The Evolution of South Korea’s Nuclear Weapons Policy Debate

South Korea’s shifting domestic consensus regarding nuclear weapons, North Korea’s expansion of its nuclear doctrine to include offensive capabilities, growing South Korean public threat perceptions of North Korea and China, and expectations for South Korea’s global role and status are all factors that contribute to South Korea’s policy debate on the possibility of acquiring nuclear weapons. These developments require serious consideration from U.S. policymakers and security analysts due to the regional implications of a potentially nuclear South Korea.

While South Korean public support toward nuclear weapons acquisition has ranged between 50 and 70 percent throughout the past decade, recent public opinion polls indicate that public support for nuclear weapons has surpassed 70 percent. The Chicago Council on Global Affairs found that 71 percent of South Korean respondents supported the development of a domestic nuclear weapons program due to the need to defend South Korea from threats other than North Korea (39 percent), increase the prestige of South Korea to the international community (26 percent), and counter the growing threat from North Korea (23 percent). This trend suggests that the South Korean public remains dissatisfied with efforts to date to maintain the status quo and reaffirm U.S. extended deterrence through the nuclear umbrella.

An active and ongoing debate both within South Korea and internationally considers various South Korean options regarding nuclear weapons and their implications. On the one hand, numerous editorials and politicians have argued that nuclear weapons are necessary for a South Korea facing an increasingly uncertain region surrounded by nuclear neighbors. On the other hand, various experts maintain that nuclear weapons will only bring about limited benefits for South Korea and will instead lead to significant costs and greater instability on the Korean Peninsula. The primary options are discussed in greater detail below.

Strengthening Existing Mechanisms in Coordination With the United States

The most consistently advocated option since North Korea conducted its first nuclear test in 2006 has been the strengthening of extended deterrence mechanisms and South Korean defense capabilities that support existing U.S. security pledges. The incumbent Yoon Suk-yeol administration has thus far pursued this policy, as shown in the May 2022 U.S.-South Korea Leaders’ Joint Statement. Efforts to strengthen existing deterrence mechanisms include the revival of the bilateral Extended Deterrence Strategy and Consultation Group (EDSCG), regularization and expansion of joint military exercises, and reaffirmation of trilateral U.S.-South Korea-Japan security cooperation in response to North Korean nuclear and missile threats.

In addition to strengthening extended deterrence efforts within the alliance, there is also support for embedding U.S.-led extended deterrence in regional frameworks. Chairman of the Sejong Institute Moon Chung-in, who previously served as special advisor to South Korean President Moon Jae-in, argues that the primary focus of South Korea’s geopolitical orientation that best serves the country’s national interest and the U.S.-South Korea alliance should be to prevent a regional arms race. To do so, scholars have recommended the establishment of a multilateral consultative group designed to coordinate and strengthen extended deterrence in the region. One such proposal involves the establishment of an Asian Nuclear Planning Group, mirroring the format of the NATO Nuclear Planning Group, that would provide a platform for South Korea, Japan, and Australia to discuss policies regarding U.S. nuclear forces and the U.S. nuclear planning process. The expansion of the EDSCG framework and inclusion of South Korea in multilateral nuclear consultations would both strengthen U.S. extended deterrence and increase transparency among alliance partners regarding U.S. nuclear weapons policy, all without the need for nuclear weapons to be present in South Korea.

Furthermore, both progressive and conservative administrations have advocated for South Korea to strengthen its conventional defense and missile capabilities to better deter and respond to North Korean provocations without nuclear weapons. In September of 2021, South Korea became the first non-nuclear country to acquire SLBM capabilities, and South Korea’s Ministry of National Defense (MND) released its 2022-2026 mid-term defense plan to invest 106.7 trillion won (roughly 81 billion USD) toward strengthening defense capabilities and advanced ballistic missiles. Under President Yoon, the MND has announced the establishment of a strategic command to oversee its “three-axis” defense system, which consists of the Korea Massive Punishment and Retaliation operational plan, the Kill Chain preemptive strike platform, and the Korea Air and Missile Defense system, to more effectively respond to the threat posed by North Korea.

However, despite efforts to bolster trust in U.S. security guarantees and the strengthening of South Korea’s conventional capabilities, the nuclear imbalance between the two Koreas remains. The concept of a “double asymmetry of power” – asymmetry at both the conventional and nuclear levels – has led to concerns that neither country perceives its security as being guaranteed, thereby feeding redoubled efforts to enhance military capabilities for purposes of deterrence.

Redeployment of Tactical Nuclear Weapons

In the decade between North Korea’s first nuclear test and the recent 2018-2019 summitry period of heightened diplomacy with North Korea, South Korean policymakers have debated whether the United States should redeploy tactical nuclear weapons to South Korea. The United States had previously stationed tactical nuclear weapons, or non-strategic nuclear weapons, in South Korea between 1958 and 1991 to counter a potential renewed invasion by North Korea. At its height, the U.S. nuclear arsenal in South Korea comprised eight weapons systems consisting of 950 nuclear warheads. Since the United States withdrew its nuclear weapons due to U.S. President George H.W. Bush’s global initiative that removed most overseas U.S. tactical nuclear weapons, there have been periodic South Korean calls for their redeployment that have intensified in response to North Korea’s steady progress in nuclear development. The debate reached new heights in 2017 when the then-opposition party Liberty Korea Party (LKP) led a nationwide campaign – even sending a delegation to the United States – to consolidate support for redeployment amid the growing North Korean nuclear threat, heightened tensions on the Korean Peninsula, and low prospects for denuclearization. Although such momentum for the redeployment option has since subsided, calls for the United States to return tactical nuclear weapons remain a part of the South Korean discussion.

Those who advocate for the redeployment of nuclear weapons argue that it is necessary for achieving a “balance of terror” on the Korean Peninsula, considerably shortening the response time to a potential North Korean nuclear attack, and utilizing the weapons as leverage in inter-Korean negotiations. In 2013, during the Carnegie International Nuclear Policy Conference, then member of the National Assembly Chung Mong-joon recommended that U.S. tactical nuclear weapons be reintroduced and for South Korea to be given leeway as a law-abiding country facing a rogue nuclear neighbor to withdraw from the Nuclear Nonproliferation Treaty (NPT), noting that reinforcing conventional capabilities is insufficient to prevent a war on the Korean Peninsula. During the conservative primary race leading up to the 2022 presidential election, candidate Hong Joon-pyo argued that due to North Korea’s advancing missile and nuclear capabilities, South Korea should not blindly trust the U.S. nuclear umbrella or the NPT and should instead request the redeployment of nuclear weapons to South Korea. “A nuke for a nuke” has become the guiding principle for those who argue that only the presence of nuclear weapons in South Korea would ensure the country’s national defense and bolster its negotiating position against North Korea. 

However, opponents note that reintroducing nuclear weapons to South Korea would openly violate the principle of denuclearization outlined in the 1992 Joint Declaration on the Denuclearization of the Korean Peninsula, which has been upheld by successive South Korean governments. When the LKP announced “the redeployment of tactical nuclear weapons” as a party platform in August of 2017, the Moon administration strongly condemned the position, noting that it would have negative consequences by weakening the grounds for denuclearization of the Korean Peninsula and could potentially lead to a nuclear arms race in Northeast Asia. Furthermore, opponents argued that “irresponsible nuclear populism” would do little to curb North Korea’s nuclear program and might return the Korean Peninsula to a pre-1991 danger zone for nuclear war. At that time, the Obama administration stated that the United States had no plan or intention to redeploy tactical nuclear weapons to the peninsula, believing them to be “unnecessary for the defense of South Korea.”

Nuclear Sharing Agreement

In 2019, following the abrupt end to the Hanoi summit and the release of a National Defense University report arguing for a NATO-style nuclear sharing agreement between the United States and its Indo-Pacific allies, public debate over nuclear weapons was reinvigorated over the idea of a U.S.-South Korea nuclear sharing agreement. In the case of the NATO agreement, U.S. B61 nuclear weapons are stationed in allied countries across Europe but remain under the control and custody of the United States. NATO has emphasized that the agreement is “not the sharing of nuclear weapons,” but rather the sharing of NATO’s extended deterrence mission and related responsibilities. The debate over a nuclear sharing agreement has gained additional attention since the September 2021 announcement of AUKUS, a trilateral U.S.-United Kingdom-Australia security pact that supports Australia’s acquisition of nuclear-powered submarines.

Proponents of a nuclear sharing agreement believe that such an arrangement would allow South Korea to assume a degree of control over U.S. nuclear weapons by being granted the right to utilize U.S. nuclear assets located outside the Korean Peninsula. A nuclear sharing agreement is viewed as a realistic alternative to independent nuclear weapons acquisition as it does not require nuclear weapons to be present in South Korea, only for South Korean fighter jets to be modified to carry nuclear weapons. President Yoon himself advocated for the redeployment of tactical nuclear weapons and nuclear sharing between the United States and South Korea early in his presidential campaign, although he subsequently excluded such pledges from his campaign platform and has not raised the issue as president. However, as South Korea continues to advance fighter jet and submarine capabilities, the argument for a Korean-style nuclear sharing framework that provides U.S. nuclear capabilities and infrastructure is likely to recur.

Those opposed to a nuclear sharing agreement point primarily to technical misunderstandings related to the concept of nuclear sharing. Opponents point out that the NATO sharing agreements only allow for the sharing of NATO fighter planes rather than the sharing of rights to U.S. nuclear weapons, stating that South Korea gaining any level of control over U.S. nuclear weapons would directly violate its obligations under the NPT. As critics note, “nuclear sharing isn’t a thing” since the decision to deploy nuclear weapons would ultimately lie with the United States. Whether South Korea decides to pursue a nuclear sharing agreement mirroring the NATO agreement or pursue a unique South Korean arrangement, opponents caution that any agreement offering nuclear sharing would only serve to exacerbate the Korean Peninsula’s security dilemma by undermining South Korea’s negotiating position in pursuit of denuclearization.

South Korean Independent Acquisition

In recent years, support for South Korean independent acquisition of nuclear weapons has steadily grown. Those who question the reliability of the U.S. nuclear umbrella or anticipate the advent of a new nuclear era on the Korean Peninsula have begun to openly consider the possibility of South Korea going nuclear. Proponents argue that it is the only option for South Korea to directly possess and control the operations of nuclear weapons. However, U.S. support for independent South Korean acquisition of nuclear capabilities would require not only a fundamental reconsideration of the global nonproliferation regime, but also a careful assessment of the regional implications of allowing South Korea to go nuclear. Opponents note that South Korea’s withdrawal from the NPT with U.S. approval would both undermine U.S. credibility in upholding the principle of nonproliferation and encourage countries in a similar security dilemma to pursue proliferation outside of the NPT. Not only might the proliferation debate within Japan evolve in response to regional developments, but the risk of a North Korean or Chinese preventive strike to stop South Korea from acquiring a nuclear weapons program may also heighten the risk of a regional conflict that draws in nuclear-armed states.

Alongside the independent acquisition debate in South Korea, the U.S. discussion regarding response options has evolved. Recently, American and South Korean specialists have begun to argue for serious consideration of U.S. acquiescence to South Korean nuclear acquisition. One argument is that U.S. support for an independent South Korean nuclear arsenal may be the most effective option for saving a weakened U.S.-South Korea alliance that faces both credibility challenges and growing geopolitical pressures. However, security experts generally maintain that nuclear weapons are not an effective political or military tool against North Korea and China; rather, they would increase the risk of low-level conflict escalation due to the “stability-instability paradox.”

Conclusion

Given advancements in North Korean and Chinese nuclear capabilities, growing concern about the reliability of U.S. extended deterrence, and the growth of South Korean international stature and influence, the nuclear debate within South Korea continues to generate serious discussion. With the current low prospects for successful diplomacy toward and denuclearization of North Korea, the debate over South Korea acquiring nuclear capabilities is reentering mainstream discussions as public support for nuclear weapons increases alongside growing regional tensions. For the independent South Korean nuclear weapons option to remain as the last resort, the United States and South Korea should further reinforce the extended deterrence efforts outlined above. The United States and South Korea should use the upcoming EDSCG meeting as a means to enhance the credibility of extended deterrence and to respond to the trend of growing South Korean public support for nuclear acquisition.