What to make of Washington’s plans to “modernize” the ROK-US alliance
Calls for expanding the scope of the USFK could have negative long-term repercussions for Seoul.
The “ironclad” U.S.-South Korea military alliance stands at a crossroads. As Washington pushes for alliance "modernization" to address China's growing assertiveness in the Indo-Pacific, Seoul finds itself navigating between American strategic imperatives and its own national interests. This tension, exemplified by growing calls from U.S. officials to expand the alliance’s military scope beyond deterring North Korea, highlights the complex challenges facing South Korea's new leadership.
USFK Focus: From Peninsula to the Pacific?
Seoul and Washington need to modernize their decades-long military alliance through "adaptability” to better face the evolved security landscape in the Indo-Pacific region. This was the main argument made by General Xavier Brunson, commander of the U.S. Forces Korea (USFK), on Wednesday.
Citing China's "unprecedented" encircling military drills against Taiwan in 2022, the U.S. General called for greater efforts at promoting collective security among like-minded nations, emphasizing that “security is not only about capabilities, but it's about coalitions, nations willing to come together quickly in moments of crisis.”
Brunson also praised the ongoing U.S.-ROK-Japan trilateral military drills, which kicked off earlier this week, saying “we are expanding beyond bilateral deterrence to integrated regional security."
The General's remarks follow months of speculation in Seoul about potential Trump Administration plans to reconfigure USFK's mission in response to the region's evolving geopolitical landscape. Multiple U.S. officials have already voiced support for this policy shift.
In July, South Korean officials reportedly said that Washington had formally asked South Korea to broaden the scope of the U.S.–ROK Mutual Defense Treaty to cover the wider Indo-Pacific region, calling the move part of the goal to “modernize” the U.S.-ROK alliance. The development came at around the same time when U.S. Secretary of War Pete Hegseth said the U.S.-Philippines Mutual Defense Treaty applies throughout the Pacific Ocean, including the South China Sea, leading to further concerns of similar expectations for Seoul under the U.S.-ROK treaty.
The State Department also directly confirmed with South Korea’s Chosun Ilbo plans to “rebalance” the roles of the USFK and South Korean military to better address regional threats.
The following month, a Pentagon official stated that efforts by the allies to modernize their alliance include expanding cooperation to ensure credible deterrence on the Korean Peninsula and "beyond"— further signaling Washington's interest in introducing greater flexibility in the use of its forces stationed in the ROK.
The State Department also expanded on this idea of modernizing the alliance, calling for an "increase in ROK defense burden-sharing," emphasizing the need for the alliance to adapt "amid an evolving regional security environment."
In addition to his comments made this week, USFK General Brunson also reaffirmed the need for modernizing the alliance last month, stating that “there needs to be changes within USFK.” He specifically cited the growing threat posed by Russia in the region as well as “the Chinese and the threat that they pose to a free and open Indo-Pacific.”
Other U.S. experts have also doubled down on the need to “modernize” the U.S.-ROK alliance, arguing that “the alliance cannot be defined solely by North Korea.” The idea to establish a “Pacific Defense Pact” has also been floated around earlier this year. According to this concept, as a potential member, South Korea could “support a broader regional orientation for its own military” and that of the U.S. forces stationed on its territory.
While much of the focus is currently on what Trump will do next, efforts to redirect American resources in the region toward addressing China's military buildup began well before Trump's return to office. Despite fundamental disagreements on many policy fronts, both former President Biden and Trump agree on the need to strengthen America's response to Beijing's growing influence.
To this end, Biden’s Indo-Pacific Strategy directly called for the U.S. “to modernize our treaty alliances” with partners in the region, including the ROK, while stressing the need to “work in flexible groupings that pool our collective strength to face up to the defining issues of our time.”
The main way Biden pushed this strategy forward with regards to the Korean Peninsula was by encouraging and facilitating greater cooperation between Tokyo and Seoul. The deepening of the trilateral partnership between the U.S., ROK, and Japan featured particularly prominently in the Biden administration’s Indo-Pacific Strategy and three-way cooperation did successfully reach new heights under Biden and former South Korean President Yoon Suk-yeol.
Seoul's Strategic Dilemma: ‘Collective’ Security vs. National Interest
While trilateral U.S.-ROK-Japan military drills are taking place this week, it remains to be seen how far the new ROK leader, Lee Jae-myung, is willing to go to continue fostering greater trilateral military cooperation involving Japan. During his election campaign, Lee explicitly said he would not be adopting the Yoon government’s Indo-Pacific strategy—which sought to expand the scope of South Korea’s defense activities throughout the region— vowing instead to return to the New Southern Policy and New Northern Policy of the former Moon Jae-in administration.
Still, as is the case for every South Korean president, Lee finds himself in a difficult position. While Washington remains Seoul’s most crucial military ally, South Korea’s national security interests don’t necessarily align with those of the U.S. when it comes to Indo-Pacific policy.
Seoul recognizes its strong economic ties with Beijing and cannot afford to align unconditionally with Washington on regional political and security matters. While America's primary concern centers on a potential Chinese invasion of Taiwan, this issue holds relatively less significance for South Korea than the persistent threat of North Korean aggression.
The USFK Commander acknowledged these divergent priorities in July, stating that "I don't think it should be considered a foregone conclusion that we're saying, 'Hey, if we go to Taiwan, you're going to Taiwan too'." Brunson clarified that "What's being asked of Korea is to be stronger against DPRK—that we might have the flexibility as we modernize our alliance so that we could go do other things."
However, the ambiguous phrase "go do other things" opens the door to multiple interpretations. Even without a reduction in U.S. troop levels on the peninsula, Seoul faces mounting pressure to adopt increasingly confrontational military postures alongside Tokyo and Washington against Beijing.
Such positioning would inevitably antagonize China and damage bilateral relations. Moreover, it would likely provoke stronger responses from Pyongyang and potentially deepen trilateral cooperation between China, North Korea, and Russia—creating a dangerous cycle of regional instability that could spiral into miscalculation and military confrontation.
Complicating matters further, Lee has pledged to secure the transfer of wartime operational control (OPCON) of ROK military forces back to South Korea during his presidency. Yet achieving this goal paradoxically demands that Seoul significantly increase defense investments and military capabilities while deepening coordination with U.S. forces.
This creates an inherent contradiction: while regaining OPCON holds the promise of greater strategic autonomy, the pathway to this idea of military independence requires intensified security commitments with the United States, at least in the short term.
The modernization of the U.S.-ROK alliance reflects broader shifts in great power competition, but Seoul must carefully navigate between alliance obligations and national interests. While Washington's strategic logic focuses on China containment, South Korea's security priorities remain more complex.
President Lee faces the delicate task of maintaining alliance solidarity while preserving strategic flexibility. The stakes extend beyond bilateral relations—miscalculations in this modernization process of the alliance could destabilize the entire Northeast Asian security architecture.
Success will require Seoul to articulate a clear vision that strengthens deterrence on the Korean Peninsula without automatically escalating tensions elsewhere in the region. The challenge lies not in choosing between Washington and Beijing, but in crafting a strategy that serves South Korea's long-term interests while contributing meaningfully to regional stability.