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The pursuit of nuclear weapons in South Korea is an age-old debate that comes and goes with every cycle of contestation with North Korea. However, in the last few years, the call for South Korea to have nuclear weapons has increased, gathering greater support among the public and intellectuals alike. This shift is taking place amidst North Korea’s increasingly belligerent behaviour, the Russia-Ukraine war, and another critical factor, which is conspicuously part of all conversations. This new driver is the increasing distrust between South Korea and the United States.
The distrust was visible in Former President Joe Biden and South Korean President Yoon Suk Yeol’s diplomatic conversations in the initial years, culminating with the signing of the Washington Declaration in 2023, where both sides agreed to “commit to engage in deeper, cooperative decision-making on nuclear "deterrence". Nonetheless, the debate on the issue continues, gathering steam daily. Therefore, it is important to realistically assess the undercurrents shaping this debate, the prospects of South Korea’s nuclearisation, and the challenges that South Korea will likely face in its pursuit of nuclear weapons.
Pursuit of nuclear weapons and strategic rationale
South Korea’s desire for nuclear armament is not new. The traumatic fear of war has haunted Seoul since its establishment. In addition to South Korea’s experience of the Acheson Line in 1950, Seoul has regularly experienced security anxiety over time, such as the US administration’s attempts to withdraw the US Forces in Korea (USFK) from South Korea.
The possibility of abandonment has been at the core of South Korea’s security anxiety, regardless of its growth in soft and hard powers.
Since then, the possibility of abandonment has been at the core of South Korea’s security anxiety, regardless of its growth in soft and hard powers. Being a non-nuclear state, Koreans have had a fundamental but dormant question in the deepest corners of their mind: “Would the US sacrifice New York for Paris?” Such a doubt comes from the idea that Washington’s interests are served better when tensions are not escalated. In other words, a conventional weapon-based response would prevent the regional security situation from going out of control. It is thus reasonable to retaliate with conventional weapons instead of proportional nuclear retaliation, even if Pyongyang launches a nuclear strike on South Korea.
Additionally, political pressure on the US president will be too huge to respond with nukes in retaliation. This is the point where the president would face a dilemma: whether to put the US cities, innocent civilians, and worldwide US bases at risk or sacrifice them to defend an ally which is not a part of the US territory. Thus, Seoul became concerned about the expected problem, igniting public anger that South Korea, incapacitated by nuclear strikes, would be unable to retaliate properly as a non-nuclear state, and the US would prevent escalation by requesting Seoul to restrain counterstrikes.
Another strategic rationale comes from South Korea’s fatigue as a non-nuclear state. North Korea has a long history of pursuing nuclear capabilities since the 1960s, even before it initiated its nuclear programme around 1993. On the contrary, the US already withdrew all American tactical nuclear weapons from South Korea in 1991, with Seoul’s consent, and the joint declaration of the de-nuclearisation of the Korean Peninsula.
Extended deterrence is not reassuring enough to permanently prevent South Korea from going nuclear, and there are considerably few talks about the ironic duality of the non-proliferation regime.
Despite this nuclear imbalance in the Korean Peninsula, the flawed nature of the nuclear umbrella shows the clear limit, and even the Nuclear Consultative Group (NCG) cannot handle the security anxiety of South Koreans. Extended deterrence is not reassuring enough to permanently prevent South Korea from going nuclear, and there are considerably few talks about the ironic duality of the non-proliferation regime. Washington’s proxy nuclear defence commitment loses credibility if it thinks nuclear retaliation is risky.
Eventually, Seoul now admits the paradox to which it has turned a blind eye: allies’ hands are tied by security shackles even amid existential threats of dictators who acquiesce to one another’s advanced nuclear weapons, unlike the US movement to curb allied proliferation. This is why an increasing number of Koreans now believe that Seoul could offset the current nuclear standoff by acquiring what it wants against worsening regional security, facing multiple nuclear-armed authoritarian regimes.
Nuclear South Korea would be a more capable ally with other supplementary forces, such as missile defence and a stronger Navy with nuclear-powered attack submarines and ballistic missiles, in coordination with the South Korea-US alliance. South Korea standing alone with its indigenous nukes shouldn’t mean the decoupling of the alliance in any case. It would rather be the opposite.
Different schools of nuclear discourse in South Korea
Since the mid-2010s, considering such widespread public sentiment, both proliferation and non-proliferation schools in Korea have been actively discussing whether South Korea should go nuclear for its future national security.
Before the emergence of Trumpism, it can be said that the anti-nuclear arguments made by the non-proliferation school held overall dominance in the nuclear discourse. Several experts are sceptical of South Korea’s nuclear armament for similar reasons and possibilities: severe economic sanctions that could paralyse the South Korean economy, fall to a pariah state like North Korea, mark the end of the ROK-US alliance, lead to the fall of the non-proliferation regime, and trigger of worsening worldwide security.
Ancilliary, the Korean Navy prefers more advanced assets for active operations at the Blue Sea, raising a need for LEU (low-enriched uranium) for the propulsion system of its next-generation submarines.
Meanwhile, the proliferation school has risen over the last 10 years because of North Korea’s slim de-neuclarisation chances, Russia’s nuclear coercion against Europe, and China’s drastic nuclear build-up. The growing number of experts within this school argue that non-proliferationists’ sanction logic is overly exaggerated. They also see that South Korea’s nuclear weapons would let the state take a more responsible role on the global stage as a key US ally and that such a change of national status would upgrade the ROK-US alliance, as well. Also, the school realistically perceives that the Nuclear Proliferation Treaty is cracked due to officially acknowledged and de facto nuclear weapon states’ lukewarm posture toward the treaty’s goal of reducing nukes, the hostility of nuclear-ambitious states like Iran and North Korea, and the provision of nuclear-powered attack submarines to Australia under the AUKUS framework (a trilateral security partnership between Australia, the United Kingdom, and the United States). In terms of security, thus judging that South Korea is already more than justified to go nuclear for self-defence, the proliferation school expects that strategic independence and flexibility vis-à-vis North Korea and China would be given to Seoul after nuclearisation.
After years of the two schools’ heated debates, a new school of thought has emerged suggesting a more prudent approach to meet in the middle: nuclear latency. Nuclear latency refers to acquiring essential capabilities as a nuclear threshold state. South Korea is expected to be no longer able to store nuclear waste generated from its nuclear power plants; thus, the country will need to reprocess and recycle it through a nuclear waste reprocessing facility. Ancilliary, the Korean Navy prefers more advanced assets for active operations at the Blue Sea, raising a need for LEU (low-enriched uranium) for the propulsion system of its next-generation submarines. So to speak, nuclear latency is the most reasonable option that could fulfil industrial and security needs, sustaining South Korea’s nuclear energy research and development. Compared to the other two schools of thought, the latency option is expected to incur the least costs about which anti-nuclear experts are concerned, as it does not include the possession or production of weapon-grade nuclear warheads.
As the international system could not curb the nuclear advancement of authoritarian states, the nuclear discourse in South Korea has grown more than a storm in a teacup.
Conclusion
Hostile neighbours in the region possess and continue to enhance their nukes, while US allies remain without. As the international system could not curb the nuclear advancement of authoritarian states, the nuclear discourse in South Korea has grown more than a storm in a teacup. US allies now have complaints about Washington’s strategic inflexibility that only limits allies from taking self-defensive measures.
South Korea is aware of how the US moved frantically during the Cuban Missile Crisis. South Koreans think the same crisis is looming over Northeast Asia. Any other states geographically positioned in the peninsula would have nuclearised earlier.
South Korea is under direct threat of nuclear-armed neighbours. The majority of Koreans think nuclear armament is not the best option or a panacea, but there is a consensus that nuclearisation is inevitable. Seoul endured the status quo and remained non-nuclear for decades, even after neighbours possessed nukes. However, the worsening regional nuclear security now strains such long patience. South Korea is reaching the end of its tether.
Daehan Lee is a researcher of the ROK Forum for Nuclear Strategy (ROKFNS).
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