주한미군 역할 재정의: 대만과의 우산 공유?

Abstract

As tension between China and Taiwan continues, major players of the Indo-Pacific region are raising their attention toward the Taiwan Strait. Since the Biden administration, there has been a rumor in Washington that the U.S. could mobilize its troops in the Korean Peninsula to support Taiwan in case of military conflict, and this discourse has become more vivid under the second Trump administration. This brought a serious security uncertainty to South Korea, which strengthened domestic demand for nuclear armament for self-defense ever more. This article will look into the ongoing dispute on the role of U.S. Forces Korea (USFK) beyond the Korean Peninsula and analyze how major players in Northeast Asia would perceive this issue, with extra focus on South Korea, the U.S., and Taiwan.

Introduction

On August 25, 2025, South Korean President Lee Jae Myung met U.S. President Donald Trump for his first South Korea-U.S. Summit. On his flight to Washington DC, he said to reporters that Washington’s demand on USFK’s “strategic flexibility” is “difficult to agree”. Although he pledged to increase South Korea’s defense spending after the summit and commit more to be a proactive partner of the U.S. in the region, his previous comment implies that he is reluctant to see USFK mobilize beyond the Korean Peninsula.

Regardless of Lee’s concern, however, the cross-strait relations have long been a major focus of the White House, maybe even more than North Korea and its nuclear threat. While Trump’s urgent security issues have been mainly Russia (war with Ukraine) and Iran (missile strike on nuclear sites), China has always been at the top list, ever since his first term. Considering Xi Jinping’s commitment to “reunification” with Taiwan, as well as China’s provocative activities around the South China Sea, the East China Sea, and the Yellow Sea, it would be logical for the U.S. to engage accordingly, by readjusting its role and extending its presence in the region.

While South Korea would oppose USFK’s strategic flexibility for obvious reasons, Taipei seems to welcome Washington’s move. For Taiwan, current U.S. standpoint on the cross-strait relations would be the most favorable by far, at least in terms of security and defense. Ever since the U.S. recognized Beijing as the only legitimate government of China in 1979, the U.S.-Taiwan relations have been unofficial and informal, which imposed various hardships on Taipei in global diplomacy. However, as China no longer hides its intent to compete with the U.S. and be more aggressive on the cross-strait relations, the irony of Taiwan winning U.S. protection is becoming more realistic.

USFK Debate & Wartime OPCON Dilemma

The USFK debate of today has been an ongoing issue for some time. During his first administration, Trump used USFK as a leverage to win upper hand in defense spending deal with South Korea. Trump has constantly claimed that the “U.S. is no longer the world’s police”, along with his “America first” policy, and is expressing such idea more bluntly in his second term. While the U.S. still wants to maintain its hegemony, Trump pictures the same world with less responsibility and is shaking conventional alliances both in Europe and Asia. As a result, at least in short term, NATO members in Europe agreed to increase their defense spendings up to five percent of their GDP as part of their tariff deals.

Same pressure applies to South Korea. Although the exact amount was not mentioned, President Lee said he would raise the defense spending and modernize alliance with the U.S. Given his comment on USFK’s strategic flexibility, increasing defense spending and modernization of alliance seem to be Lee’s effort to keep USFK’s role within the Korean Peninsula. North Korea’s rising nuclear capability, in addition to its strengthening ties with Russia and China, is a serious threat that South Korea has to confront, and it is somewhat axiomatic that South Korea wishes to keep U.S. nuclear umbrella on its own.

Although USFK had been one of the heated topics of South Korea’s political debate, it seems that the two sides are agreeing to Lee’s concern at least as of now. For conservatives, the ROK-U.S. alliance is a bedrock of national security, and reduction of U.S. troops in South Korea in any manner is a big concern. The Korean War in 1950 broke out after the U.S. troops withdrew in 1949, and it is still a big trauma for South Korea. The U.S. is still the strongest military power of the world, and besides its nuclear umbrella, airpower and intelligence capability of the U.S. are great assets for South Korean defense.

For progressives, their concerns are based on the fear of South Korea becoming the trigger of the cross-strait conflict. Progressive governments of South Korea so far have adopted a peaceful approach toward North Korea, and for its success, relationship with China is a crucial precondition. Progressives’ concern that if South Korea agrees to USFK’s strategic flexibility (and extend South Korea’s role accordingly), it could provoke Beijing and lead to military conflict with Taiwan, and also South Korea at worst. From their view, USFK’s extended role in the region and South Korea’s compliance are an assertive gesture of “close with U.S., far from China”, which will only make regional dynamics even more unpredictable.

One variable that can affect this ongoing debate would be Wartime Operational Control (OPCON) of South Korea. On August 13, 2025, The State Affairs Planning Committee of Lee government unveiled plans for a complete transfer of OPCON from Washington to Seoul within five years. If Washington’s will to extend both USFK and South Korea’s role in the region is stronger than it seems, there is a chance that Trump could make a “deal” of exchanging OPCON for USFK’s role adjustment. Lee could be put into a dilemma choosing between his policy goal and security concern, and this could bounce back into another unexpected political quarrel: if the will for OPCON is strong, Lee could choose to let USFK be more flexible as Washington pictured; if keeping USFK is stronger, however, he might withdraw his will for OPCON, which will bring political backlash not only by the opposition party, but by his ruling party as well.

Views of Stakeholders

South Korea

South Korea and related experts share concerns on the U.S. shifting its focus away from the Korean Peninsula. Rachel Minyoung Lee, senior fellow at the Stimson Center, assessed that USFK’s diversion in focus might send a wrong signal to Pyongyang. She pointed Kim Jong Un has become more assertive and emboldened, and questioned the timeliness of mobilizing U.S. troops. Without U.S. presence, South Korea falls behind North Korea in terms of asymmetric power. Moreover, as the nuclear debate implies, Seoul wishes to keep Washington’s commitment unless South Korea builds its own nuclear capability.

The issue of OPCON transfer is another variable that puts South Korea in a mixed position toward the U.S. strategic flexibility. In order to retrieve OPCON, South Korea has to “prove” at some point that it is capable of sovereign defense while keeping strategic trust with the U.S. One way to prove South Korea’s defense capability is to support U.S.’s strategic shift and take more responsibility for North Korea. However, Lee Jae Myung, as a leader of opposition party in 2024, criticized that the Yoon administration’s effort to improve ROK-U.S.-Japan partnership has ruined diplomatic relationship with China and claimed that South Korea should not get involved in the cross-strait relations. If his non-engagement stance continues, the U.S. might be more skeptical about the ROK-U.S. alliance in terms of regional security, and the OPCON discourse might not develop as the Lee government proclaimed.

In a nutshell, South Korea wants to keep USFK within the Korean Peninsula with OPCON returned. Clearly this is not what Washington would expect from Seoul. The U.S. will demand more to South Korea as part of its “alliance modernization”, and the time will soon come for South Korea to make a choice.

United States

The U.S. wishes to extend its engagement in the Indo-Pacific by weighing more focus on China. Washington claims that the strategic flexibility is not a decrease of its interest in the Korean Peninsula and expects Seoul and other allies in the region to engage more in terms of security and defense. As China has become a “pacing threat” of the U.S., Washington intends to strengthen deterrence by extending its presence in the East China Sea, and it requires readjustment of the role of U.S. troops not only in South Korea, but also in Japan and nearby Pacific islands.

Some analysts view that the extended role of USFK can be an opportunity to assess South Korea’s sovereign defense capability before returning the OPCON. Clint Work, research fellow at the National Defense University’s Institute for national Strategic Studies, diagnosed that South Korean military seems to be less confident in its own capabilities, while it can – and should – be more responsible for its defense and the retrieval of its “control rod”. Although South Korea heavily depends on U.S. nuclear deterrence, Washington regards Seoul as a much stronger partner and expects South Korea to engage more actively and support U.S. strategy in Northeast Asia, or the Indo-Pacific in a wider sense.

What Washington should keep in mind is that South Korea is relatively conservative when it comes to foreign engagement. In order to fulfill its strategic goals, the U.S. should let South Korea realize that the Taiwan crisis is not an unrelated threat to its own national defense, and Taiwan is an important geopolitical partner that needs protection. To win support, Washington must continue its efforts to convince Seoul that the U.S. will provide nuclear umbrella, while at the same time encouraging South Korean military that its conventional firepower exceeds that of North Korea, which is an important asset for U.S. strategy in the Indo-Pacific as well.

Taiwan

In late March this year, The Washington Post disclosed a secret memo of Pentagon, showing the Defense Department’s will to deter “China’s fait accompli seizure of Taiwan”. Washington officially sticks to a “one China” policy, acknowledging Beijing as a legitimate government and Taiwan as part of China, but the memo indicates that the current administration might think otherwise. A number of former officials and experts in Taiwan welcomed the news, as they witnessed Trump suspending U.S. support for Ukraine.

With Washington behind its back, Taipei is also seeking to strengthen ties with U.S. allies in the region, notably South Korea and Japan. Chihchung Wu, Deputy Minister of Foreign Affairs in Taiwan, emphasized the significance of South Korea-Taiwan relations and proposed Seoul to strengthen strategic cooperation with Taipei. Taiwan knows that the U.S. cannot deter China on its own, and South Korea is hesitant to expand its security engagement. If mobilization of U.S. troops actually happens in Taipei’s favor, it might cause another tension – this time with Seoul – as both governments would compete against each other to keep their security issues as Washington’s prior attention. In this sense, Wu’s proposal can be viewed as an effort to avoid conflict with South Korea on sharing U.S. defense capabilities

In order to forge a pro-Taiwan alignment in the region, Taiwan needs both the U.S. and South Korea. Taipei should convince Seoul that U.S. strategic flexibility is not taking U.S. influence away from the Korean Peninsula, but instead a long-term investment to prevent any possible military conflict in the region. Although it will be Washington’s decision to make when it comes to military operation, it is Taipei and Seoul’s responsibility to cooperate and keep the U.S. focused on the region. However, difference between “special relationship” of Taiwan and the U.S. and so called “ironclad” alliance of South Korea and the U.S. will make it difficult for Taipei to persuade Seoul on sharing U.S. troops, considering South Korea’s complex relationships with China and North Korea.

The Anti-West Alignment: China, Russia, and North Korea

On September 3, 2025, Xi Jinping invited Putin and Kim Jong Un to China’s 80^th Victory Over Japan Day. The three leaders stood side by side at Tiananmen Square, watching the parade together. It was a clear message that Beijing, Moscow and Pyongyang will strengthen their ties against the West, and Kim Jong Un was officially recognized by Xi and Putin as one of the core axes of this alignment. The parade marked the official beginning of the “Neo-Cold War” in the Indo-Pacific, between the anti-West alignment and the U.S. and its like-minded partners.

If the U.S., South Korea and Taiwan align, the anti-West alignment will respond in some way. One possible – and the worst – scenario is that China and North Korea simultaneously take military actions against Taiwan and South Korea, which will split U.S. attention into two. In this process, Russia might also take part by supporting North Korea either directly or indirectly, as a return for North Korea’s military deployment to Ukraine.

In this case, the anti-West alignment has two advantages: geographical proximity with each other and distance from the U.S. Currently, each state has its own front: Russia is at war with Ukraine, China is raising tension at the Taiwan Strait, and North Korea is maintaining hostile position against South Korea. However, the three states are geographically connected, and it gives huge merit in mutual exchange. Furthermore, their distance from U.S. mainland provides more time for them to engage before Washington could promptly respond. The anti-West alignment already knows this from experience, such as China supporting North Korea under UN sanctions and North Korea sending ground troops in support of Russia, and they will maximize their geographical advantages in their competition with the U.S. and its partners.

Conclusion

The U.S., South Korea, and Taiwan must all realize that each has its own priority and be ready to support one another. Washington should give more trust to its allies and partners that it will still lead rules-based order in the region with its capability; Seoul should admit that it cannot have OPCON and keep U.S. troops only in the Korean Peninsula at the same time; and Taipei should understand South Korea’s security dilemma situated between the U.S. and China due to North Korean threat, and be more thorough on its diplomatic approach to win its support.

Alliance is not an ownership. It is a mutual commitment, which is not permanent but subject to change in real politics. A friend today can be an enemy tomorrow, and it depends on how regional or global dynamics develop. No country can only gain without losing in global politics. In order to keep status quo and take the lead in strategic competition, all three – Washington, Seoul, and Taipei – should acknowledge that each has to give something up to some extent and take more responsibility on its own.