
Following North Korea’s most recent nuclear test on February 12th, conservative officials in the South have resumed calls for the return of U.S. tactical nuclear weapons to the peninsula.

“The only way to defend our survival would be to maintain a balance of terror that confronts nuclear with nuclear,” said Representative Shim Jae-cheol at a National Assembly meeting, before recommending the redeployment of nonstrategic nuclear weapons (NSNWs) to his country. Meanwhile other officials have recommended an independent South Korean nuclear deterrent.

These calls from ROK conservatives may not come as a surprise: Similar exhortations followed previous North Korean provocations. What’s more, this latest iteration of North Korean bellicosity has included some especially ominous rhetoric. DPRK officials have suggested that U.S.-ROK joint military exercises could ignite a war, and that South Korea may meet its “final destruction.”

There is no question that the South has reason to be anxious regarding its security. But this latest round of security challenges on the peninsula begs the question: Why do some South Koreans want tactical nuclear weapons, and what would they do for ROK security? Specifically, how would they reinforce the U.S. nuclear umbrella?

American tactical nuclear weapons were withdrawn from the Korean peninsula in late 1991 as part of President George H.W. Bush’s Presidential Nuclear Initiative. Shortly thereafter, the ROK and DPRK signed a Joint Declaration of commitment to a nuclear weapons-free Korea. The North’s subsequent development of a small, independent nuclear stockpile upended that agreement. The DPRK also maintains that the ROK’s continued alliance with the United States violates the pact, as the South remains under the U.S. nuclear umbrella. If the South were the victim of a major attack, the United States could defend it using its strategic nuclear arsenal of homeland-based intercontinental ballistic missiles (ICBMs),bombers and sea-based submarine launched ballistic missiles (SLBMs).

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It is not surprising that many in the South feel that they have gotten short shrift as the North has continued to develop nuclear and missile capabilities: After agreeing to the withdrawal of U.S. NSNWs, they now face a nuclear-armed, highly-provocative neighbor to the North. And despite the fact that the United States goes to great lengths to assure the ROK of its continued conventional and nuclear commitment to its security, there is skepticism in the South as to whether American nuclear assistance would be forthcoming in a time of crisis. In a 2012 Asan Institute survey, only 48 percent of South Korean respondents said that they believed the United States would employ its nuclear forces in response to a nuclear strike by the DPRK on South Korea. A significant number of South Koreans, including high-level officials seem to believe that the return of NSNWs would help to fill this perceived strategic gap.

One reason for continued South Korean interest in tactical nuclear weapons is their role in so-called “de-coupling.” In any alliance that involves extended nuclear deterrence, there is a fundamental credibility problem: Why would a nuclear state like the United States use those weapons on behalf of South Korea, and invite retaliation on its own homeland? Put differently, why would an American president ever voluntarily trade Washington for Seoul? For the time being, the DPRK probably doesn’t have the missile capabilities to reach the continental United States. If it acquires them, however, and the North actually has the ability to hold U.S. cities at risk, this dilemma could be of even greater concern.


Some believe this dilemma is exacerbated by the fact that the U.S. nuclear umbrella commitments to the ROK relies entirely on homeland and sea-based deterrents. If there were a small number of tactical nuclear weapons on the peninsula and the ROK was the victim of a DPRK attack, the United States could authorize nuclear use without assuming automatic retaliation against its own cities. This might, in turn, make nuclear use in a crisis more likely, and therefore, the umbrella more credible.

Another reason for South Korea’s interest in the return of tactical nuclear weapons is the role that they might play as a bargaining card against the DPRK’s small stockpile. In the many cycles of negotiations that have taken place since the North began its nuclear program, the South has not had as much bargaining leverage as it might have wanted. It retains the option to cut or halt food aid to the North, withholding a “carrot,” but this aid has widespread domestic political support in the ROK. Reintroducing tactical nuclear weapons could serve as a “stick” to be traded away if the DPRK becomes willing to relinquish its own nuclear weapons.

The decoupling and bargaining rationales are not merely academic, but have resulted in significant popular support for the return of NSNWs. A February 2013 Asan poll found that 67 percent of respondents supported the return of U.S. tactical nuclear weapons. Moreover, these sentiments are not just a reaction to the recent DPRK test: A June 2012 poll also found that 69 percent of respondents favored NSNW redeployment. But the question remains: Would tactical nuclear weapons really strengthen the U.S. nuclear umbrella?

Extended deterrence, as conceived of throughout the Cold War, aims to prevent large-scale conventional or nuclear attacks on allies with the threat to use nuclear weapons on their behalf. Despite the inherent credibility problem, American extended deterrence appears to have a strong empirical record: No U.S. ally that holds a formal security guarantee has ever been the victim of a major attack. One cannot argue that this is directly causal, as successful deterrence is very difficult to measure. Nonetheless, the basic point holds that extended deterrence aims to protect allies’ vital interests, and those do not appear to be under assault.

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The problem, at present, is not that the American commitment to fight a major war on behalf of an ally has weakened. Rather, it is that U.S. allies like South Korea have become subject to lower-level provocations that are very difficult to deter indeed. The U.S. nuclear umbrella is not necessarily designed to forestall nuclear weapons testing, or to dissuade the sinking of a frigate or the shelling of offshore islands. Yet when these acts occur, South Koreans feel fundamentally insecure.

This problem is not exclusive to the U.S.-ROK alliance. The recent Sino-Japanese standoff over the Senkaku/Diaoyu Islands has also raised the question of how extended deterrence functions at lower levels of escalation. It remains highly unlikely that the United States will ever have to decide whether or not to use nuclear weapons on South Korea’s behalf. China’s rise and North Korea’s continued nuclear and missile developments make it quite probable, however, that lower-level incidents will continue to surface, provoking anxieties from allies who feel that the U.S. umbrella is not water-tight. The return of tactical weapons may make some South Koreans feel that American nuclear use on their behalf is modestly more likely, but it will not solve the puzzle of how to shore up deterrence at lower levels of conflict.

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South Korean calls for the return of NSNWs should not be dismissed, but taken as a signal that further assurance from the United States is needed. Whether through the recently established U.S.-ROK Extended Deterrence Policy Committee or other channels, the alliance must make coordination around lower-level threats a top priority. A failure to do so could result in serious alliance divisions when crises do arise, and only exacerbate feelings of insecurity in Seoul. Extended deterrence doubts could also have regional reverberations if they result in a more robust South Korean nuclear program.

There are, however, several reasons for optimism: The U.S.-ROK alliance will soon celebrate its 60th anniversary, and has weathered many a storm since its founding. The alliance has maintained cohesion despite several recent challenges, including three DPRK nuclear tests, numerous missile launches, the sinking of the Cheonan, and shelling of Yeonpyeong. At 95 percent, South Korean popular support for the pact could scarcely be higher. In light of these facts, the United States and ROK should commit to finding new and innovative defense and deterrence solutions to deal with lower-level conflict. The redeployment of tactical nuclear weapons to the Korean Peninsula is a Cold War solution to a 21st century problem.

Mira Rapp-Hooper is a doctoral candidate in political science at Columbia University where she is completing a dissertation on extended deterrence and alliance politics