The Meaning of U.S. Troop Withdrawals from Korea

Q3: Will the troop withdrawals undermine the security of South Korea?

A3: The 4,500 troops in question approximate the size of the Stryker Brigade Combat Team, an expeditionary, combined mobile force designed to respond to a range of potential contingencies. The Stryker Brigade was introduced to Korea in 2022 during the Biden administration to replace the Armored Brigade Combat Team. The Stryker Brigade operates on a nine-month rotational deployment and would likely rotate off the peninsula permanently. This would leave one artillery brigade on the peninsula with existing combat units.

The impact of the removal of one brigade from Korea on peninsular security should be assessed in terms of defense and deterrence. The withdrawal of one brigade should not undermine the alliance’s defense capabilities. South Korea’s military plays the primary role in terms of conventional forces to contend with a North Korean attack in conjunction with U.S. air, naval, and intelligence and reconnaissance assets. The South Korean military is better equipped and trained than its North Korean opponents in a conventional fight. 

The impact of a troop drawdown on deterrence is less clear. While U.S. troops will still remain on the peninsula, providing the tripwire to ensure U.S. defense commitments, the trendlines clearly are moving toward a reduction, if not total removal, of the U.S. ground troop footprint as Washington’s focus shifts singularly to Beijing. This will raise questions in the minds of both South Koreans and North Koreans about the long-term credibility of the U.S. defense commitment. Indeed, the removal of all troops—the traditional “tripwire” that assures the U.S. security commitment—would raise core questions about the credibility of U.S. extended nuclear deterrence despite the Washington Declaration and Nuclear Consultative Group established by the previous U.S. administration. Moreover, the U.S. drawdown would take place in a heightened threat environment that is not conducive to allied confidence. A confluence of forces—China’s assertiveness and nuclear buildup, North Korea’s confidence, buoyed by the new relationship with Russia as a result of its arms trade with Putin for his war in Ukraine, and the unpredictable nature of President Trump—could lead adversaries like Kim Jong-un to miscalculate. 

Q4: Will there be more troop withdrawals from South Korea?

A4: We could see further changes in U.S. force structure on the peninsula that include reduced ground troops and enhanced air and naval capabilities (for a Taiwan contingency). While the pace of these changes will follow a military rationale, it could be accelerated by President Trump, who has made no secret of his desire to remove ground troops from Korea. CSIS data-scraping of Trump’s statements about this topic dates back over 35 years, long before he entered politics. Trump has consistently maintained the position that South Korea is a “rich country” that is “cheating” the United States on trade (because of the bilateral trade surpluses in South Korea’s direction), and that Seoul should be managing its own defense rather than “free-riding” off the U.S. security commitment. This belief has translated into policies by Trump calling for exponentially large increases in South Korean annual payments for the non-personnel costs of stationing U.S. troops in Korea (Special Measures Agreement), as well as the bevy of tariffs, including the 25 percent reciprocal tariff levied against South Korea. 

Q5: What are the implications of troop withdrawals for the new South Korean government?

A5: While the United States will have informed South Korea that the withdrawal of the brigade is under study, the absence of a fully functioning, non-interim government for the past six months certainly disadvantaged Seoul in terms of being able to shape the conversation in Washington. The new government will immediately face some difficult decisions. On the one hand, resisting strategic flexibility (i.e., the concept that U.S. forces in Korea will be used for off-peninsula contingencies) will likely be interpreted by U.S. military planners not only as out of step with the administration’s policies, but also seen by Trump as “free-riding” by the Korean ally, which might cause him to take vindictive actions to express his displeasure. This could even include pulling all troops out of South Korea. 

On the other hand, embracing strategic flexibility may appeal to Washington, but will be perceived negatively by Beijing as South Korea’s joining the U.S. side in a Taiwan contingency. For the progressive base in South Korea and in the Democratic Party of Korea, such a decision would also be seen as controversial and detrimental to the core objective of inter-Korean reconciliation by tightening the U.S.-Korea-Japan configuration against China and North Korea. These impending military and strategic decisions for the new government only exacerbate a policy environment complicated by the reciprocal tariffs, auto tariffs, auto parts tariffs, and steel and aluminum tariffs.

Q6: What should the policy be going forward?

A6: The Trump administration needs to stay in close coordination with its allies as it enacts changes to the military footprint in the Indo-Pacific. Withdrawing troops from one longstanding location, though it may make sense to the Pentagon, does not happen in a policy vacuum and could lead to unintended consequences detrimental to U.S. interests. Drawdowns need to be coordinated at the operational level with adjustments that enhance the South Korean military’s capabilities to bear a greater share of the defense burden. Close consultations also need to be had with Japan, which sees any reduction of defense and deterrence capabilities on the Korean peninsula as directly undermining Japan’s security.

Barreling ahead with a U.S. plan for reorienting force posture without such consultations creates unneeded alliance friction. For example, if Seoul believes the United States is operating without any regard for allies, then it might also take a self-help view for its defense. Japan, at least currently, has at best tempered confidence that South Korea can maintain the burden of defense and deterrence on its own, and may take its own actions to secure itself.

The Trump administration also needs to precede any further troop reductions with a comprehensive intelligence assessment of whether Kim is emboldened or deterred by U.S. moves. Trump has shown a tendency to forge ahead with policies on the Korean peninsula (e.g., the so-called “bloody nose” strike, summit diplomacy, and cancellation of military exercises) without the necessary due diligence in terms of consultations within the interagency process, with allies, and intelligence assessments vis-à-vis the adversary. If such force posture adjustments lead to opportunistic aggression or strategic miscalculation by North Korea or other actors, then the goal of being laser-focused on preparing for a Taiwan fight will be undermined. 

Victor Cha is president of the Geopolitics and Foreign Policy Department and Korea Chair at the Center for Strategic and International Studies in Washington, D.C.