South Korea's lingering nuclear debate comes into focus

President Lee Jae Myung delivers his inauguration address, 4 June 2025 (photo via the Republic of Korea Presidential Office)

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The political pause in South Korea ended with the recent election of President Lee Jae Myung, Democratic Party of Korea. President Lee began the arduous task of binding a politically divided South Korea on 4 June 2025 with his inaugural address, vowing, “From now on, there are no progressive issues or conservative issues–only the people’s issues and Korea’s issues.” He stressed the importance of resolving long-standing problems and building a stronger and more resilient South Korea. Among the “people’s issues” that Lee cited is the enduring presence of a nuclear-capable North Korea. 

As the new South Korean administration contemplates its inter-Korean policies, the nuclear question will continue to come into focus–not only regarding North Korea’s ongoing nuclear and missile advancement, but also whether South Korea should have them, too. The South Korean approach to this issue will have implications that extend far beyond the Korean Peninsula, making it important for observers to understand the background, debates, and potential outcomes going forward.

Setting the scene

Since taking over control of the North Korean government in 2011, Kim Jong Un has employed different policy approaches than his predecessors when it comes to his country’s nuclear program and position towards inter-Korean engagement. Unlike Kim Jong Il, who was willing to barter elements of his nuclear program, the Kim Jong Un regime has doubled down, substantially growing the size and capability of North Korea’s nuclear armaments and successfully deflecting the international community’s efforts to compel denuclearization. Further, his government recently closed the book on inter-Korean reunification, eschewing any form of engagement with South Korea, a point firmly reiterated in a recent statement attributed to Kim Jong Un’s sister, Kim Yo Jong. While President Lee’s plan for “peaceful co-existence” with North Korea is still taking shape, past approaches such as complete denuclearization and reunification are becoming increasingly unrealistic given these benchmark policy positions from the Kim Jong Un regime.  

Meanwhile, the return of the Donald Trump administration has generated unease among U.S. allies. The return of “America First” policies has been accompanied by the White House’s willingness to impose economic pressure on both allies and adversaries through high tariffs, along with calls for increased defense spending and “burden sharing” in security relationships. Fears of abandonment have amplified with the Trump administration’s coercive diplomacy with partners and positive rhetoric towards authoritarian leaders, including Kim Jong Un. For South Korea, President Trump has been vocal about expectations to shoulder more of the financial costs and of his desire for a reduction in U.S troops on the Korean Peninsula. For a country whose defense security is so closely tied to its sole alliance with the United States, the fears of American retrenchment in peacetime or abandonment in a time of need drive arguments for greater autonomy.  This will continue to be true as the new Lee Jae Myung administration debates the nuclear question. 

The Trouble with Denuclearization

Since the 1990s, South Korea’s primary policy approach to addressing nuclear tensions has been to pursue the complete denuclearization of  North Korea while maintaining defense security under the United States nuclear umbrella. The Joint Declaration of North and South Korea on the Denuclearization of the Korean Peninsula went into effect in February of 1992 in which both sides agreed to (1) no testing, manufacturing, production, receipt, storage, possession, deployment, or use of nuclear weapons; (2) neither party would possess nuclear facilities for uranium enrichment or reprocessing; and (3) the use of nuclear energy would be limited solely to peaceful purposes. 

This policy approach has not achieved the desired denuclearization results as North Korea has defied adherence to all conditions of the Joint Declaration. Through North Korea’s single-minded focus on achieving security through nuclear power, it has achieved becoming a nuclear dyad with land and sea-based capabilities, including short-range, medium-range, intermediate-range, and intercontinental ballistic missiles (ICBMs), and a well-developed system of launch platforms, including ground, vehicle, rail, and submarine-based launch platforms. Estimates indicate they presently have 50 warheads in their nuclear arsenal with enough fissile material for up to 90 warheads, along with two confirmed nuclear enrichment facilities. 

Kim Jong Un inspects a uranium enrichment facility in an undisclosed location, September 2024 (photo via Korean Central News Agency)

North Korea has also signaled its departure from denuclearization commitments by cementing its nuclear posture through domestic legal reforms. In 2022, they passed legislation identifying themselves as a nuclear-armed state, with the right to use preemptive nuclear force in response to perceived threats. A year later, they enshrined their nuclear status through a constitutional amendment allowing for the rapid development of nuclear weapons. By embedding their position to develop and use nuclear force in its constitution, the North Korean government has effectively cut off any hope for denuclearization in the near future and elevated nuclear policies and practices to the level of strategic doctrine. 

The current policy trajectory of denuclearization intensifies the risk of escalation between North and South Korea, partly because its entrenchment encourages reciprocal South Korean proliferation. While deterrence remains essential for maintaining security on the Korean Peninsula and in the broader region, an uncompromising stance on denuclearization—especially when paired with signals that could be interpreted as moving South Korea toward nuclear armament—risks inadvertently heightening tensions with North Korea by being perceived as a provocative threat. A hard-line approach on denuclearization runs counter to President Lee’s goal to open channels of dialogue with North Korea and restore inter-Korean relations, as diplomacy is a key component of his plan for stabilizing security on the Peninsula and achieving peaceful co-existence. 

Newly appointed Minister of Unification Chung Dong-young observes the Joint Security Area in Panmunjom immediately following his confirmation, 25 July 2025 (photo via the Ministry of Unification)

South Korea’s nuclear debate

The robustness of North Korea’s nuclear capabilities, coupled with the heightened concerns about the credibility of U.S. security guarantees, amplifies long-standing debates about whether the time has come for South Korea to develop its nuclear capabilities. Instead of the fundamental question of whether it is appropriate, discourse has shifted to how it might be possible, whether it is nuclear latency, strategic ambiguity, nuclear sharing, or the pursuit of overt nuclear weapons state status.

This is not the first time that such a debate has come into focus. Concerns over U.S. abandonment and a desire for strategic autonomy compelled the Park Chang-hee government to pursue a clandestine nuclear weapons program in the 1970s. This only stopped once the U.S. government discovered the effort and took deliberate steps to halt the program. Through a series of bilateral negotiations, the two governments found alternative means to ameliorate South Korean security concerns and reaffirm alliance commitments. 

The declassified cable drafted by the U.S. Embassy to warn about the ROK’s clandestine nuclear program, 3 March 1975 (via the U.S. National Archives and Records Administration)

Longitudinal polling is useful for showcasing that public support exists for an indigenous nuclear weapon program in South Korea. The data highlights that while public support has remained consistent, there are also no significant increases despite the expansion of North Korea’s nuclear capabilities. The Center for Strategic and International Studies analyzed data from 55 surveys spanning 13 years, between January 2010 and December 2023. Interestingly, the data does not reveal any correlation between public support and the increase in nuclear activity from North Korea. The results indicated 59% of the public favored the nuclear option between January 2010 to August 2017, and after the sixth North Korean nuclear testing in September 2017, public support only increased incrementally to 61%. It is important to note that public polling surveys tended to be brief and noncontextual (simply assessing whether persons were either supportive or non-supportive of South Korea going nuclear), which may overinflate public support.

Political support for an overt nuclear arsenal or nuclear latency exists on both sides of the political spectrum. Historically, it rests with President Lee's conservative opposition, as it is viewed as a more reliable nuclear deterrent option than U.S. extended deterrence and eliminates a major disparity in firepower between the North and South. Still, the desire for security autonomy and further decoupling from the United States has resulted in calls within the progressive camps to develop nuclear latency, preparatory work laying the foundation for a rapid transition to nuclear weapons production if security conditions deteriorate, otherwise known as breakout capability. With the ability to enrich or reprocess nuclear material,  nuclear latency strengthens deterrence while stopping short of stockpiling actual nuclear weapons.  While not as controversial as pursuit of an overt nuclear weapons program, it still introduces several problems for either conservatives or progressives, as it is currently prohibited under the 123 Agreement for Nuclear Cooperation with the United States, could damage the ROK-U.S. alliance without coordinated action, and risks being misinterpreted as a provocative action, inadvertently putting them and the region at greater risk for escalating conflict. 

Then-President Moon Jae-in oversees the successful launch of a submarine launched ballistic missile (SLBM) from a South Korean naval vessel, 15 September 2021 (promotional imagery from the Republic of Korea Presidential Office)

The ability to enrich or reprocess nuclear material is only one step involved in developing a fully functional nuclear arsenal, an endeavor requiring significant time and financial costs. Appropriate delivery systems, time for development and testing of warheads, and a sustainment and maintenance program are other requisite components. Additionally, South Korea would need to create the necessary command structure, policies, and doctrine to support a nuclear program, as well as break or renegotiate their positions on the Nuclear Nonproliferation Treaty and the North-South Joint Declaration on Denuclearization. The establishment of ROK Strategic Command, ROKSTRATCOM, in October 2024 opens a new avenue in ROK’s strategic defense infrastructure and combat potential. An independent command outside the ROK-U.S. alliance, ROKSTRATCOM’s focus is to integrate nuclear and conventional forces and develop warfighting capabilities across future domains such as space, cyber, and electromagnetic spectrum alongside the ROK-U.S. Nuclear Consultative Group. Its establishment creates space for the planning and negotiation of nuclear options in the future. 

Many argue that North and South Korea co-existing as nuclear adversaries may, in fact, create a sense of strategic stability that paradoxically encourages the occurrence of lower-level conflicts but prevents nuclear escalation due to their mutually assured destruction. On the other hand, if significant imbalances in stability and security exist between nuclear adversaries, the stabilizing effect of mutual deterrence may weaken, increasing the risk of full-scale conventional conflict and potential nuclear escalation. If South Korea were to reach nuclear parity with North Korea, it would run the risk of facing aggressive conventional warfare from North Korea despite the asymmetry between military forces. For instance, nuclear parity between India and Pakistan has not consistently prevented conflict involving the loss of life and the threat of greater escalation. While different from the conditions on the Korean Peninsula, there are similarities between Pakistan and North Korea’s pursuit of autonomy from their neighbors. Additionally, Pakistan and North Korea have both utilized the strategy of nuclear brinkmanship; that is, the use of nuclear capabilities in bargaining behaviors. 

The potential impact on inter-Korean relations

The Lee administration has not expressed any desire for indigenous nuclear weapons, ambiguous or overt, nor for a return of U.S. nuclear warheads through a nuclear sharing defense strategy. Instead, his defense security approach has thus far been firmly rooted in the alliance with the United States, extended deterrence, and a commitment to deepen trilateral security cooperation with the U.S. and Japan while simultaneously pursuing peaceful coexistence with North Korea. A final option that supports the notion of co-existence and keeps South Korea firmly on a non-nuclear path entails a reorientation away from demanding North Korea dismantle their nuclear program and instead accepts, for now, their de facto nuclear status. This recognition would open negotiations on containment and reduce pressure on Seoul to pursue nuclear options. Another move to improve relations is to accept North Korea’s proposed two-state solution, creating space to cooperate on economic and cultural issues and reducing the pressure on Pyongyang to further their partnership with Russia.      

By pursuing “co-existence” as opposed to “reunification,” the Lee administration is indicating the need for a different approach to inter-Korean relations to de-escalate tensions.  North Korea has signaled a significant shift in its relational approach with South Korea, one that reframes the traditional unification narrative. Kim publicly rejected the feasibility of reunification in December of 2023, and then altered their constitution in October of 2024 by removing all traces of reunification as a goal of North Korea. South Korea was then earmarked as a “hostile state,” and agencies and organizations focused on inter-Korean relations were dismantled or rebranded; e.g., renaming the National Reunification Institute to the DPRK Institute of Enemy State Studies. In an emblematic demonstration, North Korea blew up sections of the inter-Korean roads linking them to South Korea and demolished the Arch of Reunification, a monument symbolizing the goal of reunification. In response, the new Lee administration is contemplating how to reframe reunification efforts if it hopes to restart dialogue with Pyongyang, including possible renaming of its own ministries and organizations related to inter-Korean relations. 

Views on unification amongst South Koreans vary greatly by generation. Polling shows a higher support for unification among the war generation than the millennials, 73.6 percent compared to 46.5 percent. Additionally, millennials mainly supported unification as a mechanism for “alleviation of the threat of war,” while the war generations' primary motive is “ethnic kinship.” This distinction is important, as it raises the possibility that the younger generation may be more amenable to a two-state solution, specifically one centered around cooperation and stable co-existence, as opposed to pursuing pathways leading to two states as nuclear adversaries.  

Ultimately, circumstances have shown that the current approach for complete denuclearization of North Korea is no longer effective due to the expanded capability of the North’s program and decreasing support for reunification. The Lee administration could consider changing the focus from elimination to containment to create space for the negotiation of attainable goals on limits and use, which may decrease pressure within South Korea to pursue its own nuclear program. That debate will linger based on supporters from both the conservative and progressive sides, with few considering that the pursuit of nuclear parity could destabilize the Peninsula, potentially leading to increases in lower-level clashes that invariably escalate nuclear tensions and further erode relations between Seoul and Pyongyang.  Given these circumstances, if President Lee is truly aiming for peaceful co-existence between North and South Korea, this debate is one his administration must continue to manage.

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Jessica Earl is an international relations specialist focused on contributing to sustainable peace across deep divides. Her current research and analysis draw on her background in social welfare and disability advocacy, as well as her interest in understanding the conditions that prevent conflict and promote peace and security.

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