite rhetorical affirmations of strong ties, said Henrietta Levin, a former National Security Council director for China during the Biden administration.
"The Trump administration has clearly deprioritized the Indo-Pacific" compared with recent U.S. presidents, including Trump's own first term, said Levin, who is now a senior fellow at the Center for Strategic and International Studies, a Washington, D.C.-based think tank.
South Korea is home to roughly 28,500 U.S. military personnel and hosts America's largest overseas military base. Under Lee, who took office last year, South Korea has vowed to increase defense spending to 3.5% of its gross domestic product by 2035, up from 2.3% last year -- a move that has drawn praise from Washington.
South Korea is already one of the world's biggest military spenders with a robust domestic base for defense production. The country ranks No. 5 in conventional military power, according to Global Firepower, a website publishing annual rankings of military strength across dozens of factors.
Nonetheless, Lee voiced his opposition last week to the withdrawal of U.S. air-defense assets, saying his government could do little to stop the move. But South Korea, which has its own air defenses, is still capable of deterring North Korea, Lee said.
At a House hearing on Tuesday, Michael Duffey, the Pentagon's top official for weapons procurement, acknowledged the redeployment of Thaad antimissile assets had occurred. Such flexibility, he said, represents a "tremendous strength of our system."
South Korea still appears to possess elements of Thaad, short for Terminal High-Altitude Area Defense. At least four of the Thaad launchers in South Korea appeared in recent satellite imagery analyzed by Jeffrey Lewis, of the Middlebury Institute of International Studies in Monterey, Calif.
The reduced U.S. air defenses in South Korea come as North Korean leader Kim Jong Un, emboldened by tighter military bonds with Russia, has openly flouted his nation's weapons capabilities. Kim and his young daughter recently oversaw the test of tactical-nuke launchers, and on Thursday the two rode the country's new battle tank.
South Korea's installation of Thaad in 2017 enraged China, which was widely believed to have orchestrated a campaign of economic retaliation against Seoul. The shift of Thaad assets to the Middle East represents a "conscious movement" toward strategy flexibility, said Derek Grossman, a former Pentagon official who worked on Indo-Pacific security issues.
"South Korea will downplay the moving of U.S. assets to maintain a good relationship with Trump," said Grossman, who is now a professor at the University of Southern California. "Meanwhile China is rejoicing."
Write to Dasl Yoon at dasl.yoon@wsj.com
(END) Dow Jones Newswires
March 20, 2026 07:27 ET (11:27 GMT)
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