South Korea and nuclear weapons

The nuclear weapons debate in South Korea has reignited. On June 21, the Institute for National Security Strategy advised the South Korean government to consider development of an independent nuclear force. The following week, putative conservative party leaders Han Dong-hoon and Na Kyung-won each advocated the same. Prime Minister Han Duck-soo clarified that South Korea is not considering nuclear armament, but qualified his remarks with a suggestive “for now.” Two-thirds of the South Korean public (still) favors an indigenous nuclear deterrent.

The 2023 Washington Declaration, and specifically the U.S.-South Korea Nuclear Consultative Group, was supposed to stop this sort of rhetoric by reinforcing U.S. extended nuclear deterrence. So, what happened, and how should we think of South Korea’s interest in acquiring nuclear weapons?

The reasons for South Korea’s return to worry are not capricious. First, North Korea has continued to build out its nuclear arsenal — denuclearization is now an impossibility. Seoul will face a hostile, nuclear-armed Pyongyang for the foreseeable future. Second, the robustness of the new Russia-North Korea military alliance is unclear, but Moscow’s support has made Pyongyang more dangerous.

Third, fever-pitch turmoil in U.S. politics is making Washington seem like a wobbly ally. President Joe Biden’s disastrous recent debate performance, and follow-on Democratic Party meltdown including calls for Biden to forgo a second term, have seemingly confirmed the incumbent president’s diminished capacities. This has further tilted the U.S. presidential election toward a Donald Trump victory, with aggregated polls setting his chances of winning at 72 percent.

A Trump 2.0 presidency would likely be as erratic, unconventional and transactional as the first. For South Korea, this could mean anything from alliance abandonment by the U.S. to acquiescence to Seoul’s acquiring nuclear weapons. Trump has himself broached the latter possibility, as have numerous Trump-adjacent advisers under consideration for high-ranking security and defense appointments in a new Trump administration.

Taken together, these developments — not to mention Chinese revisionism — seemingly make a good case for South Korea to explore the possibility of a nuclear weapons program. In practice, however, South Korea going nuclear is a massively difficult and fraught undertaking.

The obvious problem is that current U.S. policy is against it, and Washington has leverage — economic, military/security, defense-industrial, diplomatic — to make Seoul’s nuclear weapons acquisition too painful. Additionally, there are technological challenges, notably with fissile material production, warhead design and the formation of a nuclear weapons “ecosystem,” including the relevant human capital. The international community is also against South Korean nuclear weapons.

But let us assume all those problems are solved. If Seoul wants nuclear weapons, it still has many difficult questions to answer.

What are you willing to pay for them? A nuclear weapons program is expensive, costing billions of dollars annually. A South Korean race to nuclear breakout would also require a huge upfront outlay. This should not be financed with military budget cuts in other areas, as nuclear weapons are not a panacea. Seoul’s nuclear weapon expenditures would be in addition to maintaining its conventional military forces, which are needed for conventional deterrence and warfighting.

Where are you going to test nuclear warheads? South Korean governments would face huge political opposition from localities near any potential nuclear test site.

What scale arsenal do you want? A handful of nuclear weapons for a countervalue second strike capability is insufficient, given North Korea’s growing, diversified arsenal. Rather, South Korea would likely need 100+ warheads, including tactical nuclear warheads for counterforce targets. This requires a full-fledged program.

How are you going to ensure nuclear command-and-control and field intelligence/surveillance/reconnaissance assets for accurate targeting? Being a responsible nuclear state requires establishing systems in which nuclear weapons are always used precisely for an intended target when the appropriate command authority gives a launch order, and are never used otherwise. This is a complex technical and human psychology task.

How will you deliver nuclear weapons, and where will you store them? Should South Korea have ground-launched missiles? Air-launched missiles and/or bombs? Submarine-launched missiles? Two of the three? A full nuclear triad? There are trade-offs — cost, promptness, security/reliability, flexibility etc. — to these platforms. As for storage, it will be politically costly to convince South Korean citizens to accept nearby warhead storage.

Are you prepared to develop a nuclear strategy, doctrine and posture? Nuclear weapons are a powerful tool, but learning the concepts to use the tool is hard. Misguided nuclear strategy means nuclear weapons will not support your security objectives. Misguided nuclear doctrine and posture mean your nuclear weapons can be destabilizing, leaving you less secure.

Are you willing to accept a period — 2-5 years — of profound uncertainty and risk as South Korea goes through the nuclear weapons development process? South Korea’s neighbors would likely attempt to thwart its nuclear ambitions, perhaps through attack.

Are you willing to accept a regional domino effect? If Seoul acquires nuclear weapons, Japan may be next. Perhaps Taiwan. North Korea would likely accelerate development of its arsenal.

South Korea’s desire for nuclear weapons is understandable, but extremely tricky.

Mason Richey is professor of international politics at Hankuk University of Foreign Studies, president of the Korea International Studies Association, and editor-in-chief of the Journal of East Asian Affairs.