In January, South Korean President Yoon Suk-yeol commented that his country may have to consider developing its own nuclear weapons in response to the escalating nuclear and missile threat it faces from North Korea. Although the government soon clarified that South Korea is not actively pursuing this policy, the remarks were echoed by Chung Jin-suk, the leader of Yoon’s conservative People Power Party, and even more recently by Oh Se-hoon, Seoul’s mayor and a possible 2027 presidential candidate. South Korea’s nuclear debate is no longer held only on the fringes of its politics and cannot be simply wished away. In fact, with Pyongyang’s continued military provocations, it might even be coming to a head.
Prior to North Korea’s 2006 nuclear test, there was limited public debate in South Korea about developing its own arsenal. Over the past decade of polling, there has been reliable support—held among roughly two-thirds of the South Korean public—for an indigenous nuclear weapons program. Today, support hovers around 70 percent, according to various polls, meaning the country’s leaders could develop the bomb without fear of a significant domestic backlash. Even though Kyiv never had operational control over Soviet nuclear systems, Russia’s invasion of Ukraine merely three decades after the latter decided to voluntarily relinquish its nuclear weapons has reinforced the perception among many that a nuclear deterrent is the only credible protection against a determined invader.
The question South Korea is now asking itself is not whether it is capable of building nuclear weapons, but whether the benefits of doing so outweigh the costs. Not only can Seoul withstand these costs, but they would likely be far less severe than those publicly discussed by the nonproliferation community.
For more than half a century, the treaties, agreements, arrangements, and verification tools that make up the global nonproliferation regime—in particular, the Treaty on the Non-Proliferation of Nuclear Weapons (NPT)—have largely prevented new states from developing nuclear weapons. Key to eliciting compliance with this bargain are the penalties and punishments imposed if states are found violating their safeguards agreements—above all, economic sanctions. Iran and North Korea, the most notable NPT pariahs, are among the most heavily sanctioned countries in the world, and as a global economic powerhouse, South Korea would stand to lose a great deal if it were subject to similar retribution.
Yet South Korea’s current security environment is so fraught that its decision may be understandable to many. While Seoul continues to respect the January 1992 joint declaration on the denuclearization of the Korean Peninsula, Pyongyang has gone in the opposite direction, to put it lightly.
It is precisely this threat that could help Seoul maintain moral and legal high ground—and avoid the kind of backlash Pyongyang faced for its actions. As enshrined in Article X of the NPT, South Korea has the “right to withdraw” in the case that it “decides that extraordinary events, related to the subject matter of this Treaty, have jeopardized the supreme interests of its country.” In September of last year, North Korean leader Kim Jong Un declared that his country’s nuclear status is “irreversible,” and the rubber-stamp Supreme People’s Assembly passed a law that month enshrining Pyongyang’s (self-anointed) right to launch a preemptive nuclear strike. Meanwhile, North Korea continues to lay claim to the whole of the Korean Peninsula. This publicly established threat would give South Korean leaders a powerful legal case to argue that withdrawal from the NPT to develop nuclear weapons is a matter of pure survival.
Withdrawal from the NPT in and of itself may make South Korea the target of criticism. But there’s good reason to believe that the way in which it develops its nuclear program could mitigate some of the reputational costs and diplomatic fallout.
Israel, for example, is widely acknowledged to possess nuclear weapons even though it has refrained from publicly conducting a nuclear test. Nuclear tests are particularly inflammatory because they serve as a vivid reminder to other countries of the threat they face—not to mention the environmental harm these tests cause. Yet Israel’s (test-free) nuclear status has not prevented it from becoming one of Washington’s strongest allies. While the South Korean Army would ideally want to conduct at least one nuclear test to assess and collect valuable data on its technology, it could instead follow Israel’s lead and rely on its civilian nuclear energy know-how, computer modeling, and data gathered from other countries’ nuclear tests—including North Korea’s—to quietly develop its own program. This would certainly reduce the reputational hit Seoul would take.
Further, as the case of India shows, the backlash from conducting a nuclear test would not necessarily be insurmountable. The Clinton administration criticized New Delhi’s 1998 tests and imposed a series of economic sanctions on India. But for the United States, strengthening relations with India eventually became more important than upholding the nonproliferation regime. Sure enough, by 2005, U.S. President George W. Bush and Indian Prime Minister Manmohan Singh had issued a joint statement lifting a three-decade-old nuclear trade moratorium, and the countries continue to cooperate across a range of issues today.
In today’s geopolitical context, the Biden administration has shown a willingness to put its security interests above all else in its competition against China. To that end, the United States is now party to the AUKUS security pact, whereby the United States and the United Kingdom will share nuclear propulsion technology and, potentially, highly enriched uranium with Australia. Although the AUKUS partners have vehemently stated that Australia’s intent is peaceful and that the agreement doesn’t undermine the NPT, some experts believe this creates a loophole for other non-nuclear states to develop nuclear weapons outside of the nonproliferation regime.
Critics can certainly argue that the cases of Israel, India, or now AUKUS are different from South Korea’s. Yet these cases make clear that under certain circumstances, strategic considerations can trump proliferation concerns in the eyes of the United States and its partners.
South Korea has indeed become an invaluable strategic partner to many of the countries that would be responsible for imposing costs—reputational or otherwise—for Seoul going down the nuclear route. Since the turn of the century, Seoul has forged a global network of geopolitical and economic linkages that would mitigate and perhaps even prevent any long-lasting reputational, diplomatic, or even economic backlash were it to decide to develop nuclear weapons. These include arms exports, among others, to NATO members, including the United States, in the context of Russia’s invasion of Ukraine, as well as to Southeast Asia and the Middle East; nuclear power plant construction, particularly in the Middle East so far but potentially also in Europe in the future; factories and supply chain links with the United States, Europe, India, Japan, and Southeast Asia; and burgeoning security ties with NATO, Australia, Canada, India, Indonesia, Poland, and other partners—plus trilateral United States-South Korea-Japan cooperation. Because South Korea has become so important to much of the global system, its partners would be forced to conduct a difficult cost-benefit analysis between upholding the nonproliferation regime or continuing their cooperation with Seoul. Whether implicitly or explicitly, Seoul could use these links as a bargaining tool. This may be seen as transactional, and it would be. But such is the nature of contemporary international relations.
Even economic sanctions—one of the nonproliferation regime’s most powerful tools—may not be a realistic deterrent. In 2016, China imposed unofficial sanctions on South Korea after the Park Geun-hye administration agreed to the deployment of the U.S. Terminal High Altitude Area Defense missile defense system on Korean soil. The sanctions hit the South Korean economy, but they did not wreak havoc on it, even though China accounts for 25 percent of South Korean exports. Eventually, Beijing removed the sanctions, in no small part because Beijing also needs access to South Korea’s semiconductors and other high-tech products to compete in the global economy.
Likewise, any economic measures that the United States and its allies and partners could take against South Korea would have to be balanced against deep existing economic links with Seoul. Among the world’s leaders in semiconductors, artificial intelligence, electric batteries, green ships, and 5G/6G technologies, many countries would find it difficult to sever ties with South Korea to the detriment of their own economies.
Not to mention, nuclear-armed or not, the United States, Europe, and other likeminded partners would certainly much rather have South Korea in their diplomatic and political corner as they focus on competition with China and Russia. Former U.S. President Donald Trump, if reelected, or a Trump-like successor, may even welcome South Korea stepping up and taking greater responsibility for its own security instead of “free-riding” on Washington’s largesse. Quietly, many Western officials would probably not be opposed to a nuclear South Korea in a region where it has to confront the nuclear arsenals of North Korea, China, and Russia.
The above isn’t a call for South Korea to go nuclear. That decision belongs to the South Korean leadership and people, and the Yoon government has reiterated that it does not plan to go down this route. But the developments leading Seoul to consider the nuclear option are not going to reverse any time soon, and it’s not out of line to suggest that Seoul could probably develop nuclear weapons without facing major long-term repercussions. Eventually, the rest of the world—and the United States in particular—will need to grapple with the fact that its nonproliferation regime may not be strong enough to contain one of its own.
