1 Introduction

Following the 2008 financial crisis, East Asia witnessed a significant power shift characterized by the rapid growth of China and the relative decline of the United States. Given the relative decline of US hegemony and its inadequate supply of strategic resources, countering the rise of China and maintaining its dominant position in the Asia–Pacific region has become a pressing strategic issue for the US. As an essential strategic channel into the Asia–Pacific region, the Asia–Pacific alliance system has become a crucial strategic instrument for the US in the current Sino-US rivalry. The US has urged its allies to bear a more significant share of strategic costs and alliance obligations.

South Korea is unquestionably responsible for sharing its obligations as a vital ally of the US in the Asia–Pacific region. As the strategic competition between China and the US intensifies, US pressure on South Korea has risen significantly. Throughout the Trump administration, the US warned of a potential withdrawal of American troops stationed in South Korea, urging South Korea to take on a more significant share of defence responsibilities. Following the inauguration of President Biden, the US went on to request that South Korea align with its decoupling efforts from China in the areas such as high-tech and the economy, irrespective of the significance of the economic ties between China and South Korea. While the Biden and Trump administrations have placed varying emphasis on different areas and approaches, they share the same fundamental objective: to urge South Korea to undertake more outstanding alliance obligations and establish its position as a linchpin in Northeast Asian and Asia–Pacific security.

Given the prevailing circumstances, how does South Korea, the minor partner in the alliance, respond to the pressure exerted by the dominant partner? What are the determinants that will impact the alliance management strategy of South Korea? Is South Korea capable of efficiently handling the influence exerted by the United States?

The transformation of US alliances in the Asia–Pacific has long been a topic of interest within academic discourse. Scholars have been examining the challenges faced during the conversion of the US alliance and its strategies for alliance management, primarily through the lens of the dominant state. The US is confronted with several alliance dilemmas, including but not limited to the predicament of commitment, the trade-off between cost and risk, the intra-alliance conflict, and the double dilemma. In response, the US has utilized various tactics, including coercion, institutional constraints, interest alignment, and authority’s direction, to manage its alliances proficiently (Zuo 2015; Zhou 2019). These studies provide a crucial theoretical foundation for comprehending the transformation of US alliances. However, the response strategies of minor states also play a significant role in transforming US alliances.

A comprehensive understanding of the strategies employed by the minor states is required to better assess the evolution and development of the alliance system from a broader perspective. Nonetheless, research on minor states’ responses to pressure from the dominant state in asymmetric alliances is limited (Castillo 2023; Jiang 2022). Based on existing studies, this paper uses the US–ROK alliance as an example to analyse the alliance dilemma faced by South Korea and the evolution of its response strategies as the minor partner of the US–ROK alliance, as well as factors influencing these strategies. In terms of policy, this research provides a deeper understanding of the interaction within the US–ROK alliance and the trajectory of its transformation.

2 The challenges faced by South Korea: pressure from the dominant ally

In the realm of international relations, forming alliances presents distinct security challenges, namely alliance dilemmas and alliance management issues. Glenn H. Snyder employs the notions of ‘abandonment’ and ‘entrapment’ to advance a theoretical framework on the security dilemma in alliance politics. ‘Entrapment’ in Snyder’s terminology refers to the situation of being embroiled ‘into a conflict over an ally’s interests, despite not fully or completely sharing those same interests, which can result in significant losses to the country’s own interests; the notion of ‘abandonment’ pertains to instances of ‘defection,’ where allies fail to uphold their commitments, provide support, or even abrogate the alliance contract or align themselves with adversaries, thereby leaving the country in a state of isolation (Snyder 1984).

The US–ROK alliance has been characterized by a long-standing, mainly unidirectional concern regarding the risk of ‘entrapment.’ Specifically, the US is more concerned about being ‘entrapped,’ while South Korea has primarily been concerned with the possibility of being ‘abandoned.’ However, the evolving Sino-US competition and Sino-ROK relations, coupled with South Korea’s burgeoning power, have shifted the alliance dilemma within US–ROK relations. As a result, South Korea is now confronted with a heightened risk of ‘entrapment.’ The current situation reveals two primary expressions of South Korea’s concern regarding ‘entrapment.’

First, South Korea’s strategic options are limited due to the possibility of being drawn into a major power rivalry. The Sino-US rivalry is the basis for the current US–ROK alliance adjustment. The evolving power shift between China and the US may have negative implications for South Korea’s economic interests vis-à-vis China, as the US insistence on taking sides could result in unnecessary economic costs for South Korea. Since the establishment of diplomatic relations between China and South Korea, the two nations have continued to forge closer connections. Regarding economic and trade ties, China has emerged as South Korea’s primary trading partner, export market, source of imports, target country for overseas investment, and overseas travel destination (Global Times 2022a). Bilateral trade between China and South Korea in 2020 amounted to US$285.26 billion. Chinese imports accounted for over 60% of the total bilateral trade, resulting in a trade deficit of over US$60 billion (Ministry of Commerce, China 2020).

Furthermore, South Korea significantly relies on China in terms of critical strategic resources. This includes dependence on China for magnesium ingots, which are essential for producing automobile bodies. South Korea’s dependence on China for tungsten oxide, a vital material in the production of medical devices and semiconductors, stands at 94.7%, while the country’s dependence on China for a substantial number of industrial raw materials has surpassed 90% (Korea Trade News 2021).

Undoubtedly, the deterioration of Sino-ROK relations will hinder the growth of the South Korean economy. The deployment of Terminal High Altitude Area Defense (THAAD) systems has exemplified the potential negative consequences for South Korea’s involvement in the rivalry between the US and China. Particularly, the deployment of the THAAD anti-missile systems by US forces in Korea, which has resulted in significant economic losses for various domestic industries in South Korea (Cankao Xiaoxi 2017). The United States’ recent efforts to promote a ‘semiconductor alliance’ have raised concerns in South Korea. Specifically, there is apprehension that if South Korea fully aligned itself with the US and joined the US-led global semiconductor supply chain, it might face retaliatory measures from China, including but not limited to the prohibition of core raw material exports for semiconductor manufacturing to South Korea. Moreover, given that South Korean semiconductor companies are actively engaged in global mergers and acquisitions, there is a possibility that China may deliberately postpone relevant review and approval processes (Global Times 2022b).

The second concern is that South Korea may find itself compelled to engage in conflicts that extend beyond the confines of the Korean Peninsula, thereby being situated in the hazardous ‘frontier’. The disparity in interests between the US and South Korea is determined by their asymmetrical relationship, whereby the former holds a dominant position and has global interests, while the latter, as the minor partner, is primarily concerned with interests confined to the Korean Peninsula. Consequently, several global strategic initiatives undertaken by the US have been outside the national interests of South Korea. Despite these conflicting interests, South Korea has often found itself compelled to participate in such initiatives. This raises the possibility of South Korea being entrapped in irrelevant alliance activities, as well as South Korea’s anxiety about this possibility.

The networking and institutionalization of the US alliance system and establishing the ‘comprehensive strategic alliance’ between the US and South Korea have increased the risk of South Korea being entrapped in hostilities in the Asia–Pacific region. Specifically, the US–ROK agreement in 2006 regarding the strategic flexibility of US Forces in Korea has broadened the forces’ responsibilities and extent of involvement. Furthermore, further deployment of the US anti-missile system in South Korea, as well as South Korea’s cooperation with the US and other allies in various areas, including military procurement, defence cooperation mechanisms, and intelligence sharing (Li 2022), provide both a legal foundation and an army readiness for USFK to carry out missions beyond the peninsula.

South Korea recently involved in three regional conflicts: the South China Sea, Taiwan, and Russia–Ukraine. The US re-engagement in the Asia–Pacific region has heightened tensions regarding the issue of the South China Sea. The US has promoted the concept of ‘freedom of navigation’ to justify engaging its allies and other foreign nations in the South China Sea dispute. Despite not being a direct participant in the conflict, South Korea has emerged as a significant focal point for the US in the Asia–pacific region, owing to the potential impact of the South China Sea dispute on US maritime trade routes and the strategic position of South Korea as an important ally within the region. The US has requested that South Korea express its stance on the South China Sea through multiple channels. During a joint press conference for the US–ROK summit, then-President Obama expressed his desire for President Park Geun-Hye to urge China to adhere to international norms and laws. He further suggested that if China failed to do so, South Korea should voice its concerns. The Trump administration requested that South Korea assume a more significant role in the ‘Indo-Pacific strategy’ of the US, which entailed deploying naval vessels to disputed islands in the South China Sea to assert its influence (Guanchanet 2019).

Apart from the South China Sea dispute, the US has persistently urged South Korea to take a stance on the Taiwan issue and to exert pressure on China. Since 2021, the US and South Korea have consistently expressed official stances regarding Taiwan issues in bilateral and multilateral discussions. In addition, intervention by USFK in the Taiwan issue is crucial for the US to effectively exert pressure on South Korea. During a recent television interview, President Joe Biden reiterated his stance on the ‘protection of Taiwan’. General Paul LaCamera, the commander of USFK, has also stated that contingency planning for the force’s involvement in the Taiwan Strait is under development. When an incident occurs in this area, the forces will intervene if necessary.

Meanwhile, the US will encourage South Korea’s involvement in related operations (Yonhap News 2022a). And the former Secretary of Defense Mark Esper expressed that in the event of a contingency in the Taiwan Strait, both USFK and South Korea would play a support role (The Dong-A Ilbo 2022). As a result, South Korea would become an essential base for US military intervention in the Taiwan issue. In this regard, South Korea’s concern is twofold. First, if a conflict were to arise in the Taiwan Strait, the distraction this would create for USFK would result in a gap in the defence posture against North Korea. This raises the question of who should be held responsible for addressing the potential adverse consequences of such a scenario. Second, who would bear the responsibility if USFK entrapped South Korea in the Taiwan Strait conflict, resulting in retaliation by mainland China on South Korea? (Hankyoreh 2022)

During the Ukraine crisis, the US requested that South Korea provide armaments and even offered to deliver them (The JoongAng 2022). The US also asked that South Korea participate in sanctions against Russia (The Kyunghyang Shinmun 2022). In response to external pressures from the US and its allies, South Korea has implemented sanctions against Russia (The Chosun Ilbo 2022a). South Korea also extended military support to Ukraine, including bulletproof helmets, tents, blankets, military rations, camp beds, and other related equipment. Personal emergency kits, medicines, and other medical supplies have also been provided. The total value of military aid from South Korea has already amounted to hundreds of millions of dollars. However, South Korea has declined Ukraine’s appeal for air defence systems and expressed reservations about supplying anti-personnel weapons, indicating a desire to maintain flexibility in its dealings with Russia. According to Russian President Vladimir Putin, the decision made by South Korea to supply arms and ammunition to Ukraine may negatively impact the relationship between the two nations (Yonhap News 2022b).

3 The evolution of the response strategy of South Korea: from seeking autonomy to reinforcing alliance

Orienting toward alliance or autonomy has become a significant point of contention in South Korean diplomacy as the nation’s power continues to increase (Han 2004). There has been constant debate between two parties: the autonomy faction contends that South Korea must reduce its overreliance on the US and that its military capabilities are sufficient to ensure its security, while conversely, the alliance faction advocates for the continual strengthening of the US–ROK alliance and its expansion beyond the Korean Peninsula (Shin Donga 2017). Hence, the alliance management strategy of South Korea faces a dilemma between prioritizing autonomy or alliance. South Korea must decide whether to reinforce the coalition or prioritize autonomy within the alliance’s framework.

Currently, South Korea is experiencing pressure from the US to take on greater alliance obligations, resulting in an evolutionary shift in its response strategy from seeking autonomy to reinforcing the alliance with the US. The final stage of the Moon Jae-in administration marks a pivotal moment in the recalibration of South Korea’s alliance strategy.

3.1 Seeking autonomy

Facing pressure from the US, South Korea opted to enhance its autonomy within the US–ROK alliance framework under the administration of Moon Jae-in. South Korea’s efforts to improve its autonomy entailed promoting the de-escalation of tensions with North Korea and bolstering its military capabilities to reduce the risk of ‘abandonment’. As the possibility of ‘abandonment’ has decreased, South Korea has had a greater say within the US–ROK alliance, reducing the likelihood of ‘entrapment’.

In comparison to the preceding period, South Korea’s inclination towards autonomy has significantly increased. First, South Korea emphasized its leading role in addressing the North Korean issue. For South Korea, the North Korea issue continues to be a central concern in all of its foreign policy pursuits, as there is no comprehensive resolution in sight. Despite the systemic rivalry between the US and China, the primary security concern for South Korea continues to be the threat posed by North Korea. Moon Jae-in’s inauguration as the President of South Korea coincided with a tricky time in South Korean diplomacy, marked by persistent tensions surrounding the North Korean nuclear crisis, a significant escalation in the US–DPRK conflict, and a notable surge in the possibility of military conflict. Moon’s administration emphasized the importance of South Korea taking a prominent role in addressing the issue of North Korea, advocating for peace and preventing conflict on the Korean Peninsula. In regard to the issue of North Korea, Moon has repeatedly referred to the phrase ‘putting Seoul in the driver’s seat’, which emphasizes South Korea’s leadership role in shaping its North Korean policy. During his National Liberation Day speech in 2017, he explicitly expressed that South Korea should take the initiative to resolve the Korean Peninsula’s nuclear issue (Cheongwadae 2017). During the US–ROK summit, Moon clarified that South Korea should unite the Korean Peninsula (Yonhap News 2017).

Moon vowed to enhance South Korea’s leadership in its policy towards North Korea through summit diplomacy, sending envoys, and high-level reciprocal visits, thereby promoting policy coordination with the US. Moon’s diplomatic efforts have seen reduced tensions between the US and North Korea, resulting in a shift in the Trump administration’s stance towards North Korea and an acceptance of South Korea’s proposal for dialogue. Following that, the leaders have held summit meetings in Singapore, Vietnam and Panmunjom to exchange views on issues related to the Korean Peninsula. And both the US and North Korea acknowledged the role played by South Korea.

Second, South Korea enhanced its independent defence capabilities. South Korea has identified three primary justifications for its belief in enhancing its autonomous capabilities. To start with, against the backdrop of the ongoing power shift in East Asia and the strategic contraction of the US, South Korea began to question its strategic commitments of the US. This has cast doubt on the reliability of the US–ROK alliance (Kim 2015). Meanwhile, South Korea held the view that the global community has been undergoing a significant transformation, characterized by the decline of multilateralism and the rise of nationalism. In light of the evolving circumstances on and around the Korean Peninsula, South Korea needed to enhance its defence capabilities and bolster its strategic significance (Cheongwadae 2019a). Second, South Korea believed that maintaining its national security forces helped increase security provisions from its allies, as anticipated by the US. This move could enhance South Korea’s role in the US alliance system, and ultimately the ROK–US alliance would be further valued and strengthened (Cheongwadae 2019b). Thirdly, by reinforcing South Korea’s autonomy in the US–ROK alliance and establishing a collaborative US–ROK defence mechanism with South Korea playing the leading role, the strategic objective of enabling South Korea to take charge of the defence of the Korean Peninsula in the future could be achieved (Moon 2019).

Following the inauguration of Moon Jae-in, he put forth a national security strategy centred on the concept of ‘responsible national defence’ as a means of attaining security. Establishing a ‘collaborative US–ROK defence system under the leadership of the South Korean military, as well as the reinforcement of the defence force of South Korea,’ are crucial strategic considerations in achieving the goal of ‘responsible national defence’. The Moon Jae-in administration put forth the ‘National Defense Reform 2.0’ plan to establish a ‘powerful army’. The term ‘powerful army’ refers to ‘an army capable of taking the lead in responding to all-round security threats’, ‘an elite army based on cutting-edge science and technology’, and ‘an army that aligns with the characteristics of an advanced nation’ (Ministry of National Defense, ROK 2018, 38-39). Specifically, this implies regaining wartime operational control as soon as possible. South Korea increased its defence expenditure, focusing on enhancing its capacity to intercept ballistic missiles launched by North Korea and establishing the Korea Air and Missile Defense (KAMD) system to bolster its ability to respond to security threats from North Korea. During the 5-year tenure of the Moon Jae-in administration, South Korea’s military expenditure has risen by 36.9 percent, surpassing any preceding administration (Hankyoreh 2021a). According to the World Military Strength Rankings released by the US military power evaluator Global Firepower (GFP), South Korea’s ranking has risen significantly from 11th place in 2015 to 6th place in 2020.

Finally, South Korea also sought to achieve relative autonomy in its foreign relations. Moon remarked that South Korea should maintain friendly relations with China and not be forced to choose between the US and China. Regarding the THAAD issue, he adopted the ‘Three Nos’ position and proactively sought to mend the relationship between South Korea and China. The Moon Jae-in administration aimed to avoid further entanglement in other major power rivalries within the Asia–Pacific area. The notion of ‘The Indo-Pacific Strategy’ introduced by President Trump during his 2017 visit to South Korea was not included in the ensuing ‘United States–Republic of Korea Leaders’ Joint Statement’. Moon also declined the proposition to elevate military cooperation between the US, Japan, and South Korea to a trilateral military alliance. He asserted that the current military collaboration between the three nations was adequate to address any military provocations from North Korea. Upgrading it to a military alliance could potentially harm the relationship between South Korea and China and could also serve as a justification for the remilitarization of Japan.

3.2 Reinforcing the alliance

However, towards the final stage of the Moon Jae-in administration, South Korea transitioned from its prior pursuit of autonomy to a comprehensively reinforcing alliance. In May of 2021, after discussions between Moon and Biden, a joint statement by the US and South Korea was released, which served to reiterate the ironclad alliance between the two countries and characterized the alliance as ‘the linchpin for both regional and global order’. South Korea started collaborating with the US in various domains and facilitated the augmentation of the US–ROK alliance across diverse spheres and regions. Following this, the Yoon Suk-Yeol administration presented a diplomatic path to comprehensively enhance the US–ROK alliance and actively advocated for the ‘upgrade’ of the alliance. South Korea has improved its cooperation with the US in various areas and expanded the extent of such collaboration.

First, in addition to security, South Korea has augmented its collaboration with the US in the economic and technological domains. In April 2021, a trilateral meeting of national security advisors was held among the US, Japan, and South Korea to discuss cooperation in securing the semiconductor supply chain and stress its importance. At the subsequent US–ROK summit meeting, the US and South Korea signed an agreement on semiconductor industry chain cooperation and decided to strengthen supply chain integration in areas such as semiconductors, automotive batteries, and electric vehicle production. The US and South Korea also agreed to enhance cooperation in foreign direct investment, export control of fundamental technologies, nuclear energy, space exploration, 5G, 6G, etc. KT and SK, two Korean telecommunications titans, participated in the US ‘Clean Network Plan’ in December 2020. In May 2021, the ‘American Semiconductor Innovation Coalition’ was founded, comprising companies from the US, Japan, South Korea, and other countries or regions. The participants of this coalition represent the entirety of the semiconductor industry chain. And according to Park Young-sun, the Minister of SMEs and Startups in South Korea, the US–ROK alliance should be upgraded to an economic partnership (Yonhap News 2021a).

The Yoon Suk-yeol administration has decided to establish a regular US–ROK Supply Chain and Commercial Dialogue (SCCD), further underscoring the significance of collaboration between the two nations in the industrial chain. And the two nations have enhanced their cooperation in advanced technologies. Following the inauguration of the Yoon Suk-Yeol, South Korea has expressed its commitment to strengthening collaboration with the US in various domains, including advanced semiconductors, environmentally friendly electric vehicle batteries, artificial intelligence, quantum technology, biotechnology, emerging fields such as robotics, and defence sectors. Furthermore, considering the changes in the global energy market brought about by the crisis in Ukraine, the US and South Korea have decided to enhance their collaboration in the realm of energy security, encompassing domains such as sustainable energy and nuclear energy.

By strengthening US–ROK economic ties, South Korea is trying to reduce its economic dependence on China. The Ministry of Industry, Trade and Energy submitted a report titled ‘Changes in the Structure of ROK–China Trade due to the US–China Trade Dispute’ to the National Assembly. The report recommended a policy of diversifying export markets and moving essential critical facilities to South Korea to reduce its export dependence on China (Asia Today 2021).

South Korea has strengthened its partnership with the United States not only in areas such as the economy and technology, but also in terms of shared values. The frequency of discussions about matters on US–ROK leaders and high-level summits has notably risen compared to years past. Moon Jae-in consistently emphasized the importance of values-oriented collaboration with the US. The joint statement of the US–ROK ‘2 + 2’ meetings and the summit between the US and South Korea emphasized a commitment to strengthening endeavours that address advancing democratic principles and human rights, both domestically and internationally.

Second, South Korea has been seeking to broaden the scope of the US–ROK alliance. The joint statements of the US–ROK ‘2 + 2’ meetings and the US–ROK summit in 2021 illustrate that the US–ROK alliance serves as the linchpin for peace, stability and prosperity in the Korean Peninsula and Asia–Pacific region. It also highlights how the significance of the US–ROK relationship extends far beyond the Korean Peninsula. South Korea has also become more active in terms of US–Japan–ROK security cooperation. In 2021, the Meeting of the United States, Japan, and the Republic of Korea Trilateral National Security Advisors was held on April 2nd. The trilateral intelligence community of the three countries held a meeting in May, followed by the meeting of the trilateral deputy foreign ministers in July. The meetings reaffirm the significance of trilateral collaboration in tackling the COVID-19 pandemic, climate change and countering threats to the ‘rules-based international order’. The Yoon Suk-yeol administration has expressed South Korea’s interest in expanding its involvement beyond the Indo-Pacific region, highlighting the significance of the comprehensive global strategic partnership between the US and South Korea. He also reiterated the importance of upholding the ‘freedom of navigation’ principle in the waters, including the South China Sea (The Chosun Ilbo 2022b).

Regarding the ‘Indo-Pacific Strategy’ proposed by the US, the Moon Jae-in administration, which assumed office in May 2017, explicitly declined to endorse the said strategy. However, starting in 2019, South Korea has been promoting its ‘New Southern Policy’ in alignment with the US Indo-Pacific Strategy. During the summit between South Korea and the United States in June 2019, Moon expressed that both nations have agreed to enhance cooperative efforts between South Korea’s ‘New Southern Policy’ and the US ‘Indo-Pacific Policy’ (The White House 2019). Following this, the corresponding ministries of both nations initiated discussions to align their respective policies. Since then, significant advancements have been made in areas such as development, energy, infrastructure, smart cities, law enforcement, cyber security, and cooperation on the Pacific Islands. The South Korean Foreign Minister, Chung Eui-Yong, stated in March 2021 that ‘South Korea is willing to engage in collaborative efforts with any regional cooperation mechanism, including the US, Japan, India, and Australia, provided that the relationship is characterized by transparency, openness, inclusivity, and adherence to international norms.

The Taiwan issue has been a sensitive topic in Sino-ROK relations. Over the three decades since the establishment of diplomatic ties between China and South Korea, consecutive administrations of South Korea have refrained from publicly expressing their stance. However, during the US–ROK summit in May 2021, a joint statement was issued wherein South Korea made a public declaration regarding ‘the importance of preserving peace and stability in the Taiwan Strait’. This marked the first instance of South Korea’s acknowledgement of the Taiwan issue in a public statement. On May 23rd, Choi Jong-Kun, the first vice minister of Foreign Affairs of South Korea, asserted that preserving peace and stability in the Taiwan Strait directly impacts South Korea’s national interests. And during the US–Japan–South Korea vice-ministerial meeting held on July 20th, three nations reiterated the significance of maintaining peace in the Taiwan Strait.

Following Yoon Suk-yeol’s inauguration, there has been an escalation in South Korea’s efforts to promote the integration of the US–ROK alliance. Recent developments, such as the formation of the ‘US–ROK Technology Alliance’, accession to the ‘Indo-Pacific Economic Framework for Prosperity’, and the presence of South Korean leaders at the NATO summit for the first time, all indicate a discernible shift in the South Korean government’s alignment towards the US.

In addition to making a bold gesture towards the US, South Korea has also begun to prepare for the consequences of the impact on Sino-ROK relations. For example, since China and South Korea established diplomatic relations, their economic and trade ties have strengthened. In particular, South Korea’s import and export trade with China has quickly become the largest contributor to South Korea’s foreign exchange earnings. In response, discussions have emerged in South Korea regarding reducing economic reliance on China.

4 Reasons for the evolution of South Korea’s alliance management strategy

In response to pressure from the US to assume more alliance obligations, South Korea’s alliance strategy has shifted from seeking autonomy to strengthening the alliance. South Korea’s shift in strategy is significantly influenced by several factors, including their concern about a potential decoupling from the United States, the conservative nature of South Korean society, and the impasse in South Korea’s policy towards North Korea.

Based on the asymmetrical structure of the US–ROK alliance, South Korea continues to fear potential ‘abandonment’ by the US. The US has long served as South Korea’s military protector, political leader, and economic benefactor, which has entailed building the foundation of its defence forces, providing security, laying the groundwork for economic revitalization, and even intervening in its internal affairs to promote political democratization. Given that the US–ROK alliance is characterized by South Korea’s high reliance on the US, South Korea is frequently finds itself exposed to the alliance dilemma of ‘abandonment’ by its American ally. While the pressure from the US presents South Korea with the issue of ‘entrapment’, the country’s primary concern regarding the structure of the US–ROK alliance is still ‘abandonment.’ The reasons are threefold:

First, North Korea’s advancements in nuclear missile technology have elevated South Korea’s concerns about the possibility of decoupling from the US. In October 2006, North Korea conducted its first nuclear test at the Punggye-ri nuclear test site. In September 2017, North Korea conducted its sixth nuclear test, which marked a significant escalation in its capabilities compared to the previous five tests. In November 2017, North Korea conducted a successful test launch of the Hwasong-15 intercontinental ballistic missile. This particular ICBM can be equipped with a super-heavyweight nuclear warhead, which would place the whole US territory within its reach. During Kim Jong-un’s New Year’s address in 2018, he declared the ‘completion of establishing the national nuclear force’, and unveiled plans for its mass production and operational deployment. The summary report on the 8th Congress of Workers’ Party of Korea (WPK) in January 2021 included indications regarding downsizing, lightweight, and the tactical weaponization of nuclear weapons. The report also mentioned the potential use of these weapons on the Korean Peninsula (The Rodong Sinmun 2021). Regarding submarine launch capabilities, a Sinpo-class submarine equipped with submarine-launched ballistic missiles (SLBM) was launched in 2014, followed by the successful launch of the Pukguksong-1 in 2016. 2019 the Pukguksong-3 was successfully launched from a Sinpo-C-class submarine (Kim 2015).

As North Korea’s nuclear missile capabilities continue to advance, the question arises of whether the US is willing to assume the risk of nuclear war to safeguard its ally, South Korea, which is situated thousands of kilometres away. Had North Korea invaded South Korea in 2000, the US would have deployed military forces to the Korean peninsula to safeguard Seoul. However, given the current circumstances where such an action could potentially result in a nuclear strike on American territory, it remains uncertain whether the US would uphold its alliance obligation to South Korea (The JoongAng 2020). After the two ‘Trump–Kim’ summits ended without concrete results, Moon was eager for more proactive measures from the US to break the impasse. However, the US declined to offer any compromises regarding the cessation of North Korea’s nuclear program. This stance heightened South Korea’s concerns of ‘abandonment’.

Meanwhile, the US strategic contraction has decreased the credibility of US strategic commitments and security assurances, intensifying the ambiguity of the US–ROK alliance. Since 2017, the "America First" policy has significantly affected the stability of the global order and international laws. The decline of US strategic credibility and leadership on the international stage has had tangible effects on South Korea, given its reliance on security protection and global order led by the US. Trump criticized allies of the US as free-riders, which led to uncertainties in the US–ROK alliance as free-riding by allies is no longer acceptable under the ‘Trump Doctrine’. Regarding security, the US adopted a more stringent position regarding cost-sharing for defence services provided by USFK and even threatened to withdraw its troops from South Korea. The foreign policy of ‘America First’ resulted in heightened ambiguity within the US–ROK alliance.

As Japan–South Korea relations deteriorate, Japan has been actively cooperating with the US to besiege China, and the two nations are displaying a new level of intensified cooperation on China-related issues. If South Korea fails to provide support to the US comparable to that of Japan, it will face the possibility of abandonment by the US. For its part, the US has exerted pressure on Japan and South Korea, implying that if the two countries continue to pause in the future, the US would emphasize the Quadrilateral Security Dialogue without South Korea (The Dong-A Ilbo 2021). In addition, Trump’s adopted an ambiguous posture in the Japan-South Korea trade dispute, in which he stated that the two nations should resolve the dispute independently through diplomatic means. These factors have heightened concerns in South Korea about ‘abandonment’ by the US.

Second, with regard to domestic politics, South Koreans’ growing unfavourable view of China has raised concerns about ‘abandonment’ rather than ‘entrapment’. This has undoubtedly affected the perception of China by the Moon Jae-in government. South Korean people’s favorability towards China has been low since the THAAD dispute, and their feeling towards China became even more hostile after the breakout of the COVID-19 pandemic. In 2021, a survey was conducted by a South Korean news magazine, Sisa IN, and an opinion research organization, Hankook Research, to investigate the favorability of South Koreans towards North Korea, China, Japan, and the US. The results indicated that South Koreans exhibited the lowest level of favorability towards China, even lower than that towards Japan, and this trend had been on a downward trajectory for four consecutive years (Sisa IN 2021).

In international relations, conservatism is primarily reflected in the South Korean public’s identification with and support for the US. The 2022 South Korean presidential election has brought the issue of China to the forefront of political discourse. Both progressive and conservative factions adopted a challenging posture towards China as a political strategy. Some groups manipulated public opinion domestically while simultaneously seeking to gain favour with the US on the international stage. Conservatism has seen a resurgence in South Korea, with young politicians from the ruling or opposition parties openly denouncing China and a noticeable trend of growing diplomatic demand for South Korea to choose a side between China and the US. According to a survey conducted by the Pew Center in the spring of 2021, a significant majority of South Koreans, approximately 77%, held an unfavourable view of China. Moreover, the survey revealed that 75% of South Korean respondents believed their country should prioritize establishing closer economic ties with the US over China. In contrast, only 17% of the respondents supported China (Pew Research Center 2021).

On the contrary, South Korea has conventionally regarded the US–ROK alliance as the fundamental basis for national security and the most valuable strategic resource after the Korean War. The US is the primary foreign investment destination, second largest trade partner, and second most significant source of investment for South Korea. The increased collaboration between South Korea and the US is beneficial for bolstering South Korea’s industrial and security capabilities, securing its advantages in high-end industries, and alleviating the repercussions of upgrades to China’s industrial sector.

Finally, the impasse of South Korea’s policy towards North Korea was the direct cause of the shift in South Korea’s alliance strategy to reinforce the US–ROK alliance. After the US–DPRK summit in Vietnam, both countries failed to make any significant progress toward resolving the issue of denuclearization. Despite numerous attempts by South Korea to facilitate communication, their efforts have thus proven to be unsuccessful. In the latter years of the Moon Jae-in administration, progress has yet to be made on the nuclear issue. North Korea has abandoned direct communication with the US and South Korea, yet again leaving the Korean Peninsula at an impasse.

In June 2020, the Inter-Korean Liaison Office was demolished by North Korea, citing the South Korean government’s alleged support for the dissemination of anti-DPRK leaflets by conservative groups. Additionally, the 8th Congress of the Workers’ Party of Korea in January 2021 reaffirmed the strengthening of nuclear deterrence. In March 2021, North Korea publicly denounced the US–ROK joint command post-exercises and ‘2 + 2’ meetings between the foreign and defence ministers. North Korea demanded that the US and South Korea cease military exercises and abandon their hostile policies towards North Korea. It warned that failure to comply with these demands would result in a ‘significant security crisis’ for the US and South Korea (Hankyoreh 2021b). In 2021, North Korea recommenced missile test launches, which resulted in South Korea retaliating with military action, thereby escalating the ongoing military tensions between the two nations. On September 15th, after the launch of two short-range ballistic missiles, South Korea disclosed four strike weapons and released videos of each, including the Hyunmoo 4–4 SLBM. Following that, North Korea declared the successful test launch of the Hwasong-8 hypersonic missile. North Korea conducted more missile test launches in 2022, including short-range missiles and medium- and long-range ballistic missile tests, which had been suspended since November 2017. Kim Jong-un also paid a high-profile visit to the National Aerospace Development Administration and announced the future launch of additional military reconnaissance satellites (Yonhap News 2022c).

The current situation on the Korean Peninsula has again taken a turn for the worse, resulting in a divergence of perspectives between the US and South Korea concerning the North Korean issue. This suggests a reduced likelihood of the US endorsing South Korea’s position. The divergence between the two nations is primarily manifested in their disparate stances regarding the end-of-war declaration. During the meeting of the US, Japan, and South Korean trilateral national security advisors in April 2021, South Korea brought up the topic of drafting an end-of-war declaration on the Korean Peninsula with the US. However, the White House press statement did not disclose any details regarding the resumed dialogue between the US and North Korea, which suggests that the US remains committed to constraining North Korea and upholding sanctions.

Regarding the issue of human rights, Biden openly condemned North Korea’s human rights record based on shared values, and these sentiments were echoed in the communiqué published by the G7 foreign ministers’ meeting. In early October, National Security Office Director Suh Hoon of South Korea met with Jake Sullivan, National Security Advisor of the US, to discuss issuing the end-of-war declaration and terminating the state of war on the Korean Peninsula. However, the US remained non-committal to South Korea’s proposal, once again indicating the nuanced disparities between the US and South Korea on this issue.

Sullivan commented in a press briefing at the White House on the declaration that US–ROK discussions had been ‘very productive and constructive’ but that the two nations ‘may have somewhat different perspectives on the precise sequence, timing, or conditions for different steps.’ This marked the first public acknowledgement of the end-of-war declaration by the US. While South Korea and the US have been aligned in their approach to North Korea, there are specific differences in their perspectives (Yonhap News 2021b). It also implied that the US seeks to modify South Korea’s policy towards North Korea. This issue has been a subject of criticism by the Conservative party on the Moon administration, and the candidates have emphasized the US–ROK alliance significantly throughout the general election. Therefore, the South Korean government has to strengthen cooperation with the US.

5 Conclusion

During the US strategic contraction, the country urged its ally, South Korea, to take on more alliance obligations utilizing coercion, institutional constraints, interest alignment, and authority’s direction. However, these efforts have also raised concerns in South Korea about the potential for ‘entrapment’. In response, the alliance management strategy of South Korea shifted from seeking autonomy to reinforcing the alliance with the US. The rationale behind this shift can be attributed to several factors, including South Korea’s concerns about the possible decoupling from the United States, South Koreans’ growing unfavourable view of China, and the impasse in South Korea’s policy towards North Korea.

As a result of this adjustment, the positioning of the US–ROK alliance has been clarified, and cooperation has been further reinforced. First, the positioning and transformation trajectory of the US–ROK alliance has been reaffirmed. Since the end of the Cold War, the fundamental objective of adjusting or redefining the alliance has remained consistent: to augment South Korea’s position within the US Asia–Pacific alliance system and advance the regionalization and integration of the US–ROK alliance. As outlined in South Korea’s defence white paper, the ROK–US alliance has gone beyond a mere military alliance. It is evolving into a comprehensive strategic alliance on a bilateral, regional, and global scale, which is based on a shared commitment to liberal democracy and market economy. Second, the broad strategic alliance between the US and South Korea has been further solidified. Previously agreed-upon matters are now being put into practice, with South Korea gradually becoming an integral part of the US security collaboration network in the Asia–Pacific area.

Regarding the theoretical framework, in the context of a great power rivalry, a dominant state experiencing a relative decline in power may require increased support from a minor state to achieve its security objectives. This situation may incentivize the dominant state to request its allies take on a more significant share of costs in the alliance. In this scenario, the minor state begins to doubt the strategic reliability of the major power and fears being entrapped in alliance dilemmas due to the rivalry between major powers. As a result, the minor state develops a clear tendency to seek autonomy and aims to gain greater autonomy in future trade-offs. However, the case of South Korea serves as an example that demonstrates an asymmetric alliance, where the minor state may encounter challenges in maintaining an autonomy-seeking alliance strategy when confronted with an inherent security threat.