Four months after throwing the country into chaos with his declaration of martial law, on April 4, 2025, South Korean President Yoon Seok Yeol was removed from office. Now, a new presidential election is set to take place in 60 days. Although a deep scar has been left, South Koreans now have an opportunity to close one chapter and open a new one.
The incoming administration, regardless of who leads it, will confront significant challenges, from deep social divisions and democratic backsliding to economic instability. However, one of the most pressing concerns will be addressing North Korea’s nuclear threats amid growing uncertainty over U.S. security commitments under the second Trump administration. Support for nuclear armament in South Korea is intensifying, which raises a critical question: Will South Korea’s next administration pursue its own nuclear deterrent?
Historically, it has been South Korean conservatives who have openly supported nuclear armament. Given the progressive historical emphasis on reconciliation with North Korea by the Democratic Party of Korea (DPK), some may expect Seoul’s nuclear ambitions to fade, at least over the next five-year presidential term. However, South Korean progressives may not be as anti-nuclear as they appear. Previous progressive leaders have engaged in “nuclear hedging”—keeping the nuclear option open by developing capabilities for rapid acquisition if needed while stopping short of outright nuclear armament. Meanwhile, all conservative presidential hopefuls support outright either nuclear armament or nuclear hedging. Hence, Seoul’s nuclear ambitions will persist, and Washington needs to pay close attention.
Growing Calls for Nuclear Armament
Calls for nuclear armament had already been rising in South Korea before Trump’s return to office. Public opinion polls have consistently shown that a majority of South Koreans—often over 70 percent—support the development of indigenous nuclear weapons. While support for nuclear armament remains significantly lower among elites, as indicated by a Center for Strategic and International Studies survey, a growing number of influential politicians—particularly conservatives, including President Yoon Suk Yeol and other prominent politicians—have openly endorsed the idea. Others advocate nuclear hedging. Last year, a member of the ruling conservative People Power Party (PPP), Yoo Yong-won, launched a National Assembly initiative known as the Mugunghwa Forum, aimed at galvanizing support for acquiring the capability to quickly go nuclear for nuclear hedging purposes. Several conservative politicians have joined the initiative.
Trump’s return to office further intensified South Koreans’ support for nuclear armament. Just days into his second term, President Trump and his secretaries of defense and state referred to North Korea as a “nuclear power,” potentially implying U.S. acceptance of North Korea as a nuclear-armed state. In addition, Trump said he would “reach out” to Kim Jong-un, raising speculation that Washington might pursue arms control with North Korea instead of denuclearization, leaving South Korea vulnerable to nuclear threats. In a poll conducted shortly thereafter, 74 percent of South Korean respondents said South Korea should acquire nuclear weapons if the international community recognizes North Korea as a nuclear weapons state. Such sentiment is shared by several presidential hopefuls. The majority of conservative candidates—Kim Moon-soo, Oh Se-hoon, and Hong Joon-pyo—support nuclear armament. Han Dong-hoon, another presidential hopeful who served as the leader of PPP, advocates nuclear hedging.
Seoul’s Nuclear Ambitions over the Next Five Years
So far, support for nuclear armament has been primarily driven by conservatives, who have viewed North Korea as an existential threat, prioritizing military strength and deterrence. Now, progressive leader Lee Jae-myung, who narrowly lost to Yoon in the last presidential election by 0.7 percent, is leading the field with 34 percent support, while conservative hopefuls trail far behind. Traditionally, progressives have prioritized peaceful coexistence and engagement with North Korea, advocating for diplomatic dialogue, economic cooperation, and tension reduction on the Korean Peninsula. Most progressives have voiced dissent against outright nuclear armament, with many opposing even the use of nuclear technology for peaceful purposes.
However, it would be a mistake to think that progressives lack ambitions for nuclear weapons altogether. Though stopping short of outright nuclear armament, they have also pursued nuclear hedging to ensure Korea has the capability to rapidly develop nuclear weapons if the need arises in the future. To that end, they have sought to acquire the ability to produce nuclear fissile materials via enrichment or reprocessing, the biggest hurdle to acquiring nuclear weapons.
The pursuit of nuclear-powered submarines by former progressive Presidents Roh Moo-hyun and Moon Jae-in seems to be driven by their ambitions for nuclear hedging. This pursuit goes back to June 2003, when President Roh executed a plan to build nuclear-powered submarines. To produce fuel for the submarines’ naval propulsion, the ability to enrich uranium was required. However, this plan probably served two goals, since a country with enrichment capability can also enrich uranium to weapons-grade levels without significant difficulty. The fact that Roh launched this plan less than five months after North Korea’s withdrawal from the Non-Proliferation Treaty (NPT) supports the possibility that his ulterior motive was to acquire uranium enrichment capability in part to enable the future development of nuclear weapons. Ultimately, Roh had to abandon this plan in 2004 amid rising suspicion of South Korea’s nuclear ambitions after the International Atomic Energy Agency (IAEA) discovered that South Korean scientists had previously conducted an unauthorized enrichment experiment.
President Moon Jae-in revived Roh’s plan when he came into office in 2017. He pursued the development of nuclear-powered submarines ostensibly as a means to counter North Korea’s submarine-launched ballistic missile capacity, demonstrated in 2016. As South Korea’s bilateral nuclear cooperation agreement with the United States, also known as the 123 Agreement, prohibits the country from enriching or reprocessing nuclear fissile materials without U.S. consent, Moon sought to persuade the United States to revise the treaty to allow for nuclear-powered submarine development, but was ultimately unsuccessful during his tenure.
Why Are Progressives Motivated to Seek Nuclear Hedging?
Some may find it puzzling that progressives, who are generally believed to be the doves, would pursue the capability to build nuclear weapons. However, their rationale for nuclear pursuit differs somewhat from conservatives, who advocate for nuclear armament primarily in response to North Korea’s growing nuclear threat. Though countering North Korea’s nuclear threats is still part of the calculations, the progressives’ rationale is strongly driven by their desire for autonomous self-defense—seeking strategic independence from the United States. This explains the seemingly contradictory stance of the progressives, who I have described elsewhere as “hawkish doves.”
The progressives’ push to reclaim wartime operational control (OPCON) reflects their emphasis on autonomous self-defense. South Korea transferred OPCON, the authority to direct military forces in the planning and execution of operations, to the United States during the Korean War. Although it regained peacetime OPCON after the Cold War, the United States still retains control during wartime. Roh Moo-hyun lamented South Korea’s lack of full military control and rebuked military leaders who opposed OPCON transfer due to their concerns over military readiness and competence, declaring, “Shame on you.” In 2007, Roh and President George W. Bush agreed to transfer OPCON to South Korea by April 2012. However, the timeline was postponed to 2014 under Roh’s conservative successor, Lee Myung-bak, and indefinitely under President Park Geun-hye. Reversing this trend, Moon Jae-in vowed to reclaim OPCON during his tenure, though he failed to do so. For progressives, OPCON transfer is essential to restoring full national sovereignty and self-defense, an unresolved issue after decades of foreign intervention. The nuclear option, as the ultimate tool for self-defense, undoubtedly holds strong appeal for progressives.
If elected president, Lee Jae-myung will likely continue down this path and pursue nuclear hedging, judging from his policy platform during the 2021 presidential campaign. At the time, he pledged to advance the development of nuclear-powered submarines capable of extended underwater operations, enhancing intelligence and surveillance to counter North Korea’s nuclear threats. He also vowed to reclaim wartime operational control from the United States, emphasizing: “Among the core elements of sovereignty, military sovereignty is the most fundamental, and within that, operational control is the key issue. The fact that we have entrusted this to another country is, in reality, beyond common sense and an exceptional situation.” He further criticized the objection to reclaiming OPCON, stating: “I truly cannot understand the belief that without the U.S., our national defense would be impossible. It is astonishing to hear that many in the military think this way,” echoing Roh Moo-hyun’s rebuke of military generals. More recently, the DPK is reportedly considering revising the 123 Agreement as part of its campaign platform to permit enrichment for naval propulsion and reprocessing for spent-fuel management. Taken together, these positions suggest that Lee would likely pursue nuclear hedging not only to counter North Korea but also to bolster South Korea’s autonomy from the United States.
Washington Must Take Notice
Of course, anything can happen in South Korean politics. But regardless of who wins the election, the next South Korean leader will either be an explicit advocate of nuclear armament or a tacit supporter of nuclear hedging. Thus, Seoul’s nuclear ambitions will remain a given for the next five years and beyond. Therefore, the new administration in Washington must establish a clear policy to address this issue. Both President Trump and Under Secretary of Defense for Policy nominee Elbridge Colby have hinted at a willingness to tolerate South Korea’s nuclear armament—a stance that may be pragmatic, if not inevitable. However, whatever course Washington may take, it must ensure that its decision is a well-considered policy based on comprehensive analyses of secondary and tertiary consequences.
Lami Kim is a professor at the Daniel K. Inouye Asia-Pacific Center for Security Studies, a U.S. Department of Defense Institute based in Hawaii. The views expressed are those of the author and do not necessarily reflect the official policy or position of the U.S. Department of Defense or the U.S. Government.
