Kim’s Nukes, Yoon’s Qualms: Strengthening the US Nuclear Umbrella over South Korea

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  • By Dr. Adam B. Lowther


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Since North Korea’s first nuclear test in 2006, its rapid expansion of nuclear weapons and missiles has raised doubts in South Korea about US extended deterrence commitments. In 2023, President Yoon Suk-yeol opened discussion of an independent South Korean nuclear arsenal. This article examines South Korean perspectives and support for nuclear weapons through expert interviews and polling data analysis. It finds enduring fears of US abandonment drive South Korean interest in indigenous capabilities or a return of US nuclear weapons. Experts emphasize the need to improve South Korean understanding of nuclear strategy and assurance policies. Recommendations include strengthening the US–ROK Nuclear Consultative Group, increasing strategic asset deployments and exercises, enhancing information sharing on nuclear planning, and expanding Korean involvement in nuclear consultations and training. Given President Yoon’s concerns, concrete assurance efforts are critical to preventing a collapse of the global nonproliferation regime and a new nuclear arms race in Northeast Asia.



On 11 January 2023, South Korean President Yoon Suk-yeol announced that North Korea’s continued nuclear expansion could push the Republic of Korea (ROK) to pursue an indigenous nuclear weapons program.[1] At the time of Yoon’s statement, American credibility had diminished due to the United States’ failure to deter the Democratic People’s Republic of Korea (DPRK) from developing nuclear weapons and advanced ballistic missiles.[2] Former President Donald Trump’s handling of the Korean Peninsula also played a significant role in garnering popular support among South Koreans for an indigenous nuclear weapons program, with 71 percent expressing approval in recent public opinion polls.[3] Despite South Korea’s conventional superiority over North Korea, the DPRK’s possession of nuclear weapons raised concerns among South Koreans.[4]

In the days and weeks following President Yoon’s announcement, think tanks in Washington, DC, extensively discussed the gravity of Yoon’s remarks and their potential implications for the United States and the alliance.[5] The Biden administration promptly responded with an invitation for President Yoon to visit the White House.[6] In the weeks leading up to Yoon’s visit, the administration formulated a plan aimed at bolstering American assurance of the ROK and dissuading Yoon from pursuing an independent nuclear arsenal.

During President Yoon’s visit to the United States from 24 to 29 April, he dedicated 26 April to meetings with President Joe Biden at the White House.[7] In addition to commemorating the seventieth anniversary of the ROK–US alliance, the visit served as an opportunity to outline their strategy for enhanced cooperation. Officially known as the “Washington Declaration,” this statement focused on eight lines of effort.[8]

First, the United States and South Korea created the Nuclear Consultative Group (NCG) as a means for improving cooperation on matters of deterrence concerning North Korea.[9] This group will bring senior defense officials together to discuss nuclear strategy. The creation of the NCG received positive feedback, although some in Korea mistakenly equated it with the to the North Atlantic Treaty Organization’s (NATO) Nuclear Planning Group.

Second, the ROK reaffirmed its commitment to the Nuclear Non-proliferation Treaty (NPT) as the cornerstone of international nuclear nonproliferation and peaceful use. For the United States, the ROK’s agreement with this stance held paramount significance. A treaty ally pursuing nuclear weapons would erode American credibility.

Third, the United States pledged to increase the presence of strategic assets in and around South Korea, including additional exercises. The deployment of nuclear-capable bombers and ballistic missile submarines to Korea is perceived as a means to reassure South Korea and deter North Korea.

Fourth, both nations agreed to more effectively integrate South Korea’s strategic capabilities into the alliance’s combined force structure, thereby facilitating joint planning and execution. The ROK is establishing its own “Strategic Command” explicitly tasked with overseeing the nation’s conventional strategic weapons.[10]

Fifth, the United States will incorporate ROK military personnel into training courses and educational programs aimed at expanding their comprehension of nuclear issues and operations. This step is crucial given the limited understanding of strategic deterrence within the Ministry of National Defense, the military, and the broader foreign policy establishment.

Sixth, the United States and ROK will conduct intergovernmental and interagency simulations and separate tabletop exercises with US Strategic Command to enhance understanding of nuclear planning and operations. These endeavors hold particular significance for the ROK military, which strongly desires a better understanding of when and how the United States might employ nuclear weapons. Given the small size of the Korean Peninsula, these concerns are entirely justified.

Seventh, the alliance’s joint exercises will enhance the level of realistic training and introduce trilateral exercises that involve Japan. Realistic exercises are essential for building trust in the Yoon administration. With President Yoon aiming to strengthen ties with Japan, their inclusion in trilateral exercises is a logical progression.[11]

Eighth, the United States and ROK will utilize the Regional Cooperation Working Group to enhance maritime domain awareness and foster defense cooperation with other Indo-Pacific partners.[12] Given North Korea’s activities in proximity to South Korean shores and China’s assertive conduct in the region, South Korea has compelling reasons to pursue closer maritime integration.

The Washington Declaration promptly garnered a positive response in both the United States and South Korea, with many regarding the agreement as a tangible effort to enhance American assurance and fortify the alliance. The implementation of the outlined lines of effort commenced almost immediately.

South Korean military delegations promptly traveled to Washington, DC, and Omaha, Nebraska, with the expectation of gaining insight into American plans for the use of nuclear weapons. Understandably, the Yoon administration seeks a deeper understanding of American strategy.

On 18 July, the USS Kentucky (SSBN-737), a ballistic missile submarine, made a port call in Busan. Less than 24 hours later, North Korea conducted two ballistic missile tests in direct response to the Kentucky’s visit.[13] Potentially in reaction to North Korea’s provocation, the USS Annapolis (SSN-760), a Los Angeles-class attack submarine, paid a visit to South Korea’s Jeju Island on 25 July.[14]

The NCG commenced its work in July with the first face-to-face meetings when an American delegation visited South Korea.[15] Defining the precise methods of operation for the group will require time. In essence, the swift transformation of words into actions provides substantial evidence that the Washington Declaration goes beyond mere empty promises.

Nevertheless, analysts on both sides of the Pacific are closely monitoring whether this initial burst of activity will be sustained. Presently, the public commitment from the Biden administration, followed by concrete actions, is achieving the desired effect. The discourse surrounding South Korea’s potential development of its nuclear arsenal has significantly subsided. However, this does not imply that the Yoon administration will abandon the pursuit of a nuclear weapons program if American actions do not align with the threat posed by North Korea.

A renewed commitment from the United States to South Korean security is warmly welcomed by South Koreans, who recall President Richard Nixon’s withdrawal of the Seventh Division from South Korea in 1970, presidential candidate Jimmy Carter’s advocacy for complete withdrawal in 1975, and President Trump’s proposal to withdraw in 2020.[16] Therefore, South Koreans possess a natural inclination to believe that it may only be a matter of time before they find themselves without US forces standing alongside them in a confrontation with North Korea. After all, if the Americans contemplate withdrawal to save resources, there is a concern that they might withdraw to prevent trading Los Angeles for Seoul.

Such sentiments gain further credence from the perceived American restraint in the face of recurrent North Korean provocations.[17] The prevailing thought questions whether the United States would provide a robust response to events such as the North Korean sinking of the ROKS Cheonan in 2010, the shelling of Yeonpyeong Island in 2010, or numerous illicit missile and nuclear tests. This raises doubts about South Korea’s reliance on the United States in defending the ROK during a nuclear conflict.[18] Given North Korea’s rapid advancements in nuclear and ballistic missile technology in recent years, coupled with Kim Jong-un’s directive for “exponential” expansion of his nuclear arsenal, South Koreans have ample reasons for concern.[19]

It should not surprise anyone that the Yoon administration and South Koreans desire consistent and conspicuous demonstrations of American assurance. As part of a broader initiative supported by the Strategic Multilayer Assessment, this article aims to enhance our understanding of how US Strategic Command can more effectively assure the ROK of American commitment to extended deterrence. Consequently, this article initiates with a literature review that explores contemporary perspectives on nuclear assurance, with a particular emphasis on South Korea. It then proceeds to analyze semi-structured interviews conducted with more than a dozen prominent Korean security experts in both the United States and South Korea. Each expert answered a set of questions concerning South Korean support for nuclear weapons and the potential implications for the nation. The article concludes with a series of recommendations designed to assist US Strategic Command in improving assurance efforts.

Literature Review

If Denis Healy, former Defense Minister of the United Kingdom, is correct in asserting that “[i]t only takes five per cent credibility to deter the Russians, but ninety-five per cent to reassure the Europeans,” understanding assurance becomes paramount when examining South Korean perspectives on nuclear weapons.[20] Although there is no single universally accepted definition of assurance, scholars offer valuable explanations and descriptions of this concept.

The earliest definition of assurance is found in Thomas Schelling’s Arms and Influence, where he suggests assurance is a measure of credibility one state has with an adversary in promising not to undertake a negative action.[21] Initially, assurance, according to Schelling and others, primarily related to the perceived capacity to deter. It was only later that deterrence became associated with dealing with adversaries, while assurance became linked with allies.[22] The 2001 Quadrennial Defense Review stands out as one of the earliest defense documents to clearly distinguish between assurance of allies and partners, defining it as one of four key defense policy goals.[23]

In more recent scholarship, David Yost defines assurance as “communicating a credible message of confidence in the dependability of security commitments.”[24] Expanding on this definition in the context of American assurance of South Korea, Go Myung-hyun adds, “Assurance goes beyond effective deterrence as it requires the United States to foster and maintain a firm belief in its allies that it will come to their defense should deterrence fail.”[25] As Go points out, assurance is less about deterring adversaries and more about ensuring that allies feel safeguarded.

Australian scholar Rod Lyon provides further clarification to our understanding of assurance. He proposes that assurance can be categorized into two forms: positive and negative.[26] Positive assurance stems from one country’s commitments to another, outlining specific behaviors in given circumstances, thus reassuring through specific commitments. Negative assurance, on the other hand, arises from one country’s commitment to another regarding actions it will refrain from taking. A similar perspective is shared by Jeffry Knopf, who contends that “Assurances are promises. They involve declarations or signals meant to convey a commitment to take or refrain from taking certain actions in the future.”[27]

Knopf introduces an additional element to consider—reassurance. In this context, one state seeks to convince another state that it holds no hostile intentions and will refrain from taking negative actions. Essentially, reassurance involves persuading a potential adversary that there are no harmful intentions.[28]

David Santoro and John K. Warden explain that assurance can manifest in various forms. Activities such as dialogues, consultations, joint planning, and enhancing relations across diplomatic, informational, military, and economic domains all have the potential to contribute to improved assurance.[29] In both the European and Korean experiences, the presence of US troops serves as a vital tool for assurance.

As the ROK–US alliance celebrated its seventieth year in Washington, DC, in April 2023, it is unsurprising that the alliance has experienced its share of difficulties. North Korea’s initial nuclear weapon test in 2006 fundamentally altered the significance of the alliance with the United States for both South Korea and Japan. According to Keith Payne, the ROK requested the return of nuclear weapons to South Korea for the first time since their withdrawal in 1991.[30] South Korean Defense Minister Yoon Kwang-un urged the United States to declare that any use of nuclear weapons against the ROK would trigger a nuclear response.[31] However, over the years, the United States chose not to reintroduce nuclear weapons to the peninsula. During this period, the DPRK conducted an additional five nuclear tests and developed a range of nuclear-capable short- and long-range ballistic and cruise missiles capable of targeting South Korea and the United States.[32]

The United States’ reluctance to respond robustly to North Korean provocations, such as the sinking of the ROKS Cheonan in 2010 or the shelling of Yeonpyeong Island in the same year, left South Koreans uncertain about US commitment. Additionally, Washington actively worked to dissuade Seoul from mounting forceful responses to these events, a factor that contributed to shaping South Korean perspectives on the credibility of US deterrence.

For South Korea, geography does not offer a favorable position. China, which historically dominated the Korean Peninsula for a millennium, is reasserting itself and presents a long-term challenge for Seoul.[33] The DPRK, governed by a Kim family regime that South Koreans both fear and struggle to comprehend, is rapidly advancing its nuclear and missile capabilities, capable of causing significant harm to South Korea.[34] Russia, too, eyes Korea with aspirations, continually seeking access to warm-water ports and greater strategic flexibility. South Koreans have not forgotten the Japanese occupation of Korea throughout much of the first half of the twentieth century, with its associated horrors.[35] In short, South Korea looks in every direction and perceives threats posed by better-armed powers, leading to concerns about whether the United States would prioritize San Francisco over Seoul.

In 2007, the Department of State’s International Security Advisory Board published the Report on Discouraging a Cascade of Nuclear Weapons States, emphasizing the importance of the nuclear umbrella for American allies. Even then, during a period of relative peace and prior to China and North Korea’s significant nuclear arsenals expansion, the report warned that US assurances were beginning to ring hollow.[36] Despite the United States’ ongoing modernization of the strategic triad, South Koreans harbor a long-standing skepticism about US commitment and view an independent nuclear arsenal, coupled with the presence of US troops, as the preferable option.[37]

Within the English-language scholarly literature, there is limited support for an independent South Korean nuclear arsenal, the return of American nuclear weapons, or any form of nuclear-sharing agreement. Joshua Byun and Do Young Lee specifically argue against a nuclear-sharing arrangement, which is often seen by many South Koreans as a middle-ground solution.[38] According to Byun and Lee, there are four reasons why such an approach is ill-advised. First, there is no common frontline in America’s East Asian alliances. Second, there is a shortage of limited targets to strike. Third, the United States maintains a favorable conventional balance. Fourth, the ROK possesses a superior military compared to the DPRK. Consequently, the return of nuclear weapons to the Korean Peninsula under a nuclear-sharing agreement would be deemed unnecessary.[39]

Furthermore, concerns persist that nuclear sharing could trigger preemptive aggression on the part of North Korea. The rhetoric of former President Trump left many South Koreans apprehensive that the ROK could become entangled in a nuclear conflict between the United States and the DPRK, not of its own making. For some allies, the United States leans excessively on nuclear weapons to ensure security, thereby rendering them a necessity. As pointed out by Alexander Lanoszka, US domestic politics frequently influence Washington’s foreign policy responses to emerging challenges.[40]

The removal of US nuclear weapons from the Korean Peninsula in December 1991 raised concerns among South Koreans. However, with the Cold War drawing to a close, there was substantial optimism that tensions might significantly diminish. The turning point for US–ROK relations occurred in 2000 when South Korea’s president, Kim Dae-jung, shifted to an engagement policy with the DPRK. It was not until North Korea’s first nuclear weapons test in 2006 that South Koreans elected conservative Lee Myung-bak as president. Lee aimed to restore the alliance, and Defense Minister Kim Jae-yong publicly announced that the ROK would request the United States to redeploy nuclear weapons to South Korea by 2010, sending a clear signal of South Korean apprehensions.[41]

Despite ongoing weapons testing and missile development by North Korea, the United States did not return nuclear weapons.[42] Now, more than a decade since South Korea’s request for the return of US nuclear weapons, the country is often described by experts as resembling the United States in its political division.[43] This often results in the presidency alternating between progressives (Democratic Party of Korea, DP) and conservatives (People Power Party, PPP).[44] Progressives favor negotiations with North Korea, while conservatives advocate for stronger ties with the United States and either the return of US nuclear weapons or, preferably, the development of an independent South Korean nuclear arsenal.

Prior to the narrow election of conservative Yoon Suk-yeol in March 2022, progressive Moon Jae-in (2017–2022) led a largely unsuccessful effort to improve inter-Korean relations.[45] Moon’s endeavors concluded much like previous South Korean de-escalation efforts, with continued North Korean nuclear and missile development. Donald Trump’s presidency coincided with the Moon administration, catching South Koreans largely unprepared. The deployment of Terminal High Altitude Area Defense (THAAD) ballistic missiles deeply offended Beijing, which imposed economic sanctions on South Korea.[46] President Trump’s public questioning of the US–ROK alliance and willingness to bypass President Moon to engage directly with Kim Jong-un often left the Moon administration on the defensive, questioning whether the United States would provide support if North Korea took aggressive action against the South.

For North Korea and the Kim regime, periodic strains in the US–ROK relationship are perceived as a positive sign that the DPRK’s strategy is effective. As noted by Go Myung-hyun, the DPRK considers regular US–ROK military exercises akin to North Korean nuclear tests. Thus, North Korea aims to ultimately create a disconnect in threat perception between Washington and Seoul by heightening its nuclear threats. As Go asserts, “Ultimately, North Korea aims to decouple threat perception between Washington and Seoul by heightening its nuclear threats. Pyongyang is inciting decoupling between Washington and Seoul by sowing doubts about US extended deterrence. This shows that undermining assurance is also an important North Korean strategic objective.”[47]

Cho Young-won presents three reasons why North Korea pursued and continues to engage in provocative actions related to its nuclear program. First, the DPRK’s conventional capabilities weakened, while the ROK achieved conventional superiority, making nuclear weapons the most cost-effective choice (costing USD 3 billion in the first decade). Second, the DPRK’s apprehensions of a potential US nuclear strike heightened following the collapse of the Soviet Union and a decrease in Chinese commitment. Third, nuclear weapons serve as the most effective means to ensure the survival of the regime. In essence, North Korea’s strategy represents a form of “poor man’s deterrence.”[48] It is crucial to keep in mind that the Kim regime still aspires to reunify the peninsula under the North Korean flag, and undermining the US–ROK alliance remains a top priority for Kim Jong-un.

South Korean public opinion consistently supports the return of American nuclear weapons or, as indicated by survey respondents, the development of an independent South Korean nuclear arsenal as a deterrent against this threat.[49] The following section outlines the methodology employed in interviews with experts who possess insights into South Korean perspectives on nuclear weapons. These experts were drawn from inside and outside government and from the United States and South Korea.


To gain profound insights into South Korean perspectives regarding the utility of nuclear weapons, we employed the structured interview technique. We conducted interviews with over a dozen American and South Korean experts, specifically chosen for their expertise in Korean security and familiarity with South Korean public opinion polls concerning nuclear weapons. As these interview participants had close affiliations with either the United States or South Korean governments, serving as military officers, civil servants, or experts linked to government-related think tanks, I ensured their anonymity.

I selected interviews as the methodological approach because this article focuses on gaining a deeper understanding of how the United States and US Strategic Command can enhance the assurance of American extended deterrence to South Korea. As part of this endeavor, gaining a more detailed understanding of South Korean perspectives on security threats, the return of American nuclear weapons, and the desire for an indigenous nuclear weapons program was crucial. If an interview is defined as “a conversation with a purpose,” then the qualitative interview, which captures an individual’s perspectives, experiences, emotions, and narratives with guidance from the interviewer, is an appropriate method to achieve my desired outcomes.[50]

Admittedly, interviews come with various strengths and weaknesses and are not universally suitable for all research.[51] As a research method, interviewing represents an intensive approach to data collection, aimed at gathering information about participants’ experiences, viewpoints, and beliefs.[52] The use of structured interviews, and allowing participants to provide information beyond the predefined set of questions, offers flexibility in the interview process.[53]

For this specific research project, the primary risk associated with the interview process was the potential oversight of South Korean cultural norms and expectations.[54] To mitigate this risk, both the set of questions and the interview approach underwent scrutiny by American personnel with experience in Korea and familiarity with South Korean cultural norms. This refinement enhanced the design of culturally sensitive questions, ensuring they were posed within an appropriate cultural context.

The structured interview approach chosen was not intended to yield quantitative data. Given the limited number of Korean security subject matter experts who also possess knowledge of South Korean public opinion, this method was deemed appropriate. It is worth noting that Margaret Harrell and Melissa Bradley’s Data Collection Methods: Semi-Structured Interviews and Focus Groups provides a comprehensive guide for designing questionnaires, like the one used in this study.[55] In summary, the approach adopted— structured interviews—proved to be the optimal methodology.

More than a dozen subject matter experts from both the United States and South Korea participated in these interviews, conducted via Microsoft Teams and averaging 60–90 minutes each. The results of these interviews offer significant clarity in understanding South Korean public opinion and the perspectives of experts who specialize in the issues under discussion. As expected, there were nuances, which we discuss in the following section.


Participants in these interviews were drawn from both the American and South Korean military, civil service, and think tanks, many of which had close government affiliations. Individual anonymity has been preserved in the subsequent analysis, aiming to provide interviewees with the freedom to candidly respond to questions. The analysis that follows reveals intriguing patterns in their responses. Despite participants holding political views spanning the left, right, and center, it was often their nationality—rather than their political perspective—that emerged as the most significant factor influencing their outlook. In essence, American and South Korean subject matter experts exhibit distinct perspectives on the nuclear issue, suggesting that Miles’ Law may apply to nationality as effectively as it does to bureaucratic position.[56]

Below is an analysis of participant responses, structured according to the sequence in which the nine questions were presented during the interviews. Each question is accompanied by a description and an analysis of the responses. Notably, when participants diverged from the specific questions and delved into broader topics, they provided some of the most insightful information, and these insights are also included.

Over the past decade, a number of public opinion polls show that an increasing percentage of South Koreans support nuclear weapons in South Korea—either a return of American nuclear weapons or an independent South Korean nuclear arsenal. What are the reasons motivating this increase in support for nuclear weapons in South Korea?

For more than a decade, public opinion polling in South Korea consistently indicates that citizen support for the return of American nuclear weapons or the development of an indigenous nuclear arsenal remains at around 70 percent. This figure declines significantly when respondents are informed about potential sanctions that might accompany South Korea’s pursuit of nuclear weapons.[57] Interview participants unanimously concurred that the primary driving force behind South Korean support for nuclear weapons is the DPRK’s expanding nuclear arsenal. As one Korean participant emphasized, “Koreans want to be liberated from fear.” Additionally, South Koreans favor an indigenous nuclear arsenal to a lesser extent for reasons of prestige. To echo the sentiments of most American and South Korean participants, if a relatively impoverished and underdeveloped country like North Korea can assemble a nuclear arsenal, why can’t South Korea?

There was widespread consensus that the public leans toward the development of an indigenous nuclear arsenal rather than a return of American nuclear weapons. South Korean interviewees pointed out that the most significant factor influencing support for nuclear weapons is political affiliation, with conservatives displaying a much higher likelihood of endorsing nuclear weapons compared to progressives. Politics in South Korea closely mirror those in the United States.[58]

Finally, interview participants suggested that many South Koreans harbor concerns about the credibility of American extended deterrence. As mentioned earlier, three past presidents flirted with the idea of withdrawing American troops from South Korea, leading many South Koreans to apprehend that the United States might not prioritize its commitments to Seoul over its own national security. There are also fears that in the event of a conflict between China and the United States, South Korea could be left vulnerable.[59] Consequently, an indigenous nuclear arsenal is viewed as the optimal choice, or at the very least, a return of US nuclear weapons could serve as evidence of US commitment to ROK security.

What do South Koreans think about the ramifications of both a return of American nuclear weapons and an independent South Korean nuclear arsenal?

Opinion polls over the past decade have rarely included specific questions regarding the public’s awareness of the potential costs associated with either an indigenous nuclear weapons program or the return of American nuclear weapons. However, the KINU Unification Survey 2023, published in June, delved into previous survey responses and posed more detailed questions to current respondents regarding nuclear weapons and their consequences.[60] For instance, when survey participants were presented with a general inquiry about their support for nuclear weapons in South Korea, 60 percent expressed support. However, when given the choice between maintaining American troops in South Korea or pursuing an indigenous nuclear weapons program, backing for nuclear weapons dropped dramatically.[61] As one South Korean interviewee emphasized, “We should not exchange the alliance for nuclear weapons.”

The South Korean public’s limited understanding of the potential costs associated with nuclear weapons, whether US or indigenous, was a point of unanimous agreement among both American and South Korean interview participants. South Koreans, for instance, rarely contemplate the likely ramifications of withdrawing from the Treaty on the Nonproliferation of Nuclear Weapons (NPT). They possess only a vague notion of the costs associated with a nuclear weapons program. While South Korean experts within government and major think tanks have a better grasp of these costs, they, too, are largely unfamiliar with the specific sanctions stipulated in US law.[62]

Interview participants anticipate that the United States would impose sanctions on South Korea if it were to pursue an indigenous weapons program. However, South Korean participants expressed optimism that the United States would treat South Korea similarly to Pakistan after discovering its nuclear weapons program and, subsequently, after conducting a nuclear test in 1998—imposing limited sanctions for a brief period. For South Korean proponents of nuclear weapons, the preferred option is the development of an indigenous arsenal that would position South Korea akin to the United Kingdom, as a nuclear-armed ally of the United States.

How do you see South Koreans weighing the return of American nuclear weapons versus an independent South Korean nuclear arsenal? Do they prefer one over the other?

Both American and South Korean interview respondents agreed that the majority of South Koreans favor the development of an indigenous nuclear arsenal. As previously discussed, the concern that the United States might prioritize the defense of San Francisco over Seoul, coupled with South Koreans’ perception of their global standing, drives their preference for an independent arsenal. Nevertheless, some older South Koreans and defense experts view the return of US nuclear weapons as a compromise solution that enhances ROK security while averting sanctions from the United States, the Nuclear Suppliers Group, the United Nations, and other international organizations. As one South Korean participant articulated, “A US return allows Koreans to have their cake and it eat too.”

Are other measures of American assurance, such as increased military integration, public statements of commitment, and expanded information sharing, adequate demonstrations of American commitment to ROK security?

One South Korean participant succinctly summarized the perspective of many South Koreans with the phrase, “You can never say I love you too much.” Consistent with this sentiment, both American and South Korean participants indicated that the Washington Declaration and its initial efforts are already enhancing assurance. South Korean participants emphasized the importance of ongoing information sharing, the integration of nuclear planning and operations, and the deployment or stationing of strategic assets in South Korea. Additionally, it was suggested that in the absence of a return of nuclear weapons to South Korea, the nuclear submarine-launched cruise missile was the preferred option because it offers greater tactical utility compared to a submarine-launched ballistic missile.

One South Korean expert noted that the assurance challenge primarily involves the United States and the ROK defense community, as they are concerned that Americans might be diverted from Korean security in the event of a Taiwan conflict. There is apprehension that North Korea could take advantage of such a situation to alter the status quo. Therefore, the desire for closer integration between US Strategic Command and South Korea’s new Strategic Command is of utmost importance.[63] South Korean defense experts, like many of their American counterparts, view the possibility of conflict between China and the United States as a significant and definite challenge for the ROK.

How do South Koreans think the United States would respond to ROK efforts to build an independent nuclear arsenal?

Without reiterating the previously mentioned points, it’s essential to acknowledge that there is no unanimous consensus among experts, whether American or South Korean, regarding the actions that the United States or the international community might take if South Korea were to develop nuclear weapons. South Korean public opinion on this matter is also divided. According to South Korean interview participants, the occupant of the White House is arguably the most significant factor in determining any US response.

Does South Korean elite opinion differ markedly from the broader public’s view on nuclear weapons and the impact of developing a nuclear program?

For more than a decade, the South Korean public consistently showed higher support for nuclear weapons compared to South Korean elites. However, this trend is undergoing a shift as a larger proportion of elites are now expressing support for the return of nuclear weapons, whether American or indigenous. The elite class’s understanding of the economic and security implications of an indigenous nuclear weapons program consistently drove down support, even though elites, both in and out of government, were generally more skeptical of US extended deterrence. The growing nuclear arsenal of the DPRK and the United States’ perceived failure to deter Kim Jong-un’s ambitions are causing both the public and elite opinion to align more closely on this issue.

During an interview with a South Korean expert, it was emphasized that fewer than a dozen specialists are actively driving the debate in South Korea. There is a notable scarcity of individuals with even a basic understanding of nuclear deterrence and proliferation. Interestingly, the Korean security experts interviewed for this study were all well-versed in South Korean public opinion polls and their results, which greatly contributed to understanding Korean perspectives.

How do South Koreans and their political leaders think China will respond to either the return of American nuclear weapons to the Peninsula or an independent Republic of Korea nuclear program?

For readers unfamiliar with South Korea’s perspective, it is crucial to recognize that any discussion about China posing a threat to the ROK is an extremely sensitive topic. The People’s Republic of China is South Korea’s largest trading partner and has shown a willingness to leverage its economic power to retaliate against any criticism it disagrees with. This creates a situation of “China restraint,” where South Korean defense experts are hesitant to openly criticize China due to the economic repercussions it could entail. South Korean concerns in this regard are entirely reasonable. For instance, when the United States deployed THAAD ballistic missile defenses to South Korea in 2017, China used its economic leverage to pressure and punish South Korea.[64] This sensitivity is challenging for Americans to fully grasp given their global position.

Nevertheless, among South Korean participants, there was an acknowledgment that China is becoming an increasingly significant concern. The ongoing actions of Xi Jinping, in particular, raise worries. These experts held varying views on how China might react to an indigenous South Korean nuclear program. While there was an expectation of Chinese sanctions, some believed that China might not view a South Korean arsenal as a direct threat, understanding the intention to deter North Korean ambitions. From the South Korean perspective, the worst-case scenario would involve China increasing its support for the DPRK.

If the Republic of Korea were to develop an independent nuclear arsenal, what would be the main objectives of the effort—diplomatic, military, economic?

As expressed by one South Korean participant, the prevailing sentiment can be summed up as “DPRK, DPRK, DPRK!” It comes as no surprise that the looming threat posed by North Korea’s nuclear arsenal was the predominant reason cited by experts for considering the pursuit of an indigenous nuclear arsenal. Additionally, some mentioned that South Korea’s interest in nuclear weapons also carries an element of prestige. As one South Korean interviewee remarked, “Security is the only reason, but some talk about prestige.” It is important to note that the significance of prestige only arises because of the DPRK’s expanding arsenal. In the absence of North Korea’s nuclear threat, there would be minimal support for nuclear weapons in South Korea.

What do South Koreans and their political leaders think about the American role in the North Atlantic Treaty Organization (NATO) versus Korea—as it relates to nuclear weapons?

Both American and South Korean participants reached a consensus that the South Korean public desires an alliance akin to NATO, driven by the perception that the European alliance is stronger than American commitment to the ROK. The NATO dual-capable aircraft mission holds appeal for the ROK military, as it is viewed as the most practical means to exhibit nuclear deterrence, involving F-35s equipped with B61 nuclear gravity bombs. However, there exists a widespread misunderstanding among most South Koreans regarding NATO’s nuclear mission, with a mistaken belief that NATO member-states have considerably more access and authority over American nuclear weapons than is the reality. The collective defense obligations outlined in the Atlantic Charter’s Article 5 are perceived as placing a much more robust requirement on the United States to defend NATO compared to the obligations in the US–South Korea Mutual Defense Treaty.[65]

In 2022, South Korea initiated a mission to NATO, partly with the aim of gaining deeper insights into the inner workings of the alliance.[66] As the sole alternative to the US–South Korea alliance, South Koreans seek a better understanding of NATO, contemplating whether modifications should be pursued in their own alliance with the United States. Additionally, there exists an unspoken concern among many South Koreans that the United States might be more committed to defending NATO, driven by the fact that most Americans can trace their ancestry to Europe. This suspicion has been exacerbated by periodic suggestions from US presidents about the potential withdrawal of US troops from South Korea.

The analysis of interview responses provides valuable insights into the perspectives of the South Korean public and Korean security experts. The following recommendations are aimed at outlining ways in which US Strategic Command can bolster South Korean assurance, particularly in the face of growing belligerence from both North Korea and China.


The work of scholars examining assurance and the insights gathered from interview participants contribute to the formulation of recommendations that could aid US Strategic Command in reinforcing American assurance of South Korea. While it is acknowledged that not all these recommendations may be feasible for various reasons, they warrant consideration as the command assumes a more significant role in assuring South Korea and the broader Asian region. The introductory sections of this study outlined the eight main lines of effort within the Washington Declaration, and several of these efforts are detailed below.

First, reassess the classification requirements for information that can be shared with the ROK. South Korea’s primary aspiration is to gain deeper insights into how the United States approaches the use of nuclear weapons. Reviewing classification guidelines, including involving the South Korean liaison officer at STRATCOM in more discussions, could substantially enhance assurance.

Second, conduct classified wargames in collaboration with the ROK that incorporate scenarios involving North Korean nuclear weapon use and potential US nuclear responses. Even if these wargames take the form of tabletop exercises, they can offer South Korea valuable insights into American strategic thinking. Developing a shared operational understanding of when and how the United States would react to a North Korean nuclear event is a key objective of such exercises.

Third, provide support to the ROK in establishing its new Strategic Command. While United States Forces Korea and Combined Forces Command have a well-established history of collaboration with the South Korean military, assisting in the development of a strategic culture within the ROK will further strengthen mutual trust. Embedding STRATCOM personnel within the new command structure would be mutually beneficial for both nations.

Fourth, establish a mechanism for South Korean intelligence, military, and foreign affairs professionals to contribute to American understanding of the DPRK. South Koreans possess invaluable insights into the workings of the Kim regime that surpass American understanding. Creating a platform for them to enhance their input will grant the ROK a voice they currently feel is lacking.

Fifth, maintain the initiatives that have emerged from the Washington Declaration. These efforts have proven effective by all accounts. A recent visit to Seoul by General Anthony Cotton, the Commander of US Strategic Command, exemplifies actions demonstrating the United States’ commitment to Korean security.[67]

Sixth, integrate nuclear weapons into existing ROK–US joint exercises. This will afford South Koreans the opportunity to operate in scenarios where nuclear weapons are a factor. Such a visible display of US commitment holds significant importance for South Korea.

Seventh, deploy strategic assets to South Korea. While the port call of the USS Kentucky in Busan clearly signaled US commitment, periodic deployments of B-52s, for instance, would serve as a robust demonstration of US assurance.[68]

Eighth, assist the South Korean military in developing a comprehensive training program encompassing nuclear deterrence theory, strategy, policy, nuclear weapon physics, effects, and radiological response. Establishing a dedicated career field within the ROK army akin to the US Army’s Nuclear and Countering Weapons of Mass Destruction (CWMD) Functional Area 52 can enhance South Korea’s understanding of the multifaceted aspects of nuclear conflict and deterrence.

Ninth, institute a professional continuing education program (unclassified and one-week-long) targeting government officials, military officers, and defense academics. This program would provide participants with a foundational understanding of nuclear strategy, operations, and policy. Given the limited knowledge of these subjects among South Koreans who influence policy and public opinion, improving their comprehension can help demystify these crucial matters.

Tenth, reconsider sending South Korean government officials, military delegations, and defense experts to Washington, DC, during their visits to the United States. The nation’s capital often lacks the necessary nuclear expertise. South Koreans are more interested in gaining insights into nuclear operations than the broader policy toward the ROK. Visits to operational bases, weapons labs, and other tangible manifestations of US extended deterrence serve as more effective assurance mechanisms. Additionally, it is essential to diversify the voices South Koreans hear during these visits, rather than repeatedly presenting the same perspectives.


In conclusion, the insights gleaned from the preceding pages underscore the complex nature of the assurance challenge with South Korea. It becomes evident that there is no single, straightforward solution to address the concerns of South Koreans, who rightfully harbor apprehensions about both North Korean aggression and the prospect of US disengagement. The historical backdrop reminds us that since the armistice in 1953, North Korea has initiated over 220 provocations, some of which could be deemed acts of war.[69] Furthermore, as highlighted earlier, three past US presidents have entertained the idea of withdrawing US troops from the ROK, adding to South Korea’s unease.

Moreover, it is crucial to recognize the larger geopolitical context in which these dynamics are unfolding. China, in its quest to regain dominance in Asia, poses an additional challenge that South Korea must contend with. Given these multifaceted threats, it becomes clear that assuring South Korea effectively to dissuade the pursuit of an indigenous nuclear arsenal requires a comprehensive approach that goes beyond merely maintaining an American tripwire force on the Korean Peninsula.

To bolster South Korean confidence and commitment to the alliance, a multifaceted strategy must encompass information sharing, joint wargaming, integration of nuclear capabilities, collaboration in the establishment of South Korea’s Strategic Command, and enhancing mutual understanding of each nation’s perspectives and concerns. It is incumbent upon US Strategic Command to actively engage in these efforts to strengthen US assurance of South Korea in an era where North Korea and China pose increasingly complex challenges to regional stability.

In the face of these intricate dynamics, the path forward demands continued collaboration and adaptability on the part of both nations. By addressing the multifaceted dimensions of the assurance challenge and fostering a deeper, mutual understanding, the United States can work alongside South Korea to build a more secure and stable future for the region. ♦

Adam B. Lowther, PhD

Dr. Lowther, a nuclear deterrence expert, currently serves as the Vice President of Research at the National Institute for Deterrence Studies and host of Nuclecast. This article was written for the National Strategic Research Institute (NSRI) and sponsored by the Strategic Multilayer Assessment. Dr. Lowther’s extensive background includes directing multi-domain operations programs at the Army Management Staff College (AMSC) and teaching at the Army’s School of Advanced Military Studies (SAMS).

He also served as the founding director of the School of Advanced Nuclear Deterrence Studies (SANDS) at Kirtland AFB and directed the Center for Academic and Professional Journals at the Air Force Research Institute (AFRI), overseeing publications like Strategic Studies Quarterly and the Air & Space Power Journal. Dr. Lowther is a prolific author and contributor to various publications, including the New York Times, Boston Globe, Joint Force Quarterly, and Strategic Studies Quarterly.1



[1] Sang-Hun Cheo, “In a First, South Korea Declares Nuclear Weapons a Policy Option,” New York Times, 12 January 2023,

[2] See: Scott Berrier, North Korea Military Power (Washington, DC: Defense Intelligence Agency, 2021).

[3] Sangyong Son and Man-Sung Yim, “Correlates of South Korean Public Opinion on Nuclear Proliferation,” Asia Survey 61, no. 6 (2021): 1028–57,; and Toby Dalton, Karl Friedhoff, and Lami Kim, Thinking Nuclear: South Korean Attitudes on Nuclear Weapons (Chicago: The Chicago Council on Global Affairs, 2022), 3–4.

[4] Jennifer Ahn, “Beyond US Credibility Concerns: Factors Driving the Nuclear Weapons Debate in South Korea,” Korea Economic Institute, 17 February 2023,

[5] Jessica Corbett, “​‘Outrageous’: South Korean President Under Fire for Considering Nuclear Weapons,” Common Dreams, 12 January 2023,

[6] Justin Sink and Jenny Leonard, “Biden Plans to Host Spring State Dinner for South Korea’s Yoon,” Bloomberg, 15 February 2023,

[7] “Republic of Korea State Visit to the United States” (fact sheet, The White House, 26 April 2023),

[8] Mitch Shin, “Yoon and Biden Announce, ‘Washington Declaration’ to Lock in Nuclear Deterrent,” The Diplomat, 27 April 2023,

[9] Victor Cha, “The U.S.-ROK Nuclear Consultative Group’s Successful Launching,” Center for Strategic and International Studies, 20 July 2023,

[10] Daehan Lee, “South Korea to Create New Command that Would Control Strategic Weapons,” Defense News, 11 July 2022,

[11] Tim Kelley, “Japan Welcomes Thaw with South Korea in Gloomy Annual Security Assessment,” Reuters, 27 July 2023,

[12] “Washington Declaration” (press release, The White House, 26 April 2023), .

[13] Luis Martinez, “North Korea Launches Ballistic Missiles after US Nuclear-capable Sub Arrives in South Korea,” ABC News, 18 July 2023,

[14] Mike Glenn, “Second US Submarine Docks in South Korea Amid North Korean Threats,” Washington Times, 25 July 2023,

[15] Eunice Kim, “US, South Korea Kick Off Nuclear Consultative Group in Seoul,” Voice of America News, 18 July 2023,

[16] Don Oberdorfer and Robert Carlin, The Two Koreas (New York: Basic Books, 2014), 52–71; David Choi, “Trump Considered ‘Complete Withdrawal’ of US Troops from South Korea, Former Defense Chief Says,” Stars and Stripes, 10 May 2022,; and Veronica Stracqualursi, “Trump Apparently Threatens to Withdraw US Troops from South Korea Over Trade,” CNN, 16 March 2018,

[17] Scott Snyder and See-Won Byun, “Cheonan and Yeonpyeong,” RUSI Journal 156, no. 2 (2010): 74–81.

[18] So Gu Kim, “Forensic Seismology Vis-à-Vis an Underwater Explosion for the ROKS Cheonan Sinking in the Yellow Sea of the Korean Peninsula,” International Journal of Physics Research and Applications 6 (2023): 73–89,; “North Korean Artillery Hits South Korean Island,” BBC, 23 November 2010, ‎; and Missile Defense Project, “North Korean Missile Launches & Nuclear Tests: 1984-Present,” Center for Strategic and International Studies, 23 April 2023,

[19] Associated Press, “North Korea’s Kim Orders ‘Exponential’ Expansion of Nuclear Arsenal,” National Public Radio, 1 January 2023,

[20] Michael Ruhle, “Deterrence: What It Can (and Cannot) Do,” NATO Review, 20 April, 2015,

[21] Thomas Schelling, Arms and Influence (New Haven, CT: Yale University Press, 1966), 74.

[22] Jeffrey Knopf, “Varieties of Assurance,” Journal of Strategic Studies 35, no. 3 (2012): 375–99.

[23] Donald Rumsfeld, Quadrennial Defense Review (Arlington, VA: Department of Defense, 2001), 14.

[24] David Yost, “Assurance and US Extended Deterrence in NATO,” International Affairs 85, no. 4 (2009), 775.

[25] Myong-Hyun Go, North Korean Provocations and the Challenges for the ROK-US Alliance (Seoul: Asan Institute for Policy Studies, 2022), 7–9.

[26] Rod Lyon, “The Challenges Confronting US Extended Nuclear Assurance in Asia,” International Affairs 89, no. 4 (July 2013); 929–41,

[27] Jeffrey Knopf, Security Assurances and Nuclear Nonproliferation (Stanford: Stanford University Press, 2012), 3.

[28] Knopf, Security Assurances, 14.

[29] David Santoro and John K. Warden, “Assuring Japan and South Korea in the Second Nuclear Age,” Washington Quarterly 38, no. 1 (Spring 2015): 147–65.

[30] Hans Kristensen and Robert Norris, “A History of US Nuclear Weapons in South Korea,” Bulletin of the Atomic Scientist 73, no. 6 (2017), 349–57.

[31] Keith B. Payne, “On Nuclear Deterrence and Assurance,” Strategic Studies Quarterly 3, no. 1 (Spring 2009): 43–80,

[32] Terrence Roehrig, “The US Nuclear Umbrella over South Korea: Nuclear Weapons and Extended Deterrence,” Political Science Quarterly 132, no. 4 (Winter 2017–2018): 651–84,

[33] Taylor Washburn, “How an Ancient Kingdom Explains Today’s China-Korea Relations,” The Atlantic, 15 April 2013,

[34] See: Jung H. Pak, Becoming Kim Jung Un (New York: Ballantine Books, 2020).

[35] “South Korea and Japan’s Feud Explained,” BBC, 2 December 2019,

[36] Charles R. Robb, Report on Discouraging a Cascade of Nuclear Weapons States (Washington, DC: Department of State, 2007).

[37] Alexander Lanoszka, Atomic Assurance: The Alliance Politics of Nuclear Proliferation (Ithaca, NY: Cornell University Press, 2018), 57, 110–30; “Nuclear Weapons: Why South Koreans Want Them,” BBC, 22 April 2023,; and Son and Yim, “Correlates of South Korean Public Opinion.”

[38] Joshua Byun and Do Young Lee, “The Case Against Nuclear Sharing in East Asia,” Washington Quarterly 44, no. 4 (Winter 2021): 67–87.

[39] Byun and Lee, “The Case Against Nuclear Sharing,” 75.

[40] Lanoszka, Atomic Assurance, 44.

[41] Scott Snyder and Joyce Lee, “Infusing Commitment with Credibility: The Role of Security Assurances in Cementing the US-ROK Alliance,” in Security Assurances and Nuclear Nonproliferation, ed. Jeffrey Knopf (Stanford: Stanford University Press, 2012), 175.

[42] See: Missile Defense Project, “Missiles of North Korea,” Center for Strategic and International Studies, 22 November 2022,; and Mary Beth Nikitin, North Korea’s Nuclear Weapons and Missile Programs (Washington, DC: Congressional Research Service, 2023).

[43] Duyeon Kim, “How to Keep South Korea from Going Nuclear,” Bulletin of the Atomic Scientist 76, no. 2 (2020): 69–74. See also: Lami Kim, “South Korea’s Nuclear Hedging?,” Washington Quarterly 41, no. 1 (2018): 115–33.

[44] TK, “South Korea’s Political Parties: The Basics,” The Blue Roof, 6 September 2020,

[45] Choe Sang-Hun, “Yoon Suk-yeol, South Korean Conservative Leader, Wins Presidency,” New York Times, 9 March 2022,; and Charlie Campbell, “The Negotiator,” Time, 4 May 2017,

[46] Kim, “South Korea’s Nuclear Hedging?”116–17.

[47] Go Myong-Hyun, North Korean Provocations and the Assurance Challenge for the ROK-US Alliance (Seoul, Asan Institute for Policy Studies, 2022), 8.

[48] Young-won Cho, “Method to the Madness of Chairman Kim: The Instrumental Rationality of North Korea’s Pursuit of Nuclear Weapons,” International Journal 69, no. 1 (2014): 5–25; and Christy Lee, “North Korea Likely to Continue Escalating Threats Next Year, Experts Say,” Voice of America, 7 December 2022,

[49] Son and Yim, “Correlates of South Korean Public Opinion,” 1–30; Dalton, Friedhoff, and Kim, Thinking Nuclear, 3–4; and Kim, “How to Keep South Korea from Going Nuclear,” 68–75.

[50] R. Kahn and C. Cannell, The Dynamics of Interviewing: Theory, Technique and Cases (Oxford: Wiley and Sons, 1957), 149; and Felice Billups, Qualitative Data Collection Tools (Thousand Oaks, CA: Sage Publications, 2021), 36.

[51] Billups, Qualitative Data Collection Tools, 37–40.

[52] Carl Patton and David Sawicki, Basic Methods of Policy Analysis and Planning (Englewood Cliffs, NJ: Prentice Hall, 1993), 97; and Sylvie D. Lambert and Carmen G. Loiselle, “Combining Individual Interviews and Focus Groups to Enhance Data Richness,” Journal of Advanced Nursing 62, no. 2 (2008): 228–37,

[53] Frances Ryan, Michael Coughlan, and Patricia Cronin, “Interviewing in Qualitative Research: The One-to-One Interview,” International Journal of Therapy and Rehabilitation 16, no. 6 (2009), 310.

[54] Eva Codo, “Interviews and Questionnaires,” in The Blackwell Guide to Research Methods in Bilingualism and Multilingualism, ed. Li Wei and Melissa J. Moyer, (New York: Blackwell, 2008), 162.

[55] Margaret Harrell and Melissa Bradley, Data Collection Methods: Semi-Structured Interviews and Focus Groups (Arlington, VA: RAND Corporation, 2009).

[56] Rufus Miles, “The Origin and Meaning of Miles Law,” Public Administration Review 38, no. 5 (1978): 399–403. Miles’ Law suggests where you sit (position), determines where you stand (on an issues).

[57] See: Sang Sin Lee et al., KINU Unification Survey 2023: Public Opinion on South Korea’s Nuclear Armament (Seoul: Korean Institute for National Unification, 2023),

[58] Yoon Chae-yung, “Public Opinion Poll: 35.2% of Its Own Nuclear Armament, 16% of the United States' Tactical Nuclear Redeployment, 40% of Maintaining Denuclearization,” Newspim, 10 October 2022,

[59] Leon Whyte, “Evolution of the U.S.-ROK Alliance: Abandonment Fears,” The Diplomat, 22 June 2015,

[60] Sang et al., KINU Unification Survey 2023.

[61] Sang et al., KINU Unification Survey 2023, 21.

[62] Newell Highsmith, “Would the US Sanction Allies Seeking the Bomb?,” Carnegie Endowment for International Peace, 20 April 2023,

[63] Shin Ji-hye, “Military to Establish ‘Strategic Command’ by 2024 to Control Three-axis System,” Korea Herald, 6 July 2022,

[64] Ethan Meick and Nargiza Salidjanova, China’s Response to U.S.-South Korean Missile Defense System Deployment and its Implications (Washington, DC: US-China Economic and Security Review Commission, 2017),

[65] Katherine Ebright, “NATO’s Article 5 Collective Defense Obligations, Explained,” Brennan Center, 15 November 2022,; and Emma Chanlett-Avery and Caitlin Campbell, US-South Korea Alliance: Issues for Congress (Washington, DC: Congressional Research Service, 2022).

[66] Nam Hyun-woo, “South Korea’s Mission to NATO Approved,” Korea Times, 28 September 2022,

[67] Unshin Lee Harpley, “Cotton Talks Extended Deterrence in First Visits to Japan, S. Korea as STRATCOM Boss,” Air & Space Forces Magazine, 5 September 2023,

[68] Richard Pollina, “Nuclear Sub USS Kentucky Makes First Port Call in South Korea in Four Decades,” New York Post, 18 July 2023,

[69] Shin Hea-in, “N.K. Commits 221 Provocations Since 1953,” Korea Herald, 5 June 2011,


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