U.S.-South Korea Policy Coordination on Maritime Security

On November 14, 2023, the Council on Foreign Relations’ program on U.S.-Korea Policy held an in-person workshop on U.S.-South Korea policy coordination toward China on maritime security. This workshop was made possible by a generous grant from the Smith Richardson Foundation.

Introduction

The May 2021 U.S.-South Korea Leaders’ Joint Statement by U.S. President Joe Biden and South Korean President Moon Jae-in referenced, for the first time, the importance of preserving peace and stability in the Taiwan Strait. Since his inauguration in May 2022, South Korean President Yoon Suk Yeol has strengthened rhetorical support for Taiwan and expanded maritime security policies in the region to protect freedom of navigation and overflight in the East and South China Seas to enhance alignment with the United States and broaden the scope of the U.S.-South Korea alliance beyond peninsular affairs.

In an interview with Reuters in April 2023, President Yoon argued that the Taiwan issue is a global issue and that the international community needs to oppose China’s attempts to change the status quo by force. However, he has also statedthat South Korea’s top priority in the event of a cross-strait military conflict would be to defend against the increased possibility of North Korean provocations and ensure that the United States and South Korea deal with the North Korean threat first. South Korea’s role in a Taiwan conflict and the potential connection between a Taiwan and Korean Peninsula contingency are growing topics of discussion between the United States and South Korea, highlighting the need for enhanced policy coordination on maritime security and growing Chinese assertiveness in the region.

South Korea’s Security Considerations

While President Biden has prioritized strengthening U.S.-Taiwan ties and stated that the United States would defend Taiwan in the event of a cross-strait conflict, the Taiwan issue remains underdeveloped in South Korea’s security policy. The two major factors shaping South Korea’s approach to cross-strait tensions are North Korea and China.

North Korea’s growing military capability is a central concern to South Korean thinking regarding its ability to deter North Korean provocations. In the event of a cross-strait contingency, South Korea could be reluctant to directly participate in the conflict, reasoning that supporting Taiwan would come at the expense of its own security against North Korea. The possibility that a Taiwan conflict could lead to a renewed conflict with North Korea—similar to North Korea’s invasion of South Korea in 1950 that sparked the Korean War—is the primary concern shaping South Korea’s approach toward defending Taiwan.

In addition, South Korea needs to consider China’s potential response to South Korean active support for Taiwan. China’s status as one of South Korea’s top trading partners and the geographic proximity between the two countries create inherent constraints to South Korea’s approach. Compounded by the fact that China and North Korea remain close partners and that China holds a degree of leverage over North Korea, South Korea would likely be reluctant to engage in a direct conflict with China.

South Korea’s role in a cross-strait conflict would also heavily depend on the degree of U.S. involvement and the strength of the U.S.-South Korea alliance. An August 2022 poll conducted by Joongang Ilbo and the East Asia Institute asked South Korean participants about the desired direction of South Korea’s military response to a cross-strait contingency: 42 percent of respondents favored South Korea providing rear support to U.S. military personnel and 22.5 percent supported South Korean military involvement alongside U.S. forces. Thus, the role and leadership of the United States would factor into South Korean military planning and thinking, in addition to whether U.S. Forces Korea (USFK) would be redirected and moved to Taiwan during a conflict. Similar to U.S. leadership in coalition-building in response to Russia’s invasion of Ukraine, the level of engagement among U.S. allies in the Indo-Pacific region would require a strong and credible United States.

Recommendations

• The United States and South Korea should develop a joint strategic framework that addresses maritime security concerns in the Taiwan Strait and South China Sea. Such an agreement would align U.S. and South Korean stances, expectations, and operational planning.
• The United States and South Korea should establish bilateral or multilateral mechanisms for maritime crisis management. The joint protocols should coordinate ways in which U.S. and South Korean forces can prevent or de-escalate maritime crises.
• The U.S. government should continue exhibiting strong leadership on the Taiwan issue but remain flexible toward allies with high economic interdependence with China. For allies such as South Korea that align with the United States based on shared ideology and values, the United States should maintain its values-based leadership in the region. However, the United States should take into consideration the views and risk exposure of allies who could be vulnerable to collateral security risks in the event of a regionwide expansion of a cross-straits conflict.

Strengthening Ties Between South Korea and Taiwan

A survey by Seoul National University’s Asia Center of South Korean perceptions of regional countries in 2022 showed that 47.3 percent of participants favored Taiwan as a credible partner, but Taiwan ranked eighth on the list of countries that South Korea should strengthen cooperation with. Since diplomatic ties between South Korea and Taiwan ended in 1992, public affinity and the level of bilateral engagements between the two countries remain limited. While public perception of Taiwan is largely positive in South Korea, it is unclear whether public favorability will translate into strong public desire for South Korea to militarily support Taiwan during a potential conflict. North Korea remains the most pressing security concern for South Koreans, making involvement in a cross-strait conflict a relatively new and distant issue for many in the public. As a democratic country, public sentiment will greatly influence the South Korean government’s actions in a Taiwan contingency. Thus, highlighting the importance of Taiwan to the South Korean population will allow for greater public engagement and interest on the Taiwan issue.

In addition, there are various opportunities for both countries to increase military ties and broaden multilateral venues for greater political and regional engagement. South Korea and Taiwan currently do not hold joint military exercises, nor do they have regular high-level military dialogues. The South Korean government could be reluctant to openly explore military exchanges with Taiwan given the potential for Chinese backlash. Regional forums in which South Korea and Taiwan are both participants could offer a less risky pathway for strengthening bilateral ties. Some participants noted that regional groupings such as the Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP) or U.S.-led initiatives such as the Global Cooperation and Training Framework (GCTF) could offer multilateral venues that boost mutual understanding and bolster cooperation between South Korea and Taiwan without impinging on the issue of Taiwanese sovereignty.

Enhancing people-to-people, military, and regional engagement between South Korea and Taiwan will be a critical element shaping the level and extent of South Korean support in a potential cross-strait conflict. As South Korea exhibits greater willingness to support U.S. efforts in the Indo-Pacific region, broadening bilateral ties between South Korea and Taiwan will buttress South Korean desires to preserve stability in the Taiwan Straits.     

Recommendations

• The South Korean government should increase public education about Taiwan’s cultural, economic, and strategic importance. In particular, there should be a greater number of initiatives and forums that raise public awareness of the potential connectivity between Taiwanese and South Korean contingencies and links between the two countries’ securities.
• South Korea should strengthen cultural exchanges and tourism with Taiwan to raise its profile among the South Korean public and bolster people-to-people ties.
• South Korea should continue pursuing regional initiatives as part of its goal of being a global pivotal state and its status as an ally of the United States in the Indo-Pacific region. Such efforts could involve deepening engagement with Association of Southeast Asian Nations (ASEAN) countries to build collective resilience and enhance regional economic stability, as well as strengthening relations with other U.S. regional allies such as Australia and New Zealand. 
• The United States should take greater advantage of its convening power to invite South Korea and Taiwan to the same multilateral forums and intergovernmental organizations.

Stakes for the U.S.-South Korea Alliance

A cross-strait contingency could serve as a stress test for the U.S.-South Korea alliance if there are gaps between the level of support provided by the United States and South Korea. South Korean hesitation and restraint could have significant implications for the U.S.-South Korea alliance in the event that the United States assumes a leading role in building a coalition to support Taiwan. However, participants disagreed on whether a limited South Korean role would impact the alliance. Some participants argued that the U.S.-South Korea alliance could end if South Korea were unwilling to assume active involvement in a cross-strait conflict or if the South Korean government refused to lend either South Korean or USFK troops to defend Taiwan. This could lead U.S. policymakers to question the value of the alliance. Other participants countered by suggesting the South Korean military and USFK have limited relevant resources to lend Taiwan during a conflict, but noting that South Korea could be willing to provide rear support, which would allow South Korea to support Taiwan without committing to on-the-ground troop or material assistance.

However, some participants pointed out that the United States may not lean on or pressure South Korea to lend support in a Taiwan contingency due to the concept of strategic flexibility of USFK and the potential for a dual contingency with North Korea. During the first session of the U.S.-South Korea Strategic Consultation for Allied Partnership in January 2006, U.S. Secretary of State Condoleezza Rice and South Korean Foreign Minister Ban Ki-moon outlined the two countries’ positions regarding the issue of strategic flexibility of USFK. While South Korea noted its understanding and respect for the need for strategic flexibility, the United States stated its respect for South Korea’s position that USFK “shall not be involved in a regional conflict in Northeast Asia against the will of the Korean people.” Participants questioned whether the concept of strategic flexibility remained the operative understanding of the Biden and Yoon administrations and if it reflected the current thinking of both countries regarding off-peninsular contingencies in the region. In addition, discussing the possibility of North Korean opportunism in the event of a Taiwan contingency and the potential for a two-front conflict raised the question of whether the ideal U.S.-South Korean posture would be to view the Korean Peninsula exclusively as a rear base of support or anticipate direct participation of South Korean combatants in Taiwan.

In-depth discussions on the role of USFK and South Korean military personnel during a Taiwan conflict are needed to ensure U.S. and South Korean defense planners do not have different expectations, risking damage to the U.S.-South Korea alliance. As the scope of the U.S.-South Korea alliance expands beyond the Korean Peninsula to tackle regional and global security challenges, the response of both countries to a cross-strait contingency remains an important policy concern requiring greater coordination and communication.

Recommendations

• South Korean scholars and public officials should actively discuss the potential spillover effects of a Taiwan conflict as related to both the impact on the Korean Peninsula and Japan’s role. Tabletop exercises should incorporate the possibility of a two-front war in which both the Taiwan Strait and Korean Peninsula become involved in crises.
• The United States and South Korea should clarify whether the two countries will reaffirm the concept of strategic flexibility in the event of a Taiwan contingency or maintain U.S. strategic forces in South Korea to prevent North Korean opportunism.