Over the past few months, many Western analysts have been deeply concerned about the possibility that Russian President Vladimir Putin might deploy a tactical nuclear weapon in Ukraine. But Putin is not the only autocrat who could resort to weapons of mass destruction. Look no further than North Korea. In the past year, the country’s leader, Kim Jong Un, has tested a submarine-launched ballistic missile, a train-mounted ballistic missile, a new surface-to-air defense missile system, a long-range strategic cruise missile, and multiple hypersonic missiles. And there are indications that North Korea is preparing its seventh nuclear test, possibly to showcase a more compact, next-generation tactical nuclear weapon.

The fact that North Korea has had nuclear weapons for so long (its first nuclear test was in 2006) has inured analysts and policymakers to the gravity of the threat. The North can now credibly threaten the continental United States with nuclear weapons. But the threat goes beyond U.S. domestic security: North Korea’s development of weapons of mass destruction (WMD) could spark an arms race in northeast Asia. Kim’s saber rattling has increased public support in South Korea for that country to acquire its own nuclear capability, something that previously would have been regarded as implausible. A South Korean decision to go nuclear would prod China and Japan to augment their own weapon arsenals. With no easy solutions, the Biden administration has failed to articulate a policy response to these developments. It needs to get more engaged to prevent another crisis from spinning out of control.

Missile Man

Kim has been flexing his military muscle in provocative ways. In 2017, North Korea crossed the twin thresholds of developing a thermonuclear weapon and flight-testing an intercontinental ballistic missile, and it is now focused on developing tactical nuclear weapons intended for use against targets on or near the peninsula, which could include ports, airfields, command-and-control facilities, and missile defense installations belonging to both South Korean and U.S. forces. In April 2022, the North tested eight nuclear-capable missiles with different ranges from five different launch sites to demonstrate its capability to hit a variety of targets in South Korea. Similar tests followed in September and October to simulate showering South Korea with tactical nuclear weapons.

Even as Kim has been expanding his WMD arsenal, he has also been threatening to launch a preemptive attack. These threats are not new, but the fact that Kim is publicly reserving the right to mount a first strike is nevertheless concerning. On September 9, at a meeting of North Korea’s rubber-stamp parliament, Kim announced five conditions under which North Korea would launch a preemptive nuclear strike, effectively unveiling a new “first use” doctrine. The conditions are not only when a nuclear attack against North Korea is imminent but also when a nonnuclear strike on the country’s leadership or “national nuclear force command body” has been carried out; when a military attack on important state targets has occurred; or when the regime deems that only nuclear weapons can prevent the expansion of a conventional war. Kim also introduced legislation to enshrine North Korea’s nuclear status and asserted that he will never again engage in talks about denuclearization.

Kim is intent on sundering the U.S.–South Korea alliance.

Kim is clearly signaling that if a conventional strike is launched preemptively or is imminent against North Korea’s leadership or nuclear forces, he reserves the right to respond with nuclear weapons. In doing so, he is addressing a plausible scenario: as recently as 2017, U.S. policymakers discussed the possibility of a “bloody nose”—or preemptive—strike against North Korea. By threatening first use, Kim is also positioning North Korea to be able to employ nuclear blackmail against South Korea to coerce it into political concessions, perhaps ultimately with the aim of getting some kind of unification arrangement on North Korean terms.

Whatever he does, Kim is intent on sundering the U.S.–South Korea alliance by making it too costly and risky for Washington to come to Seoul’s aid in a crisis. He may well calculate that the United States will not respond to a North Korean attack on South Korea because it will be too concerned about a North Korean nuclear attack on U.S. bases in Asia or even against the United States itself. Kim could be encouraged by Putin’s nuclear saber rattling to imagine that the United States can be forced to back off with such threats. To be sure, the United States hasn’t stopped arming Ukraine and has even increased its supply of weapons, but the Biden administration has drawn sharp limits on this support; for example, the U.S. military has not provided longer-range weapons and has not sent any U.S. troops to Ukraine, even as trainers.

An Ominous Global Climate

This North Korean buildup is occurring in an international climate that is favorable for North Korea. Washington’s mounting animosity with both China and Russia means that those countries are less likely than ever to cooperate with the United States and its allies in strengthening sanctions on North Korea. Consider what happened when North Korea sent an intermediate-range missile flying over Japan on October 4, 2022. The missile flew 4,500 kilometers—farther than any other missile previously launched by North Korea—before landing in the Pacific Ocean, and UN Secretary-General António Guterres decried the bellicose move as a “reckless act.” But China and Russia blocked the UN Security Council from condemning the attack. The U.S. representative to the United Nations, Linda Thomas-Greenfield, decried how “two permanent members of the Security Council have enabled Kim Jong Un.” In addition to Russian and Chinese intransigence to holding North Korea accountable at the UN, those two countries are the focus of U.S. policymakers, which leaves the Biden administration with less bandwidth to focus on the North Korea threat.

Russia’s invasion of Ukraine, moreover, has underlined for the North the importance of having nuclear weapons. Kim no doubt questions whether Putin would have launched his invasion if Ukraine had not given up its nuclear weapons in 1994. The war reinforces the lessons Kim has drawn from Iraq and Libya, where strongmen who gave up WMD programs were overthrown and killed. Only WMDs, it seems, can guarantee regime survival.

All these developments have understandably unsettled South Korea—a nuclear-free state that is now facing a nuclear-armed neighbor. South Korea has traditionally relied on the American nuclear deterrent to stay safe, but U.S. President Donald Trump flirted with removing U.S. troops from South Korea if Seoul did not dramatically increase the amount of money it paid to support them. South Korea, and other U.S. allies, have good cause for concern about what would happen if Trump or another “America first” candidate were to win the presidency in 2024 or beyond. It is unclear whether they could still rely on the U.S. nuclear umbrella, especially with the United States’ growing vulnerability to a North Korean nuclear attack.

South Koreans are increasingly debating how their country can strengthen its deterrence. They may press Washington for the rotation of more nuclear-capable U.S. weapons systems, such as B-52s or F-35s, to their country. They could ask for the introduction of NATO-style sharing of nuclear weapons between the United States and South Korea or for the redeployment of U.S. tactical nuclear systems, which were pulled out of South Korea in 1991. And then there is the most radical option of all: namely, South Korea itself could go nuclear. In a recent poll, 55 percent of the population supported such a move. That is an increase of ten points in one year, indicating South Koreans’ accelerating alarm about North Korea’s WMD buildup.

Eyes on Washington

The U.S. government is unlikely to support any of these possible South Korean policy responses aside from occasional rotations of nuclear-capable U.S. aircraft and ships to South Korea. Washington is particularly opposed to the redeployment of U.S. tactical nuclear weapons to South Korea or the South Korean government developing its own nuclear weapons. Many in the U.S. military simply do not see the need for such steps since the United States can hit any target in North Korea using highly precise conventional weapons. If the conflict escalates and a nuclear strike is necessary, the weapons can be launched from secure U.S. platforms such as ballistic-missile submarines or long-range bombers that do not need to be based on the peninsula.

American military experts fear that if U.S. nuclear weapons were stationed in South Korea, they could make tempting targets for a preemptive North Korean attack. From the U.S. perspective, South Korea should trust that having 28,500 American troops in South Korea is evidence of the deep U.S. commitment to its defense. But these arguments do not convince many skeptics in South Korea, who fear that North Korea’s nuclear arsenal could deter U.S. intervention and that the election of an isolationist president in the United States could put the alliance at risk.

South Korea President Yoon Suk-yeol is unlikely to take the most radical step—starting a nuclear weapons program—because South Koreans remain divided on the issue (the liberal opposition party, which is in the legislative majority, is firmly opposed), and it would come with many pitfalls. For one thing, it would risk creating a rift with the United States—as previously happened in the 1970s when then President Park Chung-hee launched a clandestine nuclear program but abandoned it in exchange for security guarantees from the United States. To pursue nuclear weapons legally, South Korea would need to withdraw from the Nuclear Nonproliferation Treaty or risk international sanctions. In the aftermath of such a decision, South Korea could be isolated internationally—as Pakistan was initially after it went nuclear—and the U.S.–South Korea alliance could come under fresh strains. (It is true, however, that Israel and India are hardly international pariahs despite their nuclear weapons programs.) Such a step would, moreover, raise the risk of a preemptive North Korean attack before South Korea could make its weapons program operational. And, of course, Japan and China could respond by augmenting their own weapons programs. Japan could go nuclear; China could expand its already substantial nuclear arsenal.

South Koreans remain divided on starting a nuclear weapons program.

A less provocative option could be for the United States to introduce “nuclear sharing,” a practice it engages in with NATO allies. The United States has long had such arrangements with several NATO states, which involve stationing U.S. nuclear weapons on their territories to be delivered by aircraft and pilots from those countries in the event of a conflict. If a major war were to break out, NATO’s Nuclear Planning Group has to give its explicit approval to deploy these weapons; the U.S. president and British prime minister would have to provide authorization as well. Only then would B-61 bombs be delivered by European aircraft.

One could imagine a similar arrangement being developed with South Korea, one of the United States’ most important non-NATO allies. The Pentagon may well be correct that, from a strictly military standpoint, such a policy may not have much to recommend it. It could, however, help to bolster deterrence and reassure the South Korean public in the face of North Korea’s looming threat.

It is obvious why none of the options to bolster South Korean deterrence have yet been implemented: all come with major drawbacks. But there is a strong sense in South Korea that something needs to be done to address its heightened security concerns. The threat from North Korea is growing, and since Trump’s presidency, U.S. security guarantees appear less sturdy. The Biden administration needs to act to bolster the alliance as it comes under increasing strain.

A task force convened by the Chicago Council on Foreign Relations offered some useful recommendations, including bringing South Korea, along with Japan and Australia, into an Asian Nuclear Planning Group, which would foster greater understanding of U.S. nuclear policies. South Korea could also be included in the Quadrilateral Security Dialogue, the alliance that unites the United States with Australia, India, and Japan. The problem, of course, is that whatever Biden does today, a future president could undo. Still, these moves could provide a measure of reassurance to South Koreans that they will not be abandoned.

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  • SUE MI TERRY is Director of the Asia Program and the Hyundai Motor–Korea Foundation Center for Korean History and Public Policy at the Wilson Center. A former CIA analyst, she served on the National Intelligence Council from 2009 to 2010 and the National Security Council from 2008 to 2009.
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