North Korea’s growing nuclear might threatens the security status quo in the Korean Peninsula. Since the ratification of the 1953 Mutual Defense Treaty, the United States has committed to the South’s defense. That was a relatively easy promise to make in the early years since America’s liability was limited to the battlefield. Although the Korean War was ferocious and destructive, as in previous global conflicts, the violence barely touched the American homeland. And until recently, North Korea had no way to reach the United States or even its Pacific possessions. Washington could easily adjust its policy for its advantage—for instance, like it did in 1953 by choosing not to battle on to unify the peninsula despite then-South Korean President Syngman Rhee’s refusal to sign the armistice.
However, policymakers in Seoul appear to be increasingly nervous about the viability of extended deterrence, both conventional and nuclear. Last year, the North’s flurry of missile testing, more than 90 ballistic missile tests, dominated public attention. Pyongyang has been striving mightily to match nuclear warheads to intercontinental ballistic missiles, thereby putting American cities at risk. Would Washington stand by its commitment if Kim could deliver “fire and fury” to the continental United States?
Ukraine is not a treaty ally of the United States but still has intensified these fears. The Biden administration’s evident concern about provoking Russian escalation—especially Moscow’s potential use of nuclear weapons, though mostly slowing rather than halting increasingly sophisticated arms transfers—raises questions about the United States’ reaction if the North gained a similar (though much smaller) nuclear capability.
Yoon explained: “What we call extended deterrence was also the U.S. telling us not to worry because it will take care of everything. But now, it’s difficult to convince our people with just that.” Yoon indicated that Seoul would be given a hand in the use of American nukes: “The nuclear weapons belong to the United States, but planning, information-sharing, exercises, and training should be jointly conducted by South Korea and the United States.”
It’s a reasonable concern. Of course, American officials responded by expressing their deep and everlasting commitment to South Korea. The White House cited the alliance’s “rock solid foundation” in May 2022. The administration further marked the president’s visit to South Korea, stating: “President [Joe] Biden affirms the U.S. extended deterrence commitment to the ROK using the full range of U.S. defense capabilities, including nuclear, conventional, and missile defense capabilities.”
However, generic guarantees remain of little value. Ukrainians remember the toothless 1994 Budapest Memorandum, offered in exchange for Kyiv’s agreement to yield its Soviet-era nukes, which offered no serious remedy and could not have been enforced even if it had.
Imagine a future conflict in which U.S. and South Korean forces are poised to march northward, and the North issues an ultimatum, threatening nuclear attacks on America’s homeland if the allies do not withdraw from North Korean territory—or perhaps if Washington doesn’t withdraw from the conflict entirely. From the likely perspective of Washington, nothing in South Korea is worth sacrificing a dozen U.S. cities and millions of Americans for. What would a future president do?
That’s why there’s such powerful South Korean backing for an independent deterrent. There is strong public support, though most people probably have not considered the inevitable complications. Some officials, including retired Gen. Leem Ho-young and National Assembly politician Cho Kyoung-tae, are currently pushing the idea. And, as noted earlier, Yoon just brandished the possibility. However, official Seoul policy generally prefers Washington to provide the weapons, though their placement on the peninsula wouldn’t guarantee the willingness of any particular administration to use them.
Washington overwhelmingly opposes a South Korean bomb. One reason is its commitment to nonproliferation in principle. Also, though usually left unstated, is its desire to preserve America’s Asian predominance by maintaining its nuclear monopoly among friends.
Yet this policy conundrum may be changing some minds. For instance, the Hoover Institution’s Michael Auslin raised the issue early: “While few believe Kim Jong Un would launch an unprovoked nuclear strike, most seasoned Korea watchers believe that he would no doubt use his arsenal once it became clear he was about to lose any war that broke out. As this risk increases, Washington will find it increasingly difficult to avoid reassessing the country’s multi-decade alliance with South Korea. The threat to American civilians will be magnified to grotesque proportions, simply because Washington continues to promise to help South Korea.”
Steve Chabot, a long-serving Ohio congressman, recently made the startling suggestion that Washington “enter into talks with both Japan and South Korea about considering nuclear weapons programs themselves.” He allowed that he hoped it would not be necessary to proceed down this path, but that “even talking with [the South Koreans] would get [China’s] attention, and maybe they would actively act to restrain North Korea for the first time.”
In the past, some experts, including myself, offered this possibility as a reason to at least begin such discussions. However, in light of Pyongyang’s growing arsenal, the moment to prevent a North Korean nuke almost certainly has passed. Even if Beijing was willing, it would be a bit like trying to refill Pandora’s box. In any case, China is no less concerned about preserving stability on its border than before and far less interested in doing the United States a favor after Washington moved toward economic as well as military containment.
In which case, Chabot’s talks would lead to the obvious question: Would the United States tolerate its allies creating nuclear weapons? A South Korean bomb would inevitably spark debate in Japan, especially with the Kishida government committed to a major increase in military outlays—simultaneously with a shrinking population, expected to drop by almost 20 million people (or around 17 percent) by 2050, making it harder to field sizable armed forces.
Dropping extended deterrence would end Kim’s ability to hold the American homeland hostage. There would be potential advantages beyond North Korea. Beijing would face a different risk calculus in pressing its territorial claims militarily. One could even imagine the transfer of nuclear technology to Taiwan; although to prevent any Chinese attempt to preempt the United States, the United States might have to provide weapons directly.
However, the downsides of such a policy are also obvious. More nukes would create additional opportunities for accidents, leaks, and threats, and they could exacerbate any wars that occurred. China might respond by speeding up its nuclear program. North Korea would be less inclined to negotiate any limits on its arsenal, though it might not be willing to do so anyway. Other nations would naturally ask: If the United States is unwilling to confront a nuclear North Korea, would it risk war with a nuclear Iran or even Russia? Other American allies might consider their nuclear options.
But the possibility of allowing if not encouraging friendly proliferation no longer can be dismissed, especially since South Korea could decide to proceed without Washington’s approval. If the United States was unwilling to sanction Israel, gave up punishing India and Pakistan, and failed to halt North Korea, could it stop Seoul and perhaps Tokyo as well? Would the price of doing so be worth the cost? Would doing so be even possible? The United States would be unlikely to end alliances and/or impose sanctions, especially while attempting to contain China.
For years, allowing allied states to go nuclear was inconceivable—hence concerted U.S. pressure against both South Korea’s and Taiwan’s nuclear programs. However, that was before North Korea was set to become a substantial nuclear power. Extended deterrence in Asia then posed less risk to the American people. Unless U.S. policymakers are prepared to risk everything for South Korea, they must contemplate the previously unthinkable: a South Korean bomb.
