Why South Korea is debating a nuclear weapons program

Political momentum is growing in South Korea for acquiring nuclear weapons – a fringe idea only a few years ago – amid frustration over North Korea’s aggressive ramping up of its nuclear arms and missile capabilities.

South Korean President Yoon Suk-yeol warned earlier this month that his country might go nuclear if security keeps deteriorating on the Korean Peninsula. Although he later walked back the comments, Mr. Yoon’s willingness to raise the nuclear option publicly reflects its popularity among South Koreans, 71% of whom favor their country developing its own nuclear arsenal, according to a poll last year.

“The South Koreans are very concerned about deterring a whole range of North Korean activities,” says Ankit Panda, Stanton senior fellow in the Nuclear Policy Program at the Carnegie Endowment for International Peace. “The perception is that the only way to deter … is having nuclear weapons of your own.” 

The debate over nuclear weapons reveals a deepening sense of insecurity in South Korea stemming not only from North Korean provocations but also from China’s increasing nuclear arsenal and Russia’s nuclear saber rattling. And, experts say, it has serious implications not only for South Korea and security in Northeast Asia, but also for the global nonproliferation regime.

“It’s a rare and remarkable moment any time a U.S. ally moots acquisition of nuclear weapons,” says Mr. Panda. “It sets off alarm bells in Washington.”

Nevertheless, both Seoul and Washington have reiterated that they are working together to solidify their alliance and strengthen their deterrence against North Korea – a priority of both the Yoon and Biden administrations. 

On Tuesday in Seoul, U.S. Defense Secretary Lloyd Austin and South Korean Defense Minister Lee Jong-sup held talks and pledged to bolster planning and expand joint exercises to deter North Korea. In February, the two sides will hold a tabletop exercise to facilitate “response options to deal with the DPRK [North Korean] nuclear threat,” they said in a joint statement.

“Right now we have the United States that provides us with a nuclear deterrent,” says retired Lt. Gen. In-Bum Chun, former commander of the Republic of Korea Special Warfare Command. “But we are more concerned than we used to be,” he says. “Korean people are looking for answers.” 

New security environment

North Korean leader Kim Jong Un this month directed his country to mass-produce nuclear weapons, while heralding a new law that allows Pyongyang to launch preemptive nuclear strikes. He also called for North Korea to develop a more powerful intercontinental ballistic missile, following the testing of more than 90 ballistic and cruise missiles last year. And experts say North Korea may be preparing for a seventh nuclear test – the first since 2017.

“Given all of the advancements that North Korea has made in their nuclear weapons program, and changes in the geopolitical environment, there’s been a lot more anxiety in South Korea about how they deal with a nuclear North Korea – and what the U.S. would actually do,” says Jenny Town, a senior fellow at the Stimson Center and director of Stimson’s 38 North Program.

South Korea’s concern has grown along with Pyongyang’s ability to put the continental U.S. at risk. Despite the presence of 28,500 U.S. troops in their country, South Koreans have doubts about whether they can rely on what is known as the U.S. nuclear umbrella, or “extended deterrence,” whereby the U.S. is bound by a treaty to swiftly retaliate for any attack on South Korea.

“Even when the U.S.-ROK [Republic of Korea] alliance is strong, when North Korea intensifies its provocations,” questions arise about the “United States’ credibility of extending nuclear and conventional deterrence,” says Ji-Young Lee, associate professor of international relations at American University’s School of International Studies. “This is … a reflection of North Korea creating another layer of crisis.”

Moreover, South Koreans are drawing a troubling lesson from Russia’s invasion of Ukraine, and Moscow’s use of nuclear threats to deter the U.S. and other countries from intervening directly. 

South Korea is “watching how the U.S. has reacted to Russia’s invasion of Ukraine,” says Ms. Town. “That really raises anxieties … like what happens if North Korea were to attack? Would the U.S. show a similar restraint?”

South Koreans warm to nuclear armament

South Korea’s weighing of the nuclear route gained the spotlight with the 2022 election of Mr. Yoon, a populist and conservative leader whose hard-line approach toward Pyongyang contrasts sharply with his predecessor Moon Jae-in’s focus on reconciliation.

Mr. Yoon has aligned South Korea’s overall foreign policy more closely with that of the U.S. and its Indo-Pacific strategy. He has emphasized strengthening deterrence through the trilateral partnership between the U.S., South Korea, and Japan, which in November condemned Pyongyang’s multiple missile launches and promised a joint response if North Korea conducts a seventh nuclear test.

In this context, Mr. Yoon’s statements on the nuclear option are intended as more of a warning to Pyongyang, says Dr. Lee. But Mr. Yoon and other South Korean officials are reportedly interested in the U.S. deploying tactical nuclear weapons to South Korea, three decades after Washington removed them in 1991. Washington has stated it does not support the idea.

Many South Koreans do, says Lieutenant General Chun. They think that “maybe a balance will be created on the Korean Peninsula, and North and South will both understand unification by force is out the window,” he explains.

A report on North Korea released this month by a U.S. think tank recommends Washington and Seoul should engage in preliminary planning for such a possible option. 

“The allies should consider tabletop planning exercises for the possible redeployment of U.S. nuclear weapons to South Korea,” said the report by the Center for Strategic and International Studies. It stressed such planning should be “pre-decisional.” “The timeline and scope of weapons, such as low-yield nuclear SLCMs [submarine-launched cruise missiles] or gravity bombs, should be left deliberately ambiguous,” it said.

Need for trust

Even if discussions were to take place on the possible redeployment of U.S. nuclear weapons to South Korea, experts say South Korea is unlikely in the foreseeable future to develop its own nuclear weapons given the damage that would cause to the U.S.-South Korean alliance, the global nonproliferation regime, and South Korea’s economic interests, including its civilian nuclear industry. Such a move would make a crisis with the North more dangerous.

“If Seoul had nukes, the threats of North Korea would stay the same or get worse,” says Mr. Panda. 

A better alternative, they say, is for the U.S. to improve its extended deterrence capabilities – something U.S. officials say is underway.

“Strong, reliable U.S.-extended deterrence would be a more effective deterrent than South Korea pursuing its own nuclear program,” says Rachel Minyoung Lee, a senior analyst with the Open Nuclear Network, an Austria-based organization with the mission of reducing the risk of nuclear conflict.

Equally important, Washington must take steps to build greater trust in the U.S. commitment to safeguarding South Korea. “The South Korean people are the ones who are within range of North Korea’s tactical nuclear weapons and their means of delivery,” says Ms. Lee, a former North Korea analyst for the U.S. government. “South Koreans need stronger assurances from the U.S.”