Seventy-five years ago, an unexpected event on the Korean peninsula changed the world. In the coming years, that history may repeat itself: an increasingly likely development there has the potential to transform the entire international order once again.
In June 1950, forces from communist North Korea invaded the non-communist south. The United States dispatched troops to prevent South Korea from being defeated and occupied, and three bloody years of fighting followed. The Korean conflict spread the Cold War, previously confined to Europe, to Asia and beyond. It also turned that conflict from a largely political and economic contest into a military one as well. Those were major alterations in international politics, and they established patterns that persisted for four decades. Now, seventy-five years later, if the government of South Korea decides to acquire its own nuclear weapons, that, too, could transform international politics, and not only in East Asia but the world over.
The Korean War left the peninsula divided between the communist North and the capitalist and ultimately democratic South. Since then, South Korea has far outstripped its northern rival in economic terms, but North Korea has had one success: it has acquired its own stockpile of nuclear weapons, to which the South Korean government may soon feel the need to respond by building nuclear weapons of its own.
A 1994 agreement between the United States and North Korea was intended to prevent the North Koreans from building these weapons but they secretly violated it and conducted their first nuclear test in 2006. They have steadily increased both the numbers and the range of their nuclear weapons in the two decades since. During that time, South Korea has relied on the United States, with its large nuclear arsenal, to prevent an attack by the North. In the same way, the European members of NATO rely on America to protect them from nuclear-armed Russia and America’s non-Korean Asian allies – Japan especially – depend on the nuclear weapons of the United States to check nuclear-armed China.
The nuclear protection the United States has provided to its allies for decades has come to be known as “extended deterrence.” The term means that with its nuclear armaments the United States prevents attacks not only on the fifty American states but also against countries, most of them far from the American homeland, that Washington has promised to protect. These countries have for decades sheltered safely under the American “nuclear umbrella.” American deterrence thus extends beyond North America to cover allied countries on the far sides of the Atlantic and Pacific Oceans.
Effective deterrence requires that the country being deterred believes that the country doing the deterring will respond forcefully to an attack. To be effective, that is, deterrence must be credible. To remain deterred, North Korea, Russia, and China must believe that if they attack an American ally, the United States will launch a punishing military reprisal against them. Now, however, the South Koreans are becoming increasingly skeptical that the American nuclear guarantee commands sufficient credibility to safeguard them against the totalitarian, aggressive, unpredictable, nuclear-armed North Korea. Two developments have called the American commitment on the Korean peninsula into question.
First, North Korea is close to having, if it does not already have, the capacity to hurl nuclear-tipped missiles across the Pacific Ocean and strike the United States itself. The American promise to attack North Korea in response to a North Korean attack on the South was easy to believe – that is, it was credible — when the United States itself was immune to a major military response from the North Koreans. The end of that immunity weakens the promise on which effective deterrence depends. To be sure, the United States faced this problem in Europe during the Cold War when the Soviet Union achieved the capacity for a nuclear strike on North America. Extended deterrence did protect Western Europe throughout that conflict, but one of the reasons it did so seems of increasingly doubtful relevance to South Korea now: this is the second development pushing that country toward becoming a nuclear-weapon state.
It is that relations between the United States and South Korea are becoming acrimonious and increasingly unpredictable. The root of the problem is the economic relationship between the two countries, and in particular the tariffs the present administration has imposed on South Korea (as well as on many other countries). The economic friction inevitably affects – and infects – security ties, and in particular South Korean faith in the reliability of the United States as its nuclear protector.
No doubt as a consequence of these developments, polls show South Koreans are increasingly favorably disposed to depending for their protection against their communist neighbor not on the United States but rather on nuclear armaments of their own. Those would be inherently more credible to North Korea as a deterrent than the nuclear forces of another country, and South Korea has the technological capacity to build them in short order.
South Korean nuclear weapons would transform the security arrangements of the Korean peninsula but would be all too likely to have major effects far beyond it as well. The nuclearization of democratic Korea has the potential to trigger a “nuclear cascade,” in which countries around the world that have eschewed such weapons because they have believed that those of the United States protect them change their minds.
A cascade would resemble a run on a bank. Just as depositors rush to withdraw their money if they fear that a bank is heading for insolvency, a fear that comes from seeing other depositors make withdrawals, so if one important ally of the United States decides that the American nuclear guarantee has ceased to be credible, other allies may reach the same conclusion and act accordingly. Nuclear proliferation among these allies, once begun on the Korean peninsula, could spread to the rest of East Asia, to Europe, and to the Middle East as well.
The United States has historically opposed proliferation on the grounds that the greater the number of independently-controlled nuclear arsenals that come into being, the greater will be the chances that a nuclear war, with all of its attendant horrors, will take place. Moreover, the conditions that kept the two nuclear superpowers of the Cold War era, the United States and the Soviet Union, from fighting each other directly would not be present elsewhere. The size of the superpowers’ nuclear arsenals gave each of them the capacity to launch a devastating retaliation in response to an all-out attack by the other, which provided both of them with credible deterrence.
A nuclear cascade would turn countries without the resources to assemble large forces into nuclear-weapon states. In addition, some of them would be located far closer to their nuclear-armed adversaries than the United States and the Soviet Union were to each other. The modest size of their nuclear arsenals and their proximity to their adversaries would force such countries to put their nuclear weapons on a hair trigger, to be launched at the first sign of an incoming attack. They would likely feel obliged, that is, to adopt a nuclear policy of “use it or lose it.” That would, at the very least, make their home regions dangerously unstable.
A proliferation cascade could also lead to actual wars, in the form of preemptive attacks for the purpose of terminating the nuclear-weapons programs of countries seeking their own nuclear weapons before they could produce such weapons. Such preemptive attacks would come from their nuclear-armed would-be conquerors. North Korea might attack the South; China might attack Taiwan; Russia might step up its attacks on Ukraine, perhaps even bringing nuclear weapons into play.
While Israel launched a preemptive attack on the Iranian nuclear weapons program in June, it did so for defensive reasons, to thwart the aggressive designs of the Islamic Republic; and it carried out its mission without resorting to nuclear weapons. By contrast, preemptive attacks by North Korea, China, and Russia would have an aggressive rather than a defensive purpose and might not remain non-nuclear. The Israeli strikes made the world, temporarily at least, a more stable and peaceful place. North Korean, Chinese, and Russian attacks would have the opposite effects.
A decision to acquire nuclear weapons by a democratically-elected South Korean government, made for purely defensive purposes as the best and perhaps only way to preserve its independence and its democratic political system, would be entirely legitimate. It is all too plausible, however, to imagine a worst case in which such a decision would set in motion a series of events that would make the world a more dangerous and violent place than it has been in at least eight decades.
