Cost and Benefit Analysis on US’s ‘Flexible Nuclear Redeployment’ on Korean Peninsula 

Bee Yun Jo

Research Fellow, Sejong Institute

Summary

 1. Introduction

This paper focuses on the concept of ‘flexible redeployment’—namely, base modernization to enable potential, temporary, and/or emergency deployment of U.S.‘s tactical nuclear weapons on the Korean Peninsula. Elaborating flexible redeployment as the most plausible means to entice U.S.’s increased nuclear presence in the region, this paper aims to provide a rough guesstimate for initial upfront costs as well as pros and cons of such arrangement in Seoul’s perspective. For cost estimation, this study brought together David Philips’ cost estimation for deploying 100 B61-12s at Kunsan Air Base(KRW 3.6 to 5.2 trillion) as well as the FY2024 U.S. defense budget related to restoring the ‘surety mission’ at the Lakenheath Air Base in UK.

As brief overview, this study estimates that the initial upfront cost of flexibly deploying between 1 and 20 B61-12 gravity bombs on Kunsan AB would amount to approximately KRW 773.3 billion to 924.3 billion (USD 567 million to 677.6 million). The identified benefits of flexible redeployment include: (1) relative feasibility (as to permanent redeployment), (2) provision of new emergency deterrence option against North Korean threats; and (3) function as stimulus to sustained U.S.–ROK consultation, training, operationalization of conventional-nuclear integration(CNI). However, this model also presents limitations: (1) the implicit signal it may send as part of broader efforts to counter China, which could risk Chinese retaliation; (2) constraints inherent in the concept of “flexibility” itself; and (3) the likelihood of requiring upto 50% increase in South Korea’s defense cost-sharing burden, as the initial cost estimated to be about 51–61% of current defense cost sharing budget. Based on this cost-benefit assessment, the paper concludes with some policy recommendations.

2. Trump 2.0 and Nuclear Redeployment

a. U.S. Strategic Priorities: Making Force Posture More China-focused

The U.S is increasingly likely to restructure its defense strategy around two central priorities: homeland defense and China threat. This shift is reflected in the Interim National Defense Strategic Guidance, which was internally circulated by the U.S. Department of Defense in March 2025. The guidance outlines an ongoing comprehensive review of the size, capabilities, and posture of U.S. forward-deployed forces worldwide including USFK and USFJ. Notably, Elbridge Colby, the Under Secretary of Defense for Policy and the leading architect of the forthcoming National Defense Strategy (NDS), has emphasized that North Korea is not America’s primary threat. He also argues that U.S. Forces Korea (USFK) should be more closely integrated into the framework of deterring China, and that South Korea must assume “overwhelming responsibility” for its own defense. Dan Cain, the nominee for Chairman of the Joint Chiefs of Staff, has also stated that he will review the scale of U.S. troop deployments in South Korea and Japan and provide recommendations to the Secretary of Defense and the President—signaling the possibility of a realignment of U.S. forces in both countries.

This strategic reorientation is closely tied to evolving security dynamics in the Indo-Pacific region. China’s conventional force buildup, the simultaneous enhancement of nuclear capabilities by North Korea, China, and Russia, and the rising threat landscape in new domains such as cyberspace, drones, and outer space are placing growing pressure on U.S.‘s overseas military presence. In this context, discussions on tactical nuclear redeployment within the United States are increasingly being considered as part of a broader effort to recalibrate American posture in the Indo-Pacific. In particular, there is a growing bipartisan consensus around the need for limited nuclear options in the region.

b. Constraints: U.S. Tactical Nuclear Arsenal and Quantitative Limitations

Despite growing momentum in discussions on tactical nuclear redeployment, a critical constraint remains: the limited number of tactical nuclear weapons currently available to the United States. In particular, the U.S. lacks sufficient inventory to permanently deploy e.g. 100 B61-12 tactical nuclear bombs to the Korean Peninsula. As of 2025, the United States possesses an estimated 200 B61-series gravity bombs. The new B61-12 bombs are currently being prioritized for replacing aging nuclear assets both in the continental United States and at NATO bases. Given the strategic priority placed on homeland defense, allocating a portion of this limited arsenal for deployment to select allies, including South Korea, remains a significant challenge.

c. Feasibility and Precedents for “Flexible Redeployment”

Given the aforementioned constraints, the United States is more likely to adopt a strategy of flexible redeployment rather than permanent deployment of tactical nuclear weapons. This operational concept does not involve the permanent stationing of nuclear forces in a specific location but instead emphasizes the ability to deploy them quickly and temporarily in times of crisis. Two recent cases merit particular attention in this context.

The first is the case of the U.S. Air Force base at Lakenheath, United Kingdom. The United States withdrew all tactical nuclear weapons from Lakenheath in 2008 but has since begun modernizing nuclear-related facilities in response to the 2022 Russia–Ukraine war. Historically, the Lakenheath base stored approximately 110 B61 gravity bombs across 33 hardened aircraft shelters (HAS). As of February 2025, modernization work has been completed on 22 of 28 HAS undergoing upgrades. The U.S. has also deployed approximately 54 F-35A fighter jets capable of delivering B61-12 bombs and has begun constructing new facilities dedicated to the so-called “surety mission” since 2023. The surety mission refers to the safeguarding and security of nuclear weapons within the U.S. Department of Defense and Department of Energy. In essence, instead of reintroducing permanently stationed tactical nuclear weapons, the United States has established the necessary infrastructure to enable emergency or temporary deployment at Lakenheath.

The second noteworthy case is the U.S. Air Force’s adoption of the Agile Combat Employment (ACE) concept. The core of ACE lies in force dispersion and mobility. Rather than concentrating forces at a fixed base, the strategy involves distributing and maneuvering them across various locations to exhaust enemy resources while increasing the survivability of allied assets. This concept is closely tied to ongoing U.S. efforts to modernize bases along the so-called “Second Island Chain,” including airfield extensions, runway construction, and hardened facilities at Tinian, Rota, Wake Island, and Kunsan. New THAAD deployments have also been made to Tinian and Rota. These cases suggest that under the second Trump administration, tactical nuclear deployment in the Indo-Pacific region may be pursued as part of a broader strategy to contain China—likely through the model of flexible redeployment described above.

3. Cost and Benefit Assessment of Flexible Redeployment

a. Cost Estimation

Based on the preceding analysis, this paper aims to assess both the initial costs and the strategic benefits that may be associated with implementing a flexible redeployment of U.S. tactical nuclear weapons. In terms of initial costs, it is estimated that flexibly redeploying between 1 and 20 B61-12 tactical nuclear bombs to Kunsan Air Base would require an expenditure of approximately KRW 773.3 billion to 924.3 billion (USD 567 million to 677.6 million). This estimate accounts for the combined costs of constructing and upgrading the following facilities and systems: Weapons Storage Vaults (WSV), Surety Barrier Systems, facilities for the deployment of F-35A squadrons, infrastructure related to Precision Guided Munitions (PGM) for the F-35A, Rapid Airfield Damage Recovery (RADR) systems, and dormitory accommodations for surety mission personnel (see Table 1).

Table 1. Estimated Costs for Flexible Redeployment at Kunsan Air Base, FY2024 (US$)

b. Feasibility Assessment

To evaluate the feasibility of flexible redeployment, it is useful to contextualize its cost relative to other defense expenditures. The estimated initial cost of flexible redeployment—KRW 773.3 billion to 924.3 billion (USD 567 million to 677.6 million)—would represent approximately 51% to 61% of South Korea’s defense cost-sharing contribution for 2026 (KRW 1.5192 trillion), around 10% to 11% of the projected total for the 12th Special Measures Agreement (SMA) from 2026 to 2030 (estimated at KRW 8.0634 trillion), and roughly 1% to 2% of South Korea’s total defense budget for 2025 (KRW 61.5878 trillion). Based on these reference points, the strategic cost-benefit of flexible redeployment can be summarized as follows.

[Cost-Benefit Aspects of Flexible Redeployment]

On the benefit side, flexible redeployment offers practical value in terms of deterrence against North Korea, strengthening extended deterrence, and enhancing alliance cohesion. Given the political and operational challenges surrounding permanent redeployment, flexible redeployment provides a more realistic “emergency deterrent” option. It also allows for greater crisis management flexibility, minimizing the risk of North Korean overreaction while preserving a credible and usable deterrent during heightened tensions. From the perspective of alliance management and extended deterrence, the establishment of related infrastructure could serve as a catalyst for the United States to operationalize its regional nuclear posture, while simultaneously advancing U.S.–ROK cooperation in areas such as extended deterrence consultation mechanisms, joint training, operational guidelines, and planning. This could help clarify the role of South Korean forces within the U.S. nuclear strategy, contribute to capability enhancement, reinforce the continuity of conventional-nuclear integration (CNI), and strengthen the “lock-in effect” of U.S. extended deterrence commitments.

Flexible redeployment is also advantageous in terms of political and operational feasibility. Among the various nuclear options South Korea could request from the United States, flexible redeployment entails the lowest military, political, economic, and social cost. For the U.S., it offers a way to mitigate the political and military risks associated with permanently stationing tactical nuclear weapons in the region—such as heightened tensions with China, budget constraints related to nuclear modernization, and domestic or international backlash against perceived violations of nonproliferation norms. For South Korea, it provides a way to strengthen deterrence and alliance cohesion while avoiding the political sensitivities surrounding permanent redeployment—such as the ultimate discarding of the 1992 Joint Declaration on the Denuclearization of the Korean Peninsula or backlash from civil society. It should be also noted that all the expenses at Lakenheath Air Base is supported by the U.S. Should U.S. assume the associated surety mission costs, the financial burden on South Korea could also be partially reduced. Lastly, should U.S. decide for USFK reduction, such emergency measure can be devised to reaffirm U.S.‘s unwavering commitment on the Korean Peninsula.

However, flexible redeployment is not without strategic constraints. As a component of broader U.S. efforts to balance against China in the region, it may provoke a strong response from Beijing, including economic retaliation or increased pressure on South Korea in the event of a Taiwan contingency. There is also a risk that North Korea may perceive flexible redeployment as a precursor to permanent deployment and react with aggressive countermeasures or miscalculations that escalate tensions. Militarily, some may question the added value of flexible redeployment given its overlap with the existing mechanism of nuclear umbrella - e.g. bomber deployments. Additionally, under Trump 2.0, there is a possibility that Washington will demand renegotiation and a significant increase in South Korea’s defense cost-sharing contribution—potentially raising it by at least 50%, given that the initial deployment cost equals approximately 51–61% of the current burden. Finally, if U.S. force posture in South Korea is under review, flexible redeployment could be used as justification for troop reductions or withdrawal.

[Cost-Benefit Comparison with Alternative Deterrence Options]

It is also necessary to compare the cost-effectiveness of flexible redeployment with that of alternative deterrence options—such as the missile defense system knowing n as “Golden Dome”—initiated through executive orders under the Trump administration (see Table 2).

Table 2. Comparison of Initial Costs: Flexible Redeployment vs. Alternative Deterrence Systems

In short, alternative deterrence options do not appear to offer clearer cost-effectiveness than flexible redeployment. For example, the PRSM (replacement for ATACMS) and the SM-6, with operational ranges of around 500km, overlap with South Korea’s indigenous Hyunmoo missile capability. Their non-nuclear nature also imposes inherent military limitations. Similarly, the Tomahawk missile—though with a range of 1,500km—remains a non-nuclear system and, if deployed on the Korean Peninsula, may send strategic signals to China comparable to those of flexible redeployment. Missile defense systems present clearer constraints across military, political, economic, and social dimensions. With a maximum budget of KRW 924.3 billion, South Korea could procure only about 1.2 PAC-3 batteries, each comprising 4–8 launchers and 16 PAC-3 MSE interceptors. A nationwide defense posture would require an additional 10 to 15 batteries. In the case of THAAD, the same budget would cover only 0.6 batteries. Given the current deployment in Seongju, at least three batteries are considered necessary for meaningful coverage of the peninsula. Moreover, further THAAD deployments would likely trigger a second wave of backlash from China, as well as significant domestic political and social costs related to site selection.

4. Policy Recommendations

a. Maintain a Strategic Wait-and-See Approach

As of 2025, the Trump administration has yet to finalize major strategic documents and Cabinet confirmations. The future direction of U.S. defense and alliance policy remains uncertain. Under these circumstances, South Korea should refrain from making specific requests such as the flexible redeployment of tactical nuclear weapons and instead adopt a “strategic wait-and-see” approach that allows for flexible engagement with the United States. President Trump, in his 2024 campaign pledges and early 2025 public speeches, has emphasized expanding missile defense systems and investing in advanced technologies, while simultaneously stating that “new nuclear weapons are unnecessary,” hinting at a potential slow-down in the U.S. nuclear modernization. These positions also imply a reduced U.S. commitment to overseas engagement and the potential for shifting greater responsibility onto allies. South Korea should focus on alliance management, continue to underscore the importance of deterrence against North Korea and ROK-U.S. alliance cohesion, and maintain an open negotiation posture that signals flexibility until the United States clarifies its alliance and North Korea policy.

b. Respond to U.S. Expectations for a Greater Role vis-à-vis China (Reassessing the China Threat)

Strategic competition between the United States and China is expected to continue under a second Trump administration, and pressure on South Korea to expand its role in relation to China is also likely to persist. South Korea should continue declaratory and conceptual responses to U.S. expectations—such as progressively expanding its language on the Taiwan Strait and South China Sea in joint U.S.-ROK-Japan statements. In parallel, South Korea should assess, referencing cases such as the fully U.S.-funded surety mission at Lakenheath Air Base in the U.K., how flexible redeployment on the Korean Peninsula could offer strategic complementarity to the U.S. Indo-Pacific posture—while ensuring such measures remain within acceptable cost and political thresholds from Seoul’s perspective.

c. Considerations for Flexible Redeployment

Flexible redeployment holds strategic value as an emergency deterrence and assurance mechanism for the alliance. South Korea should treat flexible redeployment as a supplementary measure to bolster deterrence against North Korea and to reinforce the credibility of extended deterrence.

Seoul should strengthen monitoring of U.S.‘ potential redeployment in the Indo-Pacific. Given the Korean Peninsula’s geographical proximity to both North Korea and China, it is highly likely that the United States would first pursue tactical nuclear deployments or flexible redeployment initiatives outside the Peninsula within the broader Indo-Pacific region. In anticipation of such scenarios, South Korea must closely monitor these developments and be prepared to engage in proactive negotiations to ensure that comparable deployments are considered for the Korean Peninsula as well.

Last but not least, to prevent flexible redeployment from triggering unintended escalation, the strategic appropriateness of the term "flexible redeployment" itself should be reexamined. It may be beneficial for the allies to consult on adopting a nuanced term. Additionally, after base modernization is completed, the question of whether actual deployment will occur should be managed under a policy of strategic ambiguity—specifically through the application of the “Neither Confirm Nor Deny” (NCND) principle regarding nuclear weapon presence.