The Dilemma of Having Two Nuclear Koreas

A missile is launched during a long and medium-range ballistic rocket launch drill

South Korea would gain an appealing symmetry with the North through nuclear weapons—but likely would never use them.

It was probably inevitable that South Korea would entertain the development of nuclear weapons in the face of North Korea’s relentless push for them itself. That conversation is now increasingly widespread on TV and in the media here. Unsurprisingly, conservatives are calling for it; they have for awhile. But other, more moderate voices are kicking it around too, and television pundit shows are filled with this now. An alternative to this is the demand to bring American tactical nuclear weapons back to South Korea. A debate that has been on the fringe of South Korean political life for decades is now having its most robust public discussion ever. For the first time, a clear majority of South Koreans want this capability.

Nuclear weapons are appealing for obvious reasons. They offer an attractive symmetry with now-nuclear North Korea. Nuclear weapons signal global prestige to others, as well as a seriousness and weight in international relations. On the peninsula, they might create a more robust perception of mutually assured destruction (MAD) between South and North Korea. MAD is the notion that two hostile nuclear powers can nonetheless live in a cold peace, because they mutually deter one another with the threat of massive retaliation. South Korea already enjoys MAD in a sense because of the American nuclear umbrella. The United States extends nuclear deterrence to the South. It threatens to strike North Korea with nuclear weapons if North Korea were to do so to South Korea.

But this ‘borrows’ American nuclear weapons, rather than placing them directly under the command of the South Korean president. Despite the tightness of the U.S.-South Korean alliance, local control of such powerful weapons will always be deeply attractive to any sovereign state. And now that North Korea might be able to strike U.S. cities with nuclear weapons, there is a burgeoning debate over whether the United States will ‘risk San Francisco for Seoul.’ That is, if North Korea were to attack South Korea and simultaneously threaten the United States with nuclear attack if it joined the war, would the United States, in fact, join? Much the same debate took place throughout the Cold War. After the Soviets ranged the continental United States with missiles, the European allies became anxious enough about America’s commitment that two of them—Great Britain and France—went nuclear themselves. This same logic appears to be playing out in South Korea, and possibly Japan.

So far, the South Korean liberal administration has rejected this effort, and the U.S. government too has been cool to either proposal—indigenous South Korean nuclearization, or the return of U.S. small nukes to the peninsula. Both sides fear that Southern nukes would just add to the panic and help justify the North’s program and Chinese foot-dragging about it. But there is another important reason why South Korea does not need nuclear weapons: South Korea is unlikely to ever use them against North Korea, even it is nuked by it.

In a scenario so extreme that Seoul was seriously considering nuking North Korea, South and North Korea would be on the verge of, if not already in, a final death struggle to control the peninsula. That is, they would already likely be at war before South Korea even considered such a dramatic option. But in a final war between North and South, South Korea (and the United States) would imminently invade North Korea, which would in turn make South Korea responsible for the blast zones and chaos nuking North Korea had just created. South Korea’s wartime goal of destroying and absorbing North Korea—especially, ironically, if North Korea had nuked South Korea—makes it a bad idea to counter-nuke the North because occupation, including inheriting North blast zones, would happen shortly afterward.