The South also rises: How the Korean nuclear threat could gradually, then suddenly, lead to war

“Gradually, then suddenly.”

That line from Ernest Hemingway’s novel “The Sun Also Rises” reveals a lot about the way catastrophe happens. Tragedy strikes, as if out of the blue. But in retrospect, we realize that disaster was all but inevitable, the outcome of a long train of seemingly minor events building inexorably then abruptly in catastrophe.

And that’s precisely how South Korea is going to become a nuclear weapons state — gradually, then suddenly.

First, gradually.

The systemic pressures pushing Seoul in the direction of acquiring nuclear weapons have been building for quite some time. The most obvious source of these pressures has been North Korea’s nuclear program. Since the 1960s, but with growing earnestness since the 1990s, Pyongyang has sought to acquire nuclear weapons to deter what it perceives to be an implacably hostile United States.

In the service of this goal, gradually (that is, over the course of several decades) it developed the capacity to produce weapons-grade plutonium, conducted nuclear tests, manufactured nuclear warheads, tested ballistic missiles capable of delivering these warheads to targets at ever-greater ranges, withdrew from the Nuclear Non-Proliferation Treaty, entered into and then withdrew from a number of other agreements intended to limit its nuclear program and finally in 2017 detonated what it claimed was a thermonuclear device. Gradually, as the threat posed by Pyongyang’s nuclear capabilities and posture has grown, so too has Seoul’s sense of insecurity.

And in recent years this sense has been compounded by the gradual erosion of the credibility of the U.S. extended nuclear deterrent. That credibility rests on the assumption that the United States would be able to respond to a North Korean conventional or nuclear attack against the South without fear that this response would in turn trigger a retaliatory attack against the U.S. homeland.

That was the bedrock strategic reality that underpinned the 1953 Mutual Defense Treaty between Washington and Seoul, a reality that has persisted for decades after. But as North Korea has developed an increasingly credible ability to strike the United States directly with nuclear weapons, this bedrock assumption has been called into question. As this new strategic reality has gradually crystallized, doubts that Washington would actually sacrifice Seattle to save Seoul have called into question the United States’s promise to defend its Korean ally if the North attacked.  

Perhaps not surprisingly, over time, as the South’s sense of insecurity has grown, so too has the sense that something needs to be done to address the North Korean threat. Public and elite opinion alike has long favored a diplomatic solution to the problem of North Korean nukes, pushing for a “comprehensive, verifiable, irreversible (nuclear) disarmament” agreement that would solve the problem once and for all.

In recent years, this has been paralleled by an increasingly widespread sentiment that a stable nuclear balance might be restored if the United States would simply return the tactical nuclear weapons it withdrew from the peninsula as part of a disarmament deal with the Soviet Union in the early 1990s. What has never enjoyed widespread support throughout this period, however, has been the option of Seoul acquiring its own nuclear weapons. 

And then suddenly.

In the last few years this has begun to change dramatically. To begin with, there has been an abrupt shift in popular sentiment. Beginning abruptly in the run up to the 2022 presidential election, South Koreans began to express widespread support for the idea that their country should not merely host U.S. nuclear weapons but should acquire weapons of its own. Indeed, recent public polls suggest that an overwhelming majority of South Koreans now support developing their own nuclear weapons, as opposed to merely calling for the return of U.S. nuclear weapons to their country. 

And this has been echoed by a similar shift in elite opinion, with some officials, like retired Gen. Leem Ho‐​young and National Assembly politician Cho Kyoung‐​tae, now actively promoting the idea.

The reasons for this shift in elite and public opinion are perhaps obvious. North Korea continues to develop its nuclear weapons capabilities, including new delivery systems like solid-fuel ballistic missiles that are easier to move and hypersonic missiles that are more difficult to intercept. And then, of course, there’s the war in Ukraine, which has amplified the fear that, absent an independent nuclear deterrent, countries like Ukraine and South Korea will always be vulnerable to attack by aggressive neighbors — regardless of security “guarantees” like the toothless 1994 Budapest Memorandum or even the Mutual Defense Treaty between Washington and Seoul.

What is less obvious is whether the U.S. will support South Korea acquiring its own nuclear deterrent. Historically, Washington has been opposed to such a development, in part out of a general aversion to the proliferation of such weapons and in part out of a desire to retain the diplomatic leverage afforded by its nuclear patronage over allies and partners in the region.

But there are indications that this too is changing, albeit gradually. As some pundits and even some members of Congress are now asking, if the United States was unwilling to sanction Israel when it went nuclear, and if it quickly acquiesced when India and Pakistan did the same, would it seriously oppose Seoul’s development of an independent nuclear deterrent?

And what happens if, with or without the United States’s blessing, Seoul does suddenly develop and deploy nuclear weapons of its own? Two possibilities. On the one hand, such a development might usher in an age of stability (if not exactly peace and harmony) based on mutual assured destruction. Imagine the Soviet-American nuclear relationship during most of the Cold War, but on a peninsular scale.

On the other hand, it might heighten the North’s sense of vulnerability and insecurity, generating endless nuclear crises, any one of which could spiral out of control and end with a general nuclear war. Imagine the Soviet-American nuclear relationship during the Cuban Missile Crisis.

Let’s hope that if South Korea does decide to go nuclear, the former scenario comes to pass. For if not, well, that’s how the world ends – first gradually, then suddenly.

Andrew Latham is a professor of international relations at Macalester College in Saint Paul, Minn., and a non-resident fellow at Defense Priorities in Washington, D.C. Follow him on Twitter @aalatham.