South Korea's Nuclear Dilemma: Seoul Weighs Armament as Deterrence Frays

The debate over whether South Korea should acquire its own nuclear arsenal has moved from the fringes of academic discourse to the center of national policy discussions. With public support for nuclear armament hovering near 70 percent and a growing perception that the United States is an unreliable security guarantor, Seoul finds itself confronting a strategic choice unprecedented in its modern history. The confluence of North Korea's expanding nuclear capabilities, its deepening military alliance with Russia, and questions about the credibility of the American extended deterrence commitment have created a perfect storm of strategic anxiety.

The Strategic Dilemma: A Guarantor in Question

The structure of global security has been changing in profound ways, and South Korea sits at the epicenter of these shifts. A major conventional war in Europe has demonstrated that nuclear deterrence does not necessarily prevent large-scale armed conflict, a phenomenon that arms control expert Rose Goettemoeller has termed "The Strange Defeat of Nuclear Deterrence." This paradox has the unsettling consequence that regional powers feel an increasing need to acquire nuclear weapons precisely because the existing nuclear order appears unable to prevent war.

For South Korea, the dilemma is acute. North Korea continues to expand its nuclear arsenal and has formalized a significant alliance with Russia, even as Pyongyang has renounced unification and constitutionally designated South Korea as its primary enemy. The continental United States is now within reach of North Korean ballistic missiles, raising fundamental questions about whether Washington would risk American cities to defend Seoul. This is not merely a theoretical concern; it is a question that South Koreans are asking with increasing urgency, and the answers they receive from Washington will shape the future of the alliance.

The Chun In-bum Proposal: A Dual-Key System for the Peninsula

On July 27, retired Lieutenant General Chun In-bum published a sophisticated proposal in the Korea Times that has since dominated strategic discussions in Seoul. Chun's plan envisions South Korea acquiring a nuclear arsenal that Seoul would own but which would be embedded in an integrated deterrence network with the United States. The arrangement would resemble the deployments of nuclear weapons in Europe during the early Cold War, featuring a dual-key system requiring the consent of both the host country and the United States for any launch.

Chun himself acknowledged that this proposal raises significant issues regarding the Nuclear Non-Proliferation Treaty (NPT), verification protocols, and decision-making procedures. The fundamental problem, however, is that the dual-key approach does not resolve the underlying dilemma of "entrapment or abandonment." If the United States maintains escalation control, this amounts to a veto in a different form. If South Korea had independent launch authority, then Washington could find itself embroiled in a nuclear conflict against its will. The proposal's elegance on paper does not translate into operational clarity in practice.

Public Opinion: Widespread Support, Nuanced Preferences

The public mood in South Korea reflects this strategic anxiety. A survey conducted by the East Asia Institute (EAI) and Hankook Research on July 20-21 found that 69.1 percent of respondents support South Korea possessing nuclear weapons if the North Korean nuclear threat persists, up 1.6 percentage points from 67.5 percent last year. Those opposed accounted for only 19.6 percent. Support for nuclear armament has remained at or above the mid-60 percent range in recent years, with notable fluctuations: 69.6 percent in 2022, dropping to 58.5 percent in 2023 after the Washington Declaration strengthened extended deterrence commitments, then rebounding to 71.4 percent in 2024 as North Korea-Russia ties deepened.

A separate survey by the Reform Institute, the think tank arm of the Reform Party, conducted on August 11, found that 75.1 percent of respondents supported the general proposition of redeploying US tactical nuclear weapons to South Korea. Support was particularly high among younger respondents, with 88.4 percent of those in their 20s and 86.3 percent of those in their 30s backing redeployment. This suggests that concerns about nuclear deterrence are not confined to older or traditionally conservative voters but have permeated the younger generation that will shape South Korea's future.

However, the Reform Institute survey also revealed important nuances. When asked to identify the single highest priority for addressing the North Korean nuclear threat, 36.3 percent chose strengthening the US nuclear umbrella and South Korea's missile defense capabilities. This exceeded support for developing an indigenous nuclear capability (26.9 percent), redeploying US tactical nuclear weapons (16.9 percent), or pursuing diplomacy with North Korea (16.8 percent). South Koreans may be increasingly open to nuclear options, but a plurality still prefer strengthening deterrence through the alliance rather than pursuing an independent arsenal.

The Alliance Bind: Entrapment, Abandonment, and Credibility

The central problem for extended deterrence is credibility. The Reform Institute survey found that respondents were almost evenly divided on whether the United States would actually retaliate with nuclear weapons if North Korea used a nuclear weapon against South Korea, even if doing so exposed the American homeland to retaliation. Only 41.8 percent believed Washington would do so, while 41.7 percent did not. This near-perfect split encapsulates the crisis of confidence at the heart of the alliance.

The practical difficulties of nuclear sharing arrangements are illustrated by the long-running negotiations over the transfer of wartime operational control (OPCON) over ROK forces, a process that has dragged on for two decades. OPCON transition requires highly coordinated intelligence and communication systems, interoperability, training, and finely tuned relations between South Korean and American commanders. Nuclear decision-making would be even more complex, involving the US president directly, with decision times potentially measured in minutes given the geography of the Korean Peninsula. The requirement for reassurance against unauthorized launch must be balanced against the need for credible retaliation in the eyes of the adversary.

The political environment has further complicated these calculations. The cancellation of joint military exercises during the previous US administration raised questions about Washington's commitment to the alliance, while President Lee Jae-myung's push for greater military independence has added a new dimension to the debate. These developments have occurred against the backdrop of North Korea's accelerating modernization of conventional forces and its 2022 enactment of a nuclear forces policy law establishing a legal basis for the pre-emptive use of nuclear weapons under certain conditions.

Regional Consequences: China, Russia, and the Proliferation Cascade

A South Korean nuclear arsenal, even if embedded in an alliance command structure, would have profound regional consequences. Beijing would likely consider such a capability a direct threat to its own security. The precedent of the THAAD deployment in 2016 is instructive: the decision to deploy the missile defense system provoked a major reaction from China, including the imposition of political and economic costs. A South Korean nuclear arsenal would likely provoke an even more serious response, potentially including economic sanctions, increased military deployments, and the retargeting of Chinese nuclear forces against South Korea.

The impact on Russia would be equally significant. Moscow could be encouraged to enhance its support of North Korea and its sharing of technology with respect to nuclear delivery and control systems. This would create a dangerous feedback loop, accelerating North Korea's efforts to develop a secure nuclear capability that could strike the United States. A South Korean nuclear program could also rekindle the nuclear debate in Japan, potentially triggering a broader proliferation cascade in Northeast Asia.

The NPT Constraint: Legal and Diplomatic Barriers

The legal obstacles to a South Korean nuclear program are substantial. Leaving the NPT is not merely a reputational or technical issue. Under Article I of the treaty, the United States would be constrained from transferring possession or control over nuclear weapons to South Korea or providing any nuclear assistance. The civil nuclear technology cooperation between the two countries, governed by the "123 Agreement" of 2015, would be in jeopardy. South Korea would face international isolation, severe strains on the alliance, and a more hostile international security environment.

The narrative dimension is equally important. A democratic South Korea acting in conformity with international law has long been contrasted with the rogue North Korean state. Abandoning NPT commitments would fundamentally alter this narrative, undermining South Korea's moral authority and its position as a responsible member of the international community. This is a cost that policy elites in Seoul understand acutely, even as public opinion pushes toward nuclear options.

Paths Forward: Consultation, Integration, and the NCG

There is little immediate prospect that proposals for an indigenous South Korean nuclear arsenal can become policy. But this does not mean there are no paths forward. The integration of US nuclear weapons and conventional forces into operational planning, nuclear consultation, integration of early warning and intelligence, missile defense, and various signals regarding the commitment to extended deterrence could strengthen stability without crossing the nuclear threshold.

The US-ROK Nuclear Consultative Group (NCG) was established precisely to deepen South Korean participation in discussions over nuclear deterrence and planning. As Washington reviews its nuclear employment guidance, the NCG cannot simply become a mechanism through which Seoul is informed after major decisions have already been made. South Korea does not need access to American nuclear operational plans, but it does need meaningful consultation on changes that directly affect the credibility and structure of extended deterrence on the peninsula.

The United States already possesses the W76-2 low-yield submarine-launched ballistic missile warhead and is developing the nuclear-armed sea-launched cruise missile. These capabilities can provide regional nuclear options without permanently stationing nuclear weapons on South Korean territory. However, a nuclear capability meant to strengthen extended deterrence cannot be fully credible if allies expect it to disappear every time politics change in Washington. Whatever posture the United States ultimately adopts in Northeast Asia needs broader bipartisan support, and so does South Korea's own approach.

The fundamental dilemma remains unresolved. If South Korea feels it can no longer rely on the United States, it could develop its own nuclear deterrent, but it would have to face consequences that may include international isolation, severe strains on the alliance, and a more hostile international security environment. The path forward lies not in dramatic nuclear breakthroughs but in the patient, difficult work of strengthening the credibility of extended deterrence through institutional mechanisms like the NCG, while maintaining the legal and normative frameworks that have served the alliance for decades.

This article was produced with AI-assisted research and editorial support. Sources: The Diplomat, Korea JoongAng Daily, Asia Times/Pacific Forum, The Guardian.