U.S. Congress Sets Floor on Troop Levels in South Korea, Reaffirms Commitment to Alliance

The passage of the National Defense Authorization Act (NDAA) for the next fiscal year by the U.S. Congress on Dec. 17, which includes provisions limiting any reduction in U.S. Forces Korea (USFK), is widely seen as an effort to underscore Washington’s view of South Korea as a top-tier ally.

Once formally enacted with President Donald Trump’s signature, the NDAA will prohibit the U.S. government from using congressionally approved defense funds to reduce the number of U.S. troops stationed in South Korea below the current level of approximately 28,500. The legislation also bars the use of funds to complete the transfer of wartime operational control (OPCON) in any manner that deviates from plans jointly agreed upon by Washington and Seoul.

While the law includes a waiver provision allowing the restrictions to be lifted after 60 days, this is contingent on the administration reporting to the relevant congressional committees that such changes would serve U.S. national security interests and that sufficient consultations have been conducted with South Korea, Japan, and other allies contributing militarily to the United Nations Command. Observers note that the breadth of these reporting requirements is expected to function as a significant safeguard against abrupt policy shifts.

The debate over USFK troop levels is closely tied to the Trump administration’s broader security doctrine of “strategic flexibility,” which emphasizes the ability to redeploy U.S. forces worldwide—including those stationed in South Korea—as mobile strike assets rather than having them fixed to specific regions. Reflecting this view, the U.S. administration previously issued a statement opposing the provision ahead of the NDAA’s passage in the Senate, arguing that it unduly constrains the president’s authority as commander in chief.

Adam Kozlowski, a senior fellow at the Atlantic Council, said the Senate’s approval of the bill reflects “strong, or at least justified, concern that the Trump administration could pursue excessive reductions in U.S. troop levels in South Korea.” He added that the measure is intended to reaffirm Washington’s commitment to the U.S.–South Korea alliance.

At the same time, the Atlantic Council noted that critics argue the provision could undermine the ability of USFK and U.S. Indo-Pacific Command to adjust force posture flexibly in response to a rapidly evolving security environment. According to this view, the restrictions impede a “conditions-based” approach that allows troop levels and modernization decisions to be adjusted as circumstances change. Kozlowski echoed this concern, warning that “reassurance based solely on troop numbers can come at the expense of regional readiness and operational effectiveness.”

For similar reasons, the NDAA also prevents U.S. troop levels in Europe from being reduced below 76,000. As with South Korea, however, exceptions are permitted if the Department of Defense consults in advance with NATO allies and demonstrates to Congress that any such reductions would not pose a threat to U.S. national security.