01 Sep US Scales Back Joint Military Exercises with South Korea

Key Judgements

The United States’ decision to substantially reduce its annual Ulchi Freedom Shield (UFS) exercise with South Korea, followed by the cancellation of a separate major amphibious exercise, has increased uncertainty surrounding the reliability and future direction of the US-South Korea security alliance. UFS was reduced from eleven to five days following an order from US President Donald Trump, who cited the financial cost of the exercises, his relationship with North Korean leader Kim Jong Un, and South Korea’s refusal to participate in the US-led conflict with Iran. The subsequent cancellation of September’s Ssangyong amphibious exercise, attributed to US logistical constraints resulting from the Iran conflict, has further reinforced concerns that competing US military commitments could reduce Washington’s ability or willingness to maintain its previous level of engagement in East Asia.

Although the developments do not indicate an imminent weakening of the US commitment to defend South Korea, they are likely to intensify debate within Seoul over greater military self-reliance and raise concerns regarding the predictability of US security guarantees. For organisations operating in South Korea, the immediate security environment remains stable. However, increased uncertainty surrounding the alliance, combined with continued North Korean missile activity, creates a greater requirement for organisations to maintain contingency arrangements and prepare for region-wide reductions in US force posture in Asia-Pacific.

Objectives

This analysis examines the US decision to reduce joint military exercises with South Korea and assesses its implications for the US-South Korea alliance and security environment on the Korean Peninsula. The assessment considers the potential impact on deterrence, South Korean defence policy and organisations operating in South Korea.

Context

Ulchi Freedom Shield is one of two major annual US-South Korean military exercises intended to strengthen interoperability and preparedness for a potential conflict with North Korea. The 2026 exercise began on the 17th August and was originally scheduled to continue until the 27th August. However, President Donald Trump ordered the Pentagon to “substantially reduce” the exercise shortly before it began, arguing that the drills were costly and sent an unnecessarily hostile signal towards North Korea. Trump also linked the decision to Seoul’s refusal to participate in US military operations against Iran.

Following the directive, the exercise concluded on the 21st August, six days earlier than planned. The second phase was effectively cancelled, whilst several associated live-training activities were reduced or cancelled. Despite this, South Korea and the US intend to conduct approximately 159 combined field-training exercises during 2026, meaning the reduction does not constitute a broader suspension of bilateral military cooperation.

The reduction was followed on the 24th August by confirmation that the US had cancelled the upcoming Ssangyong exercise, a major division-level amphibious drill involving US and South Korean forces. The US Marine Corps had reportedly informed its South Korean counterpart in June that it would be unable to participate because of force-availability constraints resulting from US military involvement in Iran. The two countries remain in discussions over potentially resuming the exercise.

The developments occur amid continued tensions with North Korea. Pyongyang has consistently described US-South Korean exercises as preparations for invasion and has rejected the reduction of UFS as insufficient to alter what it considers hostile US policy. North Korea also continued ballistic missile activity during August, demonstrating that the reduction has not immediately resulted in a corresponding reduction in military activity by Pyongyang.

Analysis

The reduction of UFS and cancellation of Ssangyong are unlikely to significantly undermine South Korea’s defensive capabilities in the short term. Around 28,500 US personnel remain stationed in South Korea, whilst the countries retain extensive integration capabilities. Nevertheless, repeated reductions in large-scale exercises could gradually affect interoperability and preparedness if they become sustained rather than temporary. More significantly, the decisions have created uncertainty over the predictability of US policy towards South Korea, particularly as the UFS reduction was announced with limited prior consultation with Seoul.

The developments are likely to accelerate existing efforts by Seoul to strengthen its independent defence capabilities. More broadly, the cancellation of Ssangyong demonstrates how US military commitments outside Asia can affect force availability in the Indo-Pacific. This is particularly evident in light of the US redeploying aircraft carrier USS George Washington from the Pacific theatre to the Middle East in August. Should the Iran conflict continue to absorb US assets, Washington is likely to face increased pressure to maintain simultaneous commitments across the Middle East and Indo-Pacific, as well as Europe. This does not indicate an imminent US withdrawal from South Korea, but it increases uncertainty regarding the resources available to reinforce regional allies during periods of concurrent crises.

For organisations operating in South Korea, the immediate impact is likely to remain limited. There is currently no indication that the reduction in exercises materially increases the likelihood of armed conflict, and normal business operations in Seoul and other major commercial centres are unlikely to be affected. However, the increasingly unpredictable nature of US-South Korean security relations are likely to increase the potential for short periods of heightened geopolitical tension, particularly following North Korean missile launches and exercises, or sudden changes in US policy. Organisations are advised to maintain and regularly review crisis-management, and business continuity procedures, particularly given the limited warning that could accompany a serious deterioration in inter-Korean relations. 

Overall, the August reductions do not represent a fundamental deterioration in South Korea’s security environment. However, they demonstrate increasing uncertainty surrounding the future structure of the US-South Korea alliance and Washington’s ability to balance competing global military commitments. Further, reductions in exercises or US deployments is likely to increase pressure on Seoul to assume greater responsibility for its own defence and could contribute to greater regional uncertainty. For organisations operating in the region, the primary concern is therefore not an immediate increase in physical security risk, but the possibility that a less predictable regional security environment reduces warning time and increases the importance of maintaining effective contingency planning.