The Republic of Korea (ROK) and the United States (US) have been in a military alliance for almost seven decades since the two signed the Mutual Defense Treaty in 1953. Since then, the ROK and the US have maintained close security ties as client and patron states to deter the hostile actions of the Democratic People’s Republic of Korea (DPRK). Especially during the Cold War, the ROK-US alliance remained solid, acting as a defensive alliance and preventing the DPRK from committing violent actions that could destabilize the Korean Peninsula and East Asia. As the Cold War ended with the collapse of the Communist bloc, it seemed that the balance of power had tilted away from the DPRK and favored the ROK-US alliance. Some expected the isolated DPRK and its Kim regime to collapse at anytime.

Three decades have passed since the end of the Cold War. However, DPRK is still succeeding in resisting global pressure despite being sanctioned multiple times for its actions – conducting nuclear weapons tests and missile launches while initiating military clashes with the ROK. Instead, the DPRK’s act of provocation continues with no signs of ceasing. As shown in Table 1, DPRK’s provocations have continued almost every year since the beginning of the post-Cold War era (except in 2018).¹ Why does the ROK-US alliance fail to prevent the DPRK’s continued provocation?

A countless amount of literature has investigated the factors that affected the ROK-US alliance recently, such as the ROK’s economic development and democratization, ROK-US trade, defense cost-sharing issues, and the rise of China (DS Lee 2007; Heo 2008; H Kim and Heo 2016; D Kim and Heo 2018; Heo and Roehrig 2018; D Kim 2020). Other literature concentrates on the progressive and conservative ROK and the US administrations’ policies toward DPRK and how they have affected the ROK-US alliance (Joo 2006; SH Lee 2008; TH Kim 2013; YG Kim 2013; HR Park 2019). Besides these, other studies examine the strategies and approaches that the ROK and the US should adopt to address DPRK’s missiles and nuclear weapons (SW Cheon 2007, 2011; TH Kim 2008; CK Park 2010). The following sections will review some of these studies in more depth.

Regarding the DPRK, previous studies have examined the domestic sources of DPRK’s provocations, military policy, and development of nuclear weapons. Much of this literature stresses that military provocations are the DPRK regime’s expression of vulnerability and sense of insecurity (CM Lee 2007). The DPRK’s reasons for developing nuclear weapons are to gain deterrence capability against the ROK-US alliance (Roehrig 2016), to destabilize the region and gain bargaining leverage in exchange for its aggressive behaviors (Nah 2013), or to use as means to ensure the survival of the DPRK’s Kim family regime by strengthening its authority and legitimacy (Byman and Lind 2010; Ahn 2011; SY Park 2016). The DPRK has also sought to develop and gain nuclear weapons to secure its independence from China, its traditional ally that could also restrict its autonomy (MH Kim 2021a).

Previous literature provides insights into how ROK-US relations have evolved, which issues affect the relationship, and how the two states collaborate to deter the DPRK’s belligerent actions. Still, few have considered various factors simultaneously to provide a more comprehensive explanation of why the ROK-US alliance is falling short of conducting military retaliation to deter the DPRK’s further aggression. In addition, from the DPRK’s position, few studies examine the shift in the international and other countries’ domestic politics that formed a favorable condition for the DPRK to continue behaving aggressively or why the ROK and the US are not able to deter the DPRK’s aggression, gradually losing the advantage they held in terms of economic and military power since the 1990s.

Thus, this article aims to present a bigger picture of the situation on the Korean Peninsula by introducing international and domestic variables that weaken the ROK-US alliance’s ability to retaliate militarily and deter the DPRK’s aggression. The main factors that I will examine are 1) the DPRK’s possession of nuclear weapons, 2) the change in the ROK’s domestic politics, and 3) the strengthening of China-ROK economic ties (China factor I). Additionally, this article will discuss 4) the potential impact of the narrowing power gap between the US and China and its implications for the ROK-US Alliance (China factor II).

The first and the fourth factors negatively affect the ROK-US alliance’s strength against the DPRK because they restrict the alliance’s capability to retaliate and punish the DPRK for its provocations. In other words, the DPRK’s nuclear weapons could damage the alliance’s deterrence capability. It could also damage the alliance’s solidarity because the US might reduce its commitment to the ROK, especially since the DPRK’s nuclear weapons can now reach and threaten its territory. Besides, China’s rise could weaken the ROK-US alliance’s relative strength vis-à-vis the China-DPRK bloc since the DPRK’s protector is becoming more and more capable of deterring the alliance from using military means toward its client.

Meanwhile, the second and third factors hinder the alliances from preventing the DPRK’s provocations by negatively affecting the ROK’s willingness to cooperate with the US. In other words, the two states’ interests and threat perceptions regarding the DPRK could diverge further due to these two factors, deteriorating the alliance’s solidarity and cohesiveness.

Since this study is based on a qualitative research approach, rather than demonstrating that one factor has a more significant impact on the outcome than the others, I argue that the “combinations of causes” produce the expected outcome (Goertz and Mahoney 2012, 57). In other words, the four factors will be regarded as “causal packages or recipes” that generate the outcome (Goertz and Mahoney 2012, 57).²

The article will proceed as follows. The first section will review the theoretical frameworks that will act as a foundation of this research. The second section will analyze how DPRK’s possession of nuclear weapons has restricted the ROK-US alliance’s options to address the issue in its favor. The third section will discuss how a shift in the political orientation of the ROK’s governing party affects the dynamic of the ROK-US alliance. The fourth section will examine how the China-ROK economic ties, which continued to strengthen recently, impact the ROK-US relationship. Finally, the fifth section will discuss how the power dynamics between the US and China have changed throughout the recent decades and how that might affect the DPRK’s behaviors. The article will conclude by discussing the implications of these four factors on the future of ROK-US relations and their collaboration to deter the DPRK’s aggression.

First, an alliance is formed when the two (or more) states need to address a common external threat (Weitsman 2004). Second, an alliance could either have an offensive or defensive goal (while some alliances might pursue both goals) (Snyder 1997). Besides, an alliance could be either symmetric or asymmetric depending on whether the power gap between the two (or more) states is large or not. Particularly in an asymmetric alliance, a “patron-client” relationship is formed in which the superior state provides protection and support to the weaker state while the latter relinquishes a certain proportion of its autonomy in exchange (Shoemaker and Spanier 1984; HR Park 2019). In this alliance case, a patron protects and supports a client by providing extended deterrence, such as the nuclear umbrella. Still, extended deterrence should be backed by credibility, which should be followed by the three elements – discouraging the aggressor from attacking the client by sending signals that the patron has the capability to protect the client, possesses the resolve to protect its client, and that the cost of provocation would be high to the aggressor if it initiates one (Heo and Roehrig 2018, 27).

Meanwhile, as long as the allies share a common goal and the members are satisfied with the current status, the alliance will persist. Also, alliances are likely to survive when the members continue to view each other as credible, committed, and reliable partners (Walt 1997, 165).

However, within the alliance, the level of coordination and cooperation each side desires or demands could shift over time. First, when a client state’s economy develops rapidly while the aggressor’s economy stagnates or declines, the former might no longer perceive the latter as a threat (Heo and Roehrig 2014). In this case, the patron and client might need to reevaluate the alliancés status to determine their future goal since they no longer share a common threat perception. Besides, the rapid economic development of an alliance member could be followed by democratic transition, accompanied by leadership changes. With new elites in power, that state’s perception of national interest and the external threat could shift, weakening the alliance’s cohesion (Heo and Roehrig 2018, 41-44). Third, a member state’s rapid economic development could be accompanied by an increase in that state’s national pride, starting to demand adjustments in how the alliance operates – to form an equal and autonomous relationship with the stronger partner (DS Lee 2007). Fourth, while the client is always concerned about being abandoned by the patron, the chances of getting entrapped in the patron’s affairs are also something the client wants to avoid. Abandonment occurs when a state’s ally de-aligns with the former and realigns with the opponent or when the ally does not provide support when the former expects it (Snyder 1984, 466). On the other hand, entrapment occurs when a state gets involved in its ally’s conflict, which the former has no interest in getting dragged into (Snyder 1984, 467). Especially when the allies no longer share a common goal or the goals between them diverge, hesitating to assist the ally due to the fear of being entrapped could cause the alliance’s solidarity to deteriorate. Finally, the status of an alliance needs reevaluation when the states doubt each other’s credibility (Walt 1997, 160-161). For instance, when the aggressor can physically attack the patron’s territory, the latter might hesitate to continue and provide extended deterrence to the client. Since the cost of protecting and supporting the ally could now increase, the patron could reduce its commitment to the client, damaging its credibility. In this case, the client might pursue internal balancing rather than relying on external balancing, weakening the solidarity of the alliance.

Thus far, I reviewed and introduced literature discussing why alliances can be formed and sustained but require adjustments to their goals or the way they operate. Applying these explanations, in the following sections, I will examine why the ROK-US alliance’s strength and solidarity necessary to deter the DPRK’s provocations might be weakening.

The DPRK’s Nuclear Weapons

As briefly mentioned in the introduction section, there are various reasons why the DPRK has shown an attachment to developing nuclear weapons. The first explanation is that the DPRK is developing nuclear weapons for national security (CM Lee 2007). Since the DPRK cannot compete with the ROK and the US in terms of conventional weapons considering its economic weakness, possessing nuclear weapons would be the only way to guarantee its security against threats posed by the ROK-US alliance. The second explanation is that the development of nuclear weapons is associated with the Kim family’s intention to secure its authority and legitimacy within the DPRK (Byman and Lind 2010; Ahn 2011; SY Park 2016). The deteriorating economic conditions and famine, combined with the succession of power from Kim Il-sung to Kim Jong-il to Kim Jong-un, necessitated the Kim family to strengthen solidarity within the DPRK’s population. By developing and testing nuclear weapons, the Kim family intended to gain public support by demonstrating a solid resolve that it is resisting a great power such as the US. Besides this, the possession of nuclear weapons could symbolize a state’s modernity, boosting the people’s national pride. Thus, nuclear weapons could be used as an objective that strengthens the regime’s authority and legitimacy at the same time (MH Kim 2021a, 1492). According to the third explanation, the DPRK has developed nuclear weapons to use as a bargaining chip to extract economic assistance from adversaries such as the US (Nah 2013). The fourth explanation adopts the “madman theory” and views the DPRK as irrational (Roy 1994a).

The first DPRK nuclear crisis occurred in 1993-94 when DPRK prohibited the International Atomic Energy Agency (IAEA) from inspecting its suspicious nuclear facilities in Yongbyon. After refusing to comply, the DPRK withdrew from the nuclear non-proliferation treaty (NPT) in March 1993, increasing international tensions even further. In reaction, the US, under the Clinton administration, considered conducting an airstrike on the Yongbyon facility, a move that could have pushed the situation to the brink of the 2nd Korean War. Fortunately, the US and DPRK were able to reach an agreement through negotiations, which was possible due to former US President Jimmy Carter’s visit to Pyongyang, meeting with DPRK leader Kim Il Sung to hold talks. As a result, the US and the DPRK signed the Geneva Agreed Framework in October 1994, ending the nuclear crisis peacefully as the US promised economic assistance (i.e., building light-water nuclear reactors, which the ROK financed) in exchange for the DPRK freezing its nuclear program.

Still, the DPRK continued its nuclear development, causing the second nuclear crisis in 2002 when the US found through its intelligence that DPRK was developing a highly enriched uranium (HEU) program, which the DPRK also admitted. The Geneva Agreed Framework broke down while the DPRK declared its withdrawal from the NPT in 2003. The DPRK also continued to develop its nuclear program, enough to conduct the first nuclear test in October 2006.

During this period, although both the ROK and the US agreed that the DPRK should be denuclearized, there was a considerable gap in the two states’ approaches to achieving that shared goal. While the George W. Bush administration continued to adopt a hard-line policy toward the DPRK and its nuclear weapons – even considering economic sanctions or military means if necessary (Joo 2006, 71) – and a freeze of its nuclear program before providing any economic assistance in exchange, the ROK’s progressive Kim Dae-jung and Roh Moo-hyun administrations demonstrated pro-DPRK attitudes, advocating for a peaceful solution through engagement and cooperation with the DPRK (Joo 2006, 68). Still, the two progressive administrations’ pro-DPRK stance had little effect on restraining the DPRK from developing nuclear weapons (Joo 2006, 78-79).

However, besides the mismatch between the ROK’s and US’s approaches, which hindered any coordinated efforts from the alliance, another reason the ROK-US alliance was not able to prevent the DPRK from developing nuclear weapons was that, since the 9/11 attacks in 2001, the US’s primary focus had been fixed on the two wars in the Middle East – Afghanistan and Iraq. Thus, to the Bush administration, DPRK and the issue of its nuclear weapons – which was still considered to be in its early development stage – was not its priority (Joo 2006, 76).

During the era of Lee Myung-bak (2008-2013) and the Obama administration (2009-2017), the two countries again agreed to a “conditional/strict reciprocity” principle – that the DPRK abandoning its nuclear weapons would be the precondition for receiving economic aid and normalizing its relations with the US (YG Kim 2013, 192-193, 197). Specifically, during its tenure, the Obama administration adopted the strategy of ‘strategic patience’ in which the US would only act when the DPRK sincerely intended to abandon its nuclear program and return to negotiations (DS Kim 2016, 33). However, such a strategy caused a deadlock in DPRK-US relations as any type of official talks were suspended because the DPRK had no intention of giving up its nuclear weapons (DS Kim 2016, 41). Besides using the Obama administration’s patience as an opportunity, the DPRK took advantage of the US’s negligence and continued developing and upgrading its nuclear capability (DS Kim 2016, 41-43).

According to scholars, there are several reasons why the Obama administration opted for a strategic patience strategy. First, when Obama took office, the administration’s foreign policy priority was on the Middle East and pulling the US troops out of Iraq (Delury 2013). Second, believing that the DPRK was rational and that mutual nuclear deterrence was at work, the US did not consider the DPRK a severe threat to its national security (DS Kim 2016, 36). Third, the Obama administration expected the ROK to play a more significant role (DS Kim 2016, 37). At the same time, the administration feared the possibility of being entrapped in inter-Korean conflicts (Jackson 2019, 601-602). Fourth, the Obama administration had doubts about whether holding negotiations with the DPRK was a good idea considering its reputation as an unreliable state (DS Kim 2016, 38). Fifth, “collapsism,” the belief that the DPRK’s Kim regime would eventually collapse and its nuclear program would fall with it, prevailed within the administration (Jackson 2019, 608-612).

Regardless of why the Obama administration adopted the strategy of strategic patience during its tenure, the DPRK conducted its second nuclear test in May 2009 and eventually proclaimed itself a nuclear state by amending its constitution in 2012. Then, the DPRK conducted its third, fourth, and fifth nuclear tests in February 2013, January 2016, and September 2016, respectively. (The DPRK conducted its sixth nuclear test in September 2017, during the Donald Trump presidency.)

Since the DPRK emerged as a de facto nuclear state (MH Kim 2020), its nuclear capability has worked as a game-changer that shifts the power dynamics on the Korean Peninsula. As the ROK is a non-nuclear state, its advantage in conventional weapons will be offset by the DPRK’s nuclear weapons, adding security pressure on the ROK (CK Park 2010, 502). Also, with its nuclear weapons, the DPRK now possesses counter-deterrence capability against ROK-US aggression, enabling the DPRK to continue its military provocations without fear of retaliation. Besides, the DPRK going nuclear could also change the “regional balance of power” as the DPRK-China alliance is composed of two nuclear states while the ROK-US alliance is not, tilting the power balance in the former’s favor (MH Kim 2021a, 1496).

Also, a military strike on DPRK’s nuclear facilities is no longer an option since the DPRK has become a nuclear state and has already developed long-range missiles that could reach US territory. When the aggressor is capable of not only threatening the client but the patron as well, the chances of the patron seeking decoupling from the alliance, rather than continuing to provide extended deterrence, increases (Heo and Roehrig 2018, 27-28). In such a context, the US might hesitate to provide a nuclear umbrella for the ROK, considering the possibility that the DPRK could retaliate using nuclear weapons or missiles that could reach its mainland (HR Park 2019, 460, 468; MH Kim 2021a, 1497). Then, the ROK might fear that the chances of abandonment by the US will increase. While the former is unlikely to occur, the ROK might believe that the US might make the latter choice. When the US does not provide extended deterrence, the ROK has no other option but to seek internal balancing against the DPRK’s nuclear weapons – developing its own nuclear weapons. There are already individuals and groups arguing that the ROK should go nuclear (Ahn and Cho 2014; D Kim 2020). However, the US will strongly oppose such a choice by the ROK because the US would not want to see nuclear weapons proliferating in East Asia. Such a gap regarding whether the ROK should possess nuclear weapons will become a source of friction between the two allies.

In short, DPRK “no longer poses a nonproliferation problem; it poses a nuclear deterrence problem” (Sagan 2017, 72). In other words, the ROK and the US cannot deny that the DPRK has succeeded in developing and possessing nuclear weapons, compromising the ROK-US alliance’s capability to deter the DPRK’s future aggression further.

A Shift in the Political Orientation of the ROK’s Governing Party

The ROK and the US have been military allies for more than a half-century. Throughout the decades, despite occasional conflicts and disagreements, the ROK and the US have regarded the DPRK as a threat to peace on the Korean Peninsula, agreeing to maintain a close alliance relationship. During the Cold War era, pro-American sentiments were the mainstream ideology within ROK society due to the authoritarian administrations’ pro-US and anti-DPRK stances (Oh and Arrington 2007, 336).

Meanwhile, a democratic transition occurred in the ROK during the 1980s, which resulted in the June 1987 democratic reform when the authoritarian Chun Doo-hwan administration agreed to hold a free and direct presidential election. Afterward, in 1993, Kim Young-sam became the first civilian leader in 33 years. (His predecessor Roh Tae-woo was also elected through a free and direct election but had a military background like the authoritarian presidents before him.) After Kim Young-sam, in December 1997, Kim Dae-jung became the first presidential candidate from the opposition (progressive) party to win the presidential election, which was a significant event that symbolized the development and consolidation of democracy in the ROK. Furthermore, democratization in the ROK was followed by administrations in the 1990s allowing people to express their views more freely. As a result, negative attitudes toward the US, which were suppressed during the authoritarian administrations, gradually became more widely accepted and demonstrated in public.

Meanwhile, democratization and change in the governing party allowed the rise of the new elites, resulting in a blending of democracy and nationalism (Chung 2003). In other words, in the ROK, progressives were also nationalists who led the democratization movement in the past.

Such a rise in nationalism and democratization had significant repercussions within the ROK. Specifically, the rise of nationalism led to the emphasis on maintaining a close relationship with the DPRK, which is regarded as historically sharing the same national identity as the ROK. The Kim Young-sam and Clinton administrations showed coordinated efforts to solve the first DPRK nuclear crisis in 1993-1994. However, when Kim Dae-jung and Roh Moo-hyun became the presidents of progressive administrations, the two states’ relations started to deteriorate.

One of the main reasons for increased friction between the ROK and the US was the progressive administrations’ different approaches to the US and DPRK compared to conservatives. While conservatives (the group that governed ROK throughout the Cold War era and until 1997) are mainly pro-US and anti-DPRK, progressives are anti-US and pro-DPRK. As a result, diverging attitudes toward the DPRK and its nuclear weapons led to friction in the ROK-US relations during the progressive administration era, compromising the alliance’s solidarity.

Specifically, since the progressive period of the Kim Dae-jung administration, there has been a de-emphasis on DPRK threats and an emphasis on the need for solidarity with the DPRK (DS Lee 2007, 481). In other words, there were movements to de-securitize the North Korean threat during the era of the Kim Dae-jung administration, which lasted throughout the Roh Moo-hyun administration (SH Kim and G Lee 2011). There has also been a change in the discourse that the DPRK’s military is relatively weak compared to the ROK’s and that the DPRK cannot pose a threat to the ROK. Instead, according to progressives (nationalists who also support democratization movements), the DPRK is a neighbor that should be embraced. Thus, progressives argued that the ROK’s foreign policy should focus on easing the DPRK’s sense of fear because the DPRK’s nuclear weapons are intended for self-defense, not for offense.

As a result, believing that the DPRK’s intention to develop nuclear weapons was for the survival of its regime, not for use against the ROK or to threaten peace on the Korean Peninsula (Cheon 2007, 10), the ROK’s progressive administrations refused to take a tough stance. Instead, Kim Dae-jung and Roh Moo-hyun adopted engagement policies toward the DPRK (the “Sunshine Policy” and “Peace and Prosperity Policy,” respectively). Specifically, Roh once mentioned that he did not view the DPRK’s nuclear weapons as a threat to the ROK (Reuters 2007). Roh also believed that the DPRK would abandon its nuclear weapons in exchange for economic assistance and rewards. Thus, progressive administrations believed that the DPRK would give up its nuclear weapons when it secures economic assistance and regime survival, especially from the US.

However, regarding the DPRK, the conservative Bush administration continued to view its regime with suspicion, refusing to believe that the DPRK would discard its nuclear weapons in exchange for economic aid. Instead, the US claimed that the DPRK should discard its nuclear weapons first before it could negotiate terms with the US. Thus, not only did the Bush administration not support Kim Dae-jung’s Sunshine Policy, but it called the DPRK part of the “Axis of Evil,” along with Iran and Iraq, in 2002 (DS Lee 2007, 480). Still, nationalists within the ROK accused the US of exaggerating the threat posed by the DPRK. In May 2003, Presidents Roh and Bush agreed to the principle of “complete, verifiable, and irreversible dismantlement (CVID)” regarding the DPRK’s nuclear weapons. Still, while the ROK argued that the nuclear crisis should be solved by peaceful, diplomatic means, the US considered a military option viable if DPRK continued to refuse to dismantle its nuclear weapons. In short, the Bush administration was uncomfortable with the Roh administration’s stance toward the DPRK.

In addition, changes in ROK leadership and the rise of nationalists, which were possible due to the earlier democratization, resulted in the weakening of the ROK-US alliance because Koreans started demanding more autonomy from the US, wanting to form an equal relationship with the US. For instance, Kim Dae-jung and Roh Moo-hyun's progressive administrations had diverging interests with the conservative Bush administration (2001-2008) regarding the relocation of United States Forces Korea (USFK), revision of the ROK-US Status of Forces Agreement (SOFA), and transfer timing of the wartime Operational Control Authority (OPCON) to the ROK.

In short, for an alliance to persist, members sharing a common threat perception is crucial (Heo and Roehrig 2018, 37). However, economic development, increased national pride, and a transition to democracy, accompanied by progressives gaining control of the ROK government, caused a divergence in threat perception between the ROK and the US.

When the conservative leader Lee Myung-bak succeeded Roh, the ROK’s attitude toward the DPRK turned negative compared to the previous ten years of the progressive administration period. Conservative leaders have tried to maintain a close relationship with the US because they see the presence of the USFK in the ROK as essential in deterring the DPRK’s hostile actions and guaranteeing the safety of the ROK. For instance, in response to the sinking of the Cheonan , the ROK and the US conducted a joint military exercise in the Yellow (West) Sea in July 2010 to demonstrate their resolve that they would not tolerate the DPRK’s further aggression. The sinking of the Cheonan aggravated China- ROK relations while reinforcing ROK-US relations (Ku 2015, 263). Furthermore, the conservative president Park Geun-hye, who succeeded Lee, decided to join the THAAD system and allow the US to install the system within the ROK’s territory, further strengthening the ROK-US alliance.

However, following the impeachment of President Park Geun-hye, the progressives regained power under the presidency of Moon Jae-in. Like his progressive predecessors, Moon also implemented pro-DPRK policies while actively trying to mediate a series of summits between the US and DPRK leaders. The first summit meeting between US President Donald Trump and DPRK Chairman Kim Jong-un was held on 12 June 2018 in Singapore. However, the second summit meeting held from 27-28 February 2019 in Hanoi, Vietnam, collapsed. Although Moon continued to persuade the US to normalize its relationship with the DPRK and proposed that the two sides sign the “end-of-war declaration,” he failed to achieve the goal during his tenure as the dialogue between the US and DPRK leaders was suspended in 2019.

In short, since 1998, when the progressive Kim Dae-jung became the ROK president, progressives governed the ROK for approximately 15 years (1998-2008 and 2017-2022) in total, while conservatives were in power for approximately nine years (2008-2017). As the relative share of the period when progressives are holding power increases compared to the decades before 1998 when conservatives firmly governed the ROK, the period of friction between the ROK and the US will also increase.

Still, the ROK’s progressives and conservatives are both committed to the ROK-US alliance. Although the relationship was fraught with friction, progressive presidents Kim Dae-jung and Roh Moo-hyun never considered devaluing the alliance (Bae 2010; JC Kim 2015, 49). For instance, Roh also acknowledged that maintaining the ROK-US alliance is essential in deterring threats posed by the DPRK (Yoo 2012, 336). Thus, the Roh administration concluded ROK-US Free Trade Agreement (FTA) negotiations during its tenure. The ROK-US FTA is expected to strengthen the economic ties between the two states, which will also prevent the relations from deteriorating, having security implications as well (Heo 2008).

Still, the gap in their views toward the DPRK and its nuclear weapons has been a source of friction that prevents the ROK and the US from strengthening cooperation (JC Kim 2015, 49; HR Park 2019, 469). The gap in the views – particularly between the US and progressive ROK administrations – toward the DPRK will continue to be a major source of conflict that will prevent the ROK and the US from showing unified and coordinated efforts in addressing the DPRK’s provocations.

China Factor (I): ROK’s Increasing Economic Dependence on China

While the ROK and the US enjoyed a solid alliance relationship during the Cold War era, change in the global landscape – the end of the Cold War – started to affect the relations between the two states. In August 1992, China and the ROK normalized and established diplomatic relations severed during the Cold War era. Since then, the China factor continued to intervene between the ROK and the US.

Throughout the decades, economic ties between China and the ROK have strengthened significantly. Figure 1 shows how ROK-US trade and China-ROK trade as a proportion of the ROK’s total commodity trade have changed from 1990 to 2020 based on United Nations Comtrade Database data. Total commodity trade between the ROK and China has spiked from US\$2.85 billion in 1990 to US\$241.45 billion in 2020, increasing 84.7 times during the last three decades. Such a dramatic increase in goods trade had a significant impact on the ROK’s economy, which bilateral commodity trade (export and import) with China accounted for approximately 24.6% of its total commodity trade in 2020. In 1990, bilateral commodity trade with China accounted for approximately 2.11% of the ROK’s total trade. Instead, in 1990, 26.9% of the ROK’s bilateral trade was conducted with the US. However, the figure fell to 9.6% in 2012 while it bounced back to 13.48% in 2020. In short, the share of ROK-US bilateral trade on the ROK’s total commodity trade decreased 50% during the last three decades. China surpassed the US during this period and became the ROK’s largest trade partner in 2004 (Ye 2016, 101).

However, bilateral trade with the ROK accounted for 5.1% of China’s total commodity trade in 2020, slightly increasing from 3.9% in 1990. Since approximately a quarter of ROK’s commodity trade is conducted with China, as shown above, while merely one-twentieth of China’s commodity trade is conducted with ROK, such a result indicates that the ROK and China are in an asymmetrical trade relationship in which the ROK is economically more dependent on China than vice versa. Also, from 1990 to 2020, China’s impact on the ROK’s economy became more significant than that of the US.

When economic ties with China became more and more critical to the ROK’s economy and its growth, ROK administrations have shown efforts to maintain positive relations with China. For instance, while frictions with the US increased, the progressive Kim Dae-jung (1998-2003) and Roh Moo-hyun (2003-2008) administrations sought a cooperative relationship with China, sequentially upgrading the relationship from a “friendly cooperative relationship” in 1992 to a “cooperative partnership” in 1998 to a “comprehensive cooperative relationship” in 2003 (MH Kim 2016b, 713). For progressive administrations, China’s cooperation – acting as a mediator of peace – was essential to peacefully solving the DPRK’s nuclear weapons crisis (JC Kim 2015, 43). For example, China acted as a broker of the Six-Party Talks from 2003 until 2007 (Horowitz and Ye 2006).

Even conservative administrations that are regarded as having a pro-US stance did not cease to pursue close ties with China. While the bilateral relationship was upgraded to a “strategic cooperative partnership” in 2008, the Lee Myung-bak (2008-2013) administration also initiated Free Trade Agreement (FTA) negotiations with China in May 2012, intending to strengthen bilateral economicties further. The subsequent conservative Park Geun-hye administration (2013-2017) continued seeking friendly ties with China. For instance, in September 2015, Park attended the military parade commemorating the 70th anniversary of China’s victory and Japan’s surrender in World War II. Also, in March 2015, the ROK joined the China-led Asian Infrastructure Investment Bank (AIIB) as a founding member even though the US urged the ROK to reconsider its decision. Furthermore, during Park's presidency, the two sides signed the China-ROK FTA in June 2015, which entered into force in December 2015.

When the progressive Moon Jae-in (2017-2022) came into power, he adopted what was viewed as a “pro-China” policy (JW Kim 2021; SH Lee 2021; MH Kim 2021b). The Moon administration believed China’s cooperation was essential in addressing the DPRK’s nuclear weapons crisis. Besides this, in November 2020, the ROK decided to join the China-led Regional Comprehensive Economic Partnership (RCEP) trade bloc, which excludes the US. (The trade deal came into effect in February 2022 in ROK).

However, the ROK’s relationship with China is also fraught with conflict. When the DPRK allegedly attacked and sank the ROK corvette Cheonan and bombarded Yeonpyeong island in 2010, unlike after the DPRK’s nuclear weapons and missile tests mentioned above, China refused to condemn the DPRK for its act of aggression toward the ROK. Such a decision by China, refusing to join the ROK and the US in condemning and sanctioning the DPRK, disappointed the ROK amid the blooming trade relations, resulting in the strengthening of the ROK-US alliance. Thus, the ROK and the US conducted joint military exercises in July and November 2010 to display force to the DPRK. However, regarding the ROK-US joint military exercises, China expressed concerns and urged the allies to stop the event. China expressed discomfort regarding the ROK-US joint military exercise being conducted and the US fleet operating near its eastern coast – the Yellow, Korea’s West Sea – claiming that such actions threaten regional stability as well as China’s national security.

Furthermore, when the ROK started to discuss with the US whether to deploy the Terminal High Altitude Area Defense (THAAD) to defend against the DPRK’s missiles, China strongly opposed the ROK’s move, warning that the deployment would seriously damage China-ROK relations. Although the ROK and the US responded by arguing that THAAD is an anti-missile defense system that will be used solely to deter the DPRK’s missile provocations, China expressed discomfort that THAAD’s radar would be used to survey China’s territory and locate its strategic missiles (Kim and Blanchard 2016; Buckley 2017). The underlying argument for China’s opposition to THAAD being installed in the ROK is that THAAD’s radar capability far exceeds what is necessary merely for the ROK’s defense (Consulate-General of the People’s Republic of China in Los Angeles. 2016). Thus, when the ROK finally decided to deploy THAAD, in July 2016, during the conservative Park Geun-hye administration, China strongly protested and imposed economic sanctions on exports from the ROK in retaliation.

The ROK regards the THAAD incident as an event demonstrating how asymmetric trade relations – the ROK’s economy relies heavily on export to China – could be exploited in China’s favor. As China decided to restrict the ROK’s exports to China, the ROK’s economy was exposed to sensitivity and vulnerability as export firms, and tourism industries were hit hard.

Although China no longer provides unconditional support to DPRK, it is also unlikely for China to strengthen its relations with the ROK at the expense of its Cold War-era ally, the DPRK (MH Kim 2016c, 73). China continues to act as an “external lifeline and a major source of economic exchange” for the DPRK (Snyder 2009, III). One of the main reasons for China’s behavior is to prevent a situation in which the DPRK collapses and China has to share a border with the ROK-US alliance. Thus, it is in China’s national interest to assist the DPRK’s survival so that it remains a buffer zone between China and the ROK-US alliance (Grinter 2008, 297-298; Song 2011, 1137-1139). Besides, China fears that a collapse of the DPRK regime could lead to an influx of DPRK refugees into China’s territory (Song 2011, 1137). Thus, even though China occasionally denounces the DPRK and agrees with others to impose sanctions on it, China continues to act as its protector, not abandoning its traditional ally. If such a situation continues, denuclearizing the DPRK through sanctions – one of the ROK-US alliance’s aims – would be a challenging goal (Song and SK Lee 2016, 28).

Besides, even though the ROK maintains a strong alliance relationship with the US, the rise of China and increased economic interdependence could affect the ROK’s stance in East Asia. South Koreans' negative sentiments toward China had increased, particularly after the THAAD incident when China retaliated economically (D Kim 2021). Still, the ROK has not shown signs of firmly balancing against China, despite China’s economic and military rise. One of the reasons for the absence of the ROK’s balancing behavior toward China, other than its military alliance relationship with the US, is because of a considerable amount of economic benefits that the ROK reaps from trade with China and because the ROK regards China’s cooperation as essential to containing the DPRK and solving the nuclear problem peacefully (MH Kim 2016b, 720-722). Also, the ROK regards China’s support as essential to prevent the DPRK’s provocations while pursuing a peaceful Korean unification (MH Kim 2018, 615-617).

Nor is the ROK likely to reduce its security ties with the US because of its economic ties with China (MH Kim 2016c, 74). However, considering that China has been the ROK’s largest trade partner for more than a decade now and that the ROK is in beneficial but vulnerable, asymmetrical trade relations with China, combined with the possibility that China could exploit the situation to its advantage, the ROK’s strategy of hedging between the US and China could continue for the time being (MH Kim 2016c, 75). While the US is a crucial security partner, China is the ROK’s most significant trade partner. Such a hedging behavior could reduce the US’s relative influence on the ROK, compromising the ROK-US alliance’s ability to deter the DPRK’s aggression. Thus, to prevent the ROK from leaning toward China instead, the US should show a firm commitment to the alliance while maintaining preponderance in the region (JC Kim 2015, 47-52).

An Additional China Factor (II): The Potential Impact of China’s Rise on the DPRK’s Provocations and its Implications for the ROK-US Alliance

Meanwhile, the power dynamics between the US and China have continued to shift throughout the decades. With its economic reform and adoption of an open-door policy in 1978, China’s economy started to grow rapidly. Especially since it joined the World Trade Organization (WTO) in 2001, China’s trade has increased exponentially, becoming the largest goods trading country – the largest in exports and the second largest in imports – surpassing the US in the mid-2010s. As a result, according to the World Bank data, the size of China’s nominal gross domestic product grew to be 40.8 times larger between 1990 and 2020.³ In terms of GDP measured in purchasing power parity (PPP), the size of China’s economy grew 21.79 times between 1990 and 2020.⁴ During the same period, the size of the US’s economy merely increased by 3.51 times, both in terms of nominal and PPP GDP. Examining the data from a different angle, as shown in Figure 2, while the US economy was 16.52 times larger than China’s in 1990, it was only 1.42 times larger in 2020 in terms of nominal GDP. In terms of PPP, while the US economy was 5.35 times larger than China’s in 1990, China surpassed the US in 2017, as its economy became 1.16 times larger than the US’s.

However, only employing GDP to measure states’ national capability fails to consider other aspects of power, such as military size or population. Thus, we need to compare the national capabilities of the US and China using a more sophisticated composite measure – the Composite Index of National Capability (CINC) score provided by the National Material Capabilities (NMC) Data Version 6.0 of the Correlates of War Project (n.d.). A state’s CINC score for a given year is computed using six variables – military personnel, military expenditures, total population, urban population, iron and steel production, and primary energy consumption. Using various variables allows the researchers to measure a state’s national capabilities from demographic and military dimensions besides the economy.

Measuring national capability using the CINC score shows a different result than when we measured it using only different versions of GDP. Figure 3 shows that China’s national capability overtook the US in 1995, and the gap has continued to increase during the 21st century. Specifically, the US’s CINC score decreased from 0.141 to 0.133 from 1990 to 2016, while China’s score doubled from 0.112 to 0.231 during the same period. Meanwhile, the ROK’s CINC score increased from 0.018 to 0.023, while the DPRK’s score stagnated between 0.012 and 0.013 during the same period. In other words, there has been a divergence in national capabilities between the two Koreas.

Figure 4 shows how the combined national material capabilities of the ROK-US and China-DPRK alliances, based on CINC data, have shifted between 1990 and 2016. While the ROK-US combined national material capabilities changed little during the period (CINC scores ranged between 0.15 and 0.18), China-DPRK’s combined capabilities doubled from 0.124 in 1990 to 0.244 in 2016. Specifically, beginning in 2004, the two blocs’ material capabilities started to diverge in favor of China-DPRK.

According to power transition theorists, the two states entered a parity situation when the rising state’s power reached 80 percent but did not exceed 120 percent of the declining states (Rauch 2017, 646). Following such a standard, China and the US started a parity period in 2010, when national capabilities were measured through the PPP of GDP. On the other hand, in terms of nominal GDP, China is yet to reach parity with the US as of 2020. Meanwhile, when we measure national capabilities using CINC scores, the US and China were in parity until 2007. However, since 1995, China, not the US, has had a larger national capability. Then, between 2008 and 2020, the US’s national capability fell below 80% of China’s, putting them outside the parity range. Now China is widening its material capability gap with the US, consolidating its status as the world’s leading great power.

Whether China has surpassed the US in terms of national capability depends on which data we use. Still, data shows us that China’s national capability is growing rapidly while the US is stagnating (or declining). Thus, either the power gap between the US and China is narrowing, or the power balance is tilting in China’s favor.

According to the balance of power theory, wars become less likely and stability is achieved when power parity is met, especially among great powers (Waltz 1979). One of the reasons the likelihood of war decreases when great powers’ strength becomes balanced is that the risk of initiating wars increases while chances of victory decrease (Lemke and Kugler 1996).

However, rather than automatically assuming that the balance of power brings stability, we need to consider whether a state is satisfied with the status quo or not in addition to its national capability. Thus, according to the power transition theory, great power wars are likely to occur between a dissatisfied rising state and an incumbent but the declining dominant state (Organski 1968; Organski and Kugler 1980; Gilpin 1981).

Is China a dissatisfied rising state then? While there are scholars arguing that China is not a revisionist state (Fravel 2008; Johnston 2003; Kang 2005; Shambaugh 2005; Scott and Wilkinson 2013), other scholars advocate the “China threat” argument (Christensen 2006, 2015; Mearsheimer 2006, 2010; Roy 1994b, 1996, 2005), suggesting or introducing evidence and backup theories explaining why China’s rise will destabilize the existing regional and global order, attempting to dethrone the US from its hegemonic status. In this case, the US and China are likely to fall into “Thucydides’s Trap,” which increases the chances of military clashes between the two great powers (Allison 2017).

Violent conflict, such as wars, would still be unlikely despite the shift in power dynamics between the US and China (Grieco 2014). However, there are signs that strategic competition and rivalry between the two great powers are increasing recently over fields such as technology and economy or regions such as the South China Sea, Taiwan Strait, and the Korean Peninsula (MH Kim 2019; Zhao 2019; Wu 2020).

Due to China’s rapid rise and a decline in the US’s influence and supremacy in the region, the US is no longer in a position to unilaterally wield its dominance in East Asia (Layne 2012). While the denuclearization of the DPRK through military means might have been possible in the 1990s when the US wielded global political, economic, and military supremacy, its preponderance has waned in the first two decades of the 21st century. Now, China, which has risen and acquired the US’s regional competitor status, will not standby and agree to military operations conducted within its bordering state.

Such a change in the regional context could affect the DPRK’s actions. China and the DPRK have conflicting interests regarding whether the DPRK should continue developing nuclear weapons, an action that provokes its neighbors, and whether it should implement Chinese-style economic reform and open its economy (MH Kim 2017). Still, the DPRK strongly believes that China could not afford to let its regime collapse (MH Kim 2016a). China has little option but to embrace the DPRK to a certain extent despite the frequent provocation of its neighbors. On the other hand, the DPRK is willing to exploit such a situation – that China has to continue acting as its protector – committing more bold actions instead of refraining from them (MH Kim 2016a, 995).

Besides, other than the fact that the DPRK has to remain an important strategic ally to China, China’s rapid rise and shift in power dynamics between China and the US are also likely to embolden the DPRK. The supremacy of the US vis-à-vis China, in terms of national capability, might have brought a sense of security to the ROK in the early decades of the post-Cold War era. However, China’s rise and the US’s decline are leading to a potential shift in the power balance, which could now increase the DPRK’s assertiveness since it will start to believe that China is capable of providing protection against the potential military attack by the US. Thus, rather than balancing against China, the long history of the relationship suggests that the DPRK might decide to bandwagon with China, the rising great power in the region. We certainly need more evidence to tell whether this scenario will actually occur in reality. Still, in short, the rise of China has the potential to negatively affect the ROK-US alliance’s ability to deter and contain the DPRK from conducting hostile actions.

Throughout the Cold War and the first 30 years of the post-Cold War era, the ROK-US alliance, despite having inner frictions occasionally, showed coordinated efforts to deter the DPRK from conducting belligerent actions that hinder peace on the Korean Peninsula and in East Asia. However, although the two states possess overwhelmingly superior economic and military material capabilities, the DPRK continues to conduct military provocations that threaten the security of the ROK and even the US.

In this context, this article aimed to provide a comprehensive account of why the ROK-US alliance is failing to deter the DPRK’s belligerent actions, such as initiating military attacks on the ROK and testing missiles and nuclear weapons. There are three simultaneously working international and domestic variables and one potentially acting variable that are changing the international environment, forming a favorable condition for the DPRK to continue its bellicose actions.

First, as the DPRK became a de facto nuclear state, the superiority the ROK and the US enjoyed in terms of conventional weapons no longer poses a threat to the DPRK. Since it has now obtained the deterrence capability against US nuclear weapons, the DPRK can perform aggressive actions without considering the consequences. Second, the political orientation of the ROK administration shifting from a constant to a variable – due to the democratization of the ROK – increased the chances of pro-DPRK progressives governing the ROK. As in the past, such a pro-DPRK position could increase frictions with the US, which usually adopts hardline policies against the DPRK, affecting the solidarity of the ROK-US alliance. Third, increased economic ties between China and the ROK in the post-Cold War era has the potential to create a schism in the ROK-US alliance. The China-ROK trade’s positive influence on the ROK’s economy could shift the ROK’s national interest while empowering China to wield political and economic influence over the ROK. In this context, rather than continuing to strengthen its alliance with the US, the ROK could opt for a hedging strategy between the US and China, depending on the situation and its national interest. Fourth, China's rise and the US's decline are shifting the power balance in favor of the China-DPRK bloc. Despite occasional friction, since its sole protector is gaining power and becoming more and more capable of challenging the US’s supremacy in the region, the DPRK could exploit the situation to its advantage, bandwagoning and continuing to provoke the ROK and the US with little concern for retaliation.

Such shifts in international and domestic variables surrounding the Korean Peninsula imply that the ROK-US alliance needs to perceive the change in dynamics and make proper adjustments to its DPRK policy. The US should find ways to maintain its primacy and competitiveness vis-à-vis China while reassuring the ROK that it will surely provide a nuclear umbrella. Otherwise, both the ROK and the US should explore ways to persuade China to pressure the DPRK to cease its aggression because China also shares common goals with the two states – regional stability and denuclearization of the DPRK. Finally, the ROK and the US should find approaches toward DPRK that the two states could agree on even when progressives are governing the ROK. Although it would be arduous to achieve these goals, the ROK and the US will be able to deter the DPRK’s further attempts to hinder peace once they succeed.

¹ In this study, provocations will refer to the violent actions initiated by the DPRK, excluding non-violent verbal actions aimed toward the ROK. As shown in Table 1, an act of provocation by the DPRK includes various violent activities such as, but not limited to, missile launch, infiltration and incursion, exchange of fire, (maritime or ground) territorial provocations, naval campaigns, and nuclear tests.

² Each factor’s effect on the outcome – reducing the strength and solidarity of the ROK-US alliance against the DPRK’s provocations – is not mutually exclusive. In reality, the four factors interact, overlap, and affect one another to a certain extent to produce the outcome. In other words, the boundaries between and among the factors might be indistinguishable in the real world. Still, for the sake of the explanation, I tried to classify the variables that lead to the outcome into four factors.

³ Calculated by the author. World Bank. (n.d). “GDP (current US\$).” Accessed at https://data.worldbank.org/indicator/NY.GDP.MKTP.CD?view=chart (April 1, 2022).

⁴ Calculated by the author. World Bank. (n.d.) “GDP, PPP (current international \$).” Accessed at https://data.worldbank.org/indicator/NY.GDP.MKTP.PP.CD?view=chart (April 1, 2022).