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Bottom line up front: Language in the Senate NDAA prohibiting force posture changes on the Korean Peninsula should be amended: Instead of an archaic number of US service members, Congress should opt for a requirements-based model that allows the United States to tailor the force to the operational and strategic situation of the Korean Peninsula and the broader Indo-Pacific. 

During negotiations on the final NDAA text, Congress should instead define what a force in Korea needs to do, considering theater-level nuclear systems, noncombatant evacuation, logistics and medical support, conventional strike and targeting capabilities, integrated air and missile defense, and base protection.

Background: Current force posture language 

The future of US force posture on the Korean Peninsula has taken a spotlight role in this year’s negotiations surrounding the must-pass National Defense Authorization Act (NDAA), legislation shepherded through the Congress by the House and Senate armed services committees. This year, the committees appear to have forgone the formal “conference” process, reverting to negotiating the final NDAA text behind closed doors in an “informal conference.” This process, increasingly common in recent years, provides an outsized influence to the chair and ranking member of the committees in the House and Senate, whose teams manage negotiations. The Senate Armed Services Committee has restored and enhanced language prohibiting the use of funds to reduce the number of US service members serving on active duty in the Republic of Korea (ROK). In fact, this year’s Senate NDAA language far surpasses the scope and requirements of past language. In the John S. McCain FY 2019 NDAA, Section 1264 set the floor at 22,000 active duty personnel. Section 1264 required only simple certifications that a proposed future reduction was in the national security interest of the United States and that the secretary “has appropriately consulted” with allies, including Japan and the Republic of Korea. 

In contrast, this year’s Senate NDAA restricts any reduction below 28,500 US military personnel “permanently stationed in or deployed to” South Korea. It further requires not just certifications that a proposed reduction of force is in the national security interest of the United States and that the “appropriate consultations” have occurred but also assessments by the secretary of defense, in consultation with the commander of US Forces Korea (USFK), the commander of US Indo-Pacific Command (INDOPACOM), the secretary of state, and the director of national intelligence. These assessments would include a laundry list of reports on the impact and cost of reducing forces on the defense posture of affected nations and INDOPACOM, plus the ability to execute contingency plans, carry out joint training, and sustain the credibility of US deterrence commitments. The Senate NDAA also requires a detailed description of each consultation with allies instead of the previously required  simple certification that consultations have occurred, and a new independent risk assessment by the commanders of USFK, INDOPACOM, and the chairman of the Joint Chiefs of Staff on the impact of any proposed reductions. Finally, the Senate version of this prohibition envisions a ninety-day shot clock starting when the certification is transmitted to Congress, which must be unclassified, before the administration could act on either a transfer of command or reduction below 28,500 active-duty personnel. This ensures Congress retains the initiative to introduce further legislation to prevent a reduction. 

A remodeled Korean alliance for an age of great power competition

Taken as a whole, the language is a strong signal from the Senate Armed Services Committee that Congress will not accept a smaller US force posture on the peninsula, and institutes severe safeguards to ensure compliance. With discussion of cuts to USFK being raised regularly—a reporter asked about the possibility during the August 25 US-South Korea meeting in the Oval Office—Congress is understandably concerned that a severe reduction in USFK personnel may be in the offing, which could reduce the confidence the United States’ South Korean and other Indo-Pacific allies have in Washington’s commitment to their defense.

However, as one of us pointed out in a recent analysis, the 28,500 troop floor is a “longtime artificial constraint” based on legacy commitments divorced from strategic analysis—the number is just a political signal of commitment to South Korea, not tied to a specific level of military capability. The US military posture in Korea has more strategic and operational relevance than just reassuring South Koreans, and there is a lot more to measuring the capability of that posture than taking a headcount. 

Given that the Pentagon in 2022 identified China as the United States’ “pacing challenge,” discussions of cuts to USFK are often tied to a reorientation toward countering China in the Indo-Pacific. The reporter’s question to Trump was characteristic: “Would you consider reducing the number of US forces in South Korea so that the United States can have more flexibility in the region?” Some advocates for major cuts in USFK pointedly portray the current level of US forces in Korea as a liability when it comes to facing China. Two of these advocates noted in a July analysis: “Seoul has not offered the United States unrestricted contingency access to use its bases for operations elsewhere in the theater during a conflict.” This is a strawman argument, as this level of “unrestricted contingency access” is a high bar indeed to expect from another sovereign state. No regional US ally offers the United States such access. Even the Pacific Islands states who have largely ceded their military responsibilities to the United States under their Compacts of Free Association have placed some restrictions on certain types of munitions that the military can host on their territory. Is it realistic to expect that US forces stationed in any sovereign US ally would have a blank check to attack Beijing without prior consultation and thereby drag the ally into a war with China? Other US allies have rightfully pointed out that the choice of entering future hostilities will ultimately be down to the “government of the day.” This lack of clarity creates inherent risk for US planners who are forced to design contingencies with questionable allied involvement and support.

The overall questions about how USFK fit into the larger strategic picture vis a vis China, and the potential constraints on employing USFK in a US-China confrontation are valid ones, however. Seoul is also understandably not eager to antagonize Beijing by providing clarity—particularly not publicly—on how it would see its alliance obligations and an acceptable role for USFK in the event of a hypothetical US-China war. This lack of clarity and Seoul’s unwillingness to offer a blank check for USFK operations against China notwithstanding, Korea is very unlikely to remain neutral in such a conflict or to try to shut down various forms of USFK support to US military operations elsewhere. Given Korea’s strategic location, its well-developed  infrastructure, and the network of US and ROK bases and military support functions there, USFK and the ROK could provide valuable aid to US operations and foster dilemmas for Beijing during a hypothetical US-China war—even without engaging in direct combat, as South Korean experts have increasingly noted. Further, there is every reason to expect that if US territory or US bases in Korea are attacked by China in the ensuing conflict, South Korea would fight alongside the United States, bringing additional capability and basing options, while USFK units and bases could be fully unleashed to play key direct combat roles. 

To address the US concerns raised by the current state of ambiguity, a simple and general reassurance from Seoul would be a good start, as we have previously argued: “The South Korean president should at least tacitly affirm that Seoul will adhere to the 1953 mutual defense treaty as a two-way treaty, not just a commitment by the United States to defend South Korea against North Korea.” Such a reassurance could help set the stage for a recalibration of US Forces Korea to both meet US obligations under the 1953 mutual defense treaty and to better support broader US defense priorities vis-a-vis China. 

A strategically advantageous compromise

Refining a force posture based on operational requirements rather than political symbolism is common sense. Congress should clearly define essential tasks in furtherance of the national interest as the floor for force reduction, instead of an archaic number detached from operational needs. Spelling out specific requirements for the force posture on the Korean Peninsula would not only help dispel misconceptions about the usefulness of such forces but also enable future force posture recalibration to build on a strategically coherent foundation. Congress should consider a floor built around the following key operational and strategic needs and ensure that the commanders of INDOPACOM and USFK can provide independent assessments on the force posture requirements to meet these needs.

• Ensuring nuclear deterrence through theater-level nuclear capable systems. F-35A fighters have already been deployed in recent joint exercises. A long-term deployment or permanent stationing of dual-capable F-35As in Korea, able to carry nuclear or nonnuclear weapons and explicitly trained and prepared for nuclear missions, would send a strong message of deterrence. This ultimately could be far more important to reassuring South Koreans of US commitment to extended deterrence than any particular number of US military personnel stationed on the peninsula. 
• Improving the ability to conduct rapid conventional strikes against targets throughout North Korea and other adversaries within conventional range, such as China. 
• Supporting an integrated air and missile defense architecture across the Republic of Korea to provide assurance to the Korean people, protect the tens of thousands of American citizens living in Korea, and protect US service members and assets.
• Maintaining a network of distributed and hardened bases and facilities to mitigate the risk of saturation attacks on core facilities severely degrading the US capability to respond. 
• Ensuring the physical safety and protection of US service members, bases, and military assets deployed to the Korean Peninsula. 
• Preparing noncombatant evacuation operations for Americans in South Korea, and other key allied personnel in the event of war.
• Retaining sufficient medical, logistical, and maintenance support in Korea to support deployed forces in a high-intensity conflict environment.
• Engaging in intelligence collection, analysis, and targeting against North Korea and other regional adversaries.

Compromise language focused on these types of requirements may get a better reception from the Trump administration. It is also likely to fare better in the House of Representatives, whose draft NDAA language currently only includes a nonbinding “Sense of Congress” provision on force reductions on the Korean Peninsula. Such requirement-based amendments to the Senate language can thus simultaneously assure observers of the strength of the US-South Korea alliance while ensuring that the US force posture is lean and reflective of the national interest.

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Markus Garlauskas was the National Intelligence Officer for North Korea on the US National Intelligence Council from July 2014 to June 2020. He served for nearly twelve years overseas at the headquarters of United Nations Command, Combined Forces Command, and US Forces Korea in Seoul, including as chief strategist to three successive commanders of US Forces Korea.

Adam Kozloski was an aide and foreign policy adviser to US senators on the Armed Services Committee and Foreign Relations Committee until 2024.

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