Abstract

South Korea’s recent political turmoil, highlighted by the impeachment of President Yoon and the resulting leadership vacuum, has raised serious questions about the country’s democratic resilience and reliability as a U.S. ally. As the U.S. approaches its own presidential transition, South Korea’s domestic political issues will further complicate US–ROK bilateral relations.While the alliance’s institutional strength offers continuity, disruptions to security and diplomatic coordination pose risks. Restoring domestic stability is crucial for South Korea to sustain regional leadership, tackle challenges in U.S.–ROK cooperation, and reinforce the alliance’s pivotal role in maintaining Indo-Pacific security and stability.

In recent weeks, South Korea has entered a period of profound political upheaval. The impeachment proceedings against President Yoon Suk-yeol, following his contentious decision to declare martial law, has exacerbated domestic divisions and cast doubt on the nation’s democratic resilience and its capacity to remain a reliable partner on the global stage. For the United States, South Korea’s political instability emerges at a pivotal moment in the alliance, as heightened security challenges amidst escalating tensions in the Indo-Pacific region coincides with the transition in American presidential leadership.

As the situation in Seoul unfolds, concerns regarding governance, policy continuity, and bilateral cooperation have come to the fore. Will this political crisis divert South Korea from its commitments to the U.S.–ROK alliance, or might it catalyze a recalibration of priorities that ultimately strengthens collaboration? These questions are not merely theoretical but carry significant practical implications for the trajectory of one of the Indo-Pacific’s most vital alliances. The coming months will serve as a litmus test for the alliance’s resilience and ability to navigate concurrent domestic and geopolitical challenges.

Understanding South Korea’s Current Crisis

On December 3, 2024, at 10:27 p.m. Korea Standard Time (KST), South Korean President Yoon Suk Yeol announced martial law in a televised address. He justified the decision by citing the need to protect South Korea from “anti-state activities,” “North Korean communist forces,” and “antistate forces,” as well as to “rebuild and safeguard” the nation from “falling into ruin” (Lim et al., 2024). Additionally, President Yoon accused opposition parties of undermining democracy by impeaching his cabinet members and obstructing the passage of the national budget (Atlantic Council, 2024). This marked the first declaration of martial law in South Korea since 1980, when Chun Doo-hwan seized power in a military coup following the assassination of President Park Chung-hee in 1979 (Lim et al., 2024).

The declaration of martial law immediately triggered widespread protests. At 1:02 a.m. on December 4, 190 members of the National Assembly unanimously passed a resolution to revoke martial law (Coleman, 2024). By 4:30 a.m., President Yoon and his cabinet lifted the martial law order and swiftly disbanded the Martial Law Command. Later that afternoon, at 2:43 p.m., opposition parties formally submitted a motion to impeach President Yoon. On December 14, the National Assembly passed an impeachment resolution against Yoon, accusing him of “insurrectionary conduct” (Atlantic Council, 2024; Park, 2024a). His powers were immediately suspended, and Prime Minister Han Duck-soo assumed the role of acting president until the Constitutional Court could rule on the validity of the impeachment (Park, 2024a). Han sought to reassure the public, pledging to “ensure stable governance” during the transition period (Park, 2024a). However, on December 27, Han faced impeachment, leaving the position of acting president to Finance Minister and Deputy Prime Minister Choi Sang-mok (Kim, 2024; Shin, 2024).

During the period between the impeachment motion and the final impeachment decision, massive protests erupted across Seoul; demonstrators carried banners and chanted slogans condemning Yoon’s declaration of martial law, which many perceived as a blatant attempt to consolidate power and silence dissent. Civil society groups, student unions, and opposition parties mobilized quickly, organizing large-scale rallies that drew international attention. Public sentiment overwhelmingly framed the move as a dangerous slide toward authoritarianism, endangering the democratic principles that South Korea has painstakingly built over the decades (Atlantic Council, 2024). 

South Korea’s Situation Today

Choi, an experienced civil servant with decades of economic decision-making expertise, is currently serving in the unprecedented roles of acting president, acting prime minister, and finance minister (Shin, 2025). In a written statement, he emphasized, “ensuring stable governance is of paramount importance” (Shin, 2025). At this stage, minimizing disruptions in national affairs is the top priority. He further pledged to uphold robust national security, economic stability, and public safety to safeguard the nation’s welfare and ensure that the daily lives of its citizens remain unaffected (Park, 2024b; Shin, 2025). 

At present, resolving political uncertainty and social conflict has become a critical issue for South Korea. Domestic turmoil and ongoing domestic challenges not only threaten to weaken the coherence of South Korea’s foreign policy but could also have profound implications for the country’s governance capacity. Against an increasingly complex global geopolitical landscape, South Korea must achieve internal stability to fill the power vacuum and lay the foundation for enhanced international cooperation.

Implications for Ties with Washington

Some argue that the U.S.–ROK alliance, with its deeply entrenched institutional memory and highly developed mechanisms of cooperation, can swiftly return to a semblance of normalcy in key meetings and working-level coordination, even amid the current climate of political uncertainty (Atlantic Council, 2024). This institutional framework provides a stable foundation for sustained security and defense cooperation while underscoring the alliance’s resilience in responding to external pressures and internal dynamics.

However, the political instability within South Korea has already posed significant challenges to its role and influence in major international affairs. For instance, U.S. Secretary of Defense Lloyd Austin canceled his scheduled visit to South Korea in early December due to the political turbulence (Ali & Stewart, 2024). Similarly, U.S.–South Korea nuclear deterrence negotiations, aimed at strengthening regional security cooperation, were postponed (Ali & Stewart, 2024). These developments highlight South Korea’s vulnerability during periods of political transition and raise concerns about its ability to effectively uphold the regional security framework.

Complicating matters further, on January 20, 2025, Donald Trump was officially sworn in as President of the United States, while South Korea remained under the leadership of an acting president. According to South Korea’s constitutional court procedures, the process from the final ruling on a presidential impeachment case to the election of a new president could take up to eight months. This protracted and uncertain power vacuum casts doubt on the continuity and effectiveness of South Korea’s policies as it faces simultaneous domestic and international pressures.

Victor Cha, the Korea Chair at the Center for Strategic and International Studies (CSIS), remarked that this political upheaval comes at a critical moment, as South Korea’s leadership faces the task of building personal relationships with the new U.S. administration—such relationships are considered “essential” (Korea Joongang Daily, 2024). He further warned that this instability could create “the most unfavorable potential risks” for the onset of a Trump 2.0 administration and the future development of the Seoul–Washington alliance (Korea Joongang Daily, 2024).

The current interim government, lacking sufficient political authority and diplomatic flexibility, risks significantly hindering effective communication between the United States and South Korea. This obstacle could weaken bilateral coordination on regional security challenges and international affairs, making it difficult to align strategic objectives.

Recently, former President Trump publicly announced his intention to meet with North Korean leader Kim Jong-un during a press conference (Al Jazeera, 2025; Martyniuk, 2025). This statement reaffirmed the unique personal relationship between Trump and Kim, which saw three high-profile meetings during his first term from 2018 to 2019 (Al Jazeera, 2025). However, this announcement has raised concerns about a potential weakening of U.S.–South Korea policy coordination on North Korea. Such a development could undermine South Korea’s leading role in addressing issues related to the Korean Peninsula. If South Korea's position is further marginalized, its long-standing role as a vital intermediary between the U.S. and North Korea would face significant challenges.

Moreover, this preference for unilateral engagement risks deepening policy divides within the U.S.–South Korea alliance. As a core issue of the alliance, North Korean policy serves as a key indicator of the strength and adaptability of bilateral relations while carrying profound implications for regional stability. In the coming months, whether the two allies can achieve policy alignment on North Korea will directly impact the stability of their alliance and shape the outlook for peace and security in the region.

To solidify its position as a regional leader, the South Korean government must prioritize restoring domestic political stability, which is fundamental to crafting and implementing effective foreign policy. Political fragmentation at home not only undermines South Korea’s ability to act decisively in international affairs but also diminishes its influence in shaping regional dynamics. By addressing internal challenges and developing a unified strategic vision, South Korea can reclaim its diplomatic initiative and enhance its leadership in critical areas such as security cooperation and multilateral governance.

A proactive and stable South Korea aligns not only with its national interests but also serves as a cornerstone for peace and prosperity throughout the Indo-Pacific region.