Hyun-Wook Kim is Professor at the Institute of Foreign Affairs and National Security in Seoul.

Is extended nuclear deterrence dead? It is not easy to answer this question, but my answer is that it is still effective and cannot be ignored.

The first argument concerns providing assurance to allies. South Korea has always been very sensitive to changes in US security policy. After the end of the Korean War, Seoul was shocked by the decrease of US forces in the region, forcing the US to introduce US tactical nuclear weapons to South Korean territory. When President Nixon withdrew US forces from South Korea in 1970s, the South Korean president attempted to develop a domestic nuclear capability. And most recently, when the US Nuclear Posture Review identified a reduced role for nuclear weapons in providing extended deterrence to allies, the response of South Korean elites was very sensitive. Along with the recent North Korean military provocations, there even emerged voices that US tactical nuclear weapons should be reintroduced to South Korea.

As mentioned by Bruno Tertrais, the psychological impact that nuclear weapons possess is very significant. Everybody knows that the actual use of nuclear weapons is an uncommon thing unless it pertains to vital or existential interests of states. But the case of two Koreas belongs to this category.

Why would North Korea pursue nuclear weapons? From the perspective of Western countries, it may be as diplomatic and domestic bargaining chips. But the North Korean position is that its security is tremendously in danger from the US, and that this vital danger pushes the North to develop nuclear weapons. On the Korean peninsula, nuclear weapons are closely tied with vital interests. Living with North Korea as an imminent danger, South Korean vital interests are also under threat, which necessitates the sincere provision of US extended nuclear deterrence.

What I mean by 'sincere' is not just verbal promises but real action by the US. After the first North Korean nuclear test in 2006, more than 67% of South Koreans approved the idea of developing South Korea's own nuclear weapons. With the imminent threat of North Korea, South Korea did not feel secure with the provision of extended nuclear deterrence from the US, which is so remote from South Korea. So the problem does not lie in whether extended nuclear deterrence is needed or not, but whether extended nuclear deterrence can be provided in assured and valid ways.

The second argument for extended nuclear deterrence concerns the credibility of deterring North Korea. The probability that the North would actually use nuclear weapons is very minimal, and most of the skirmishes in the Korean peninsula are limited to the small-scale aggressions like the Cheonan ship sinking and Yeonpyong island military attack. In this vein, George Perkovich argued that the role of non-nuclear deterrence is significant. But still, in this case, the role of nuclear deterrence cannot be ignored.

Recent North Korean military provocations prove that US extended deterrence has failed. Despite ongoing US promulgations of its solid extended deterrence provision to South Korea, North Korea has continued its military provocations because the North knows that the US would not willing to retaliate: the US does not want small skirmishes to be escalated into a large-scale warfare. This implies that the US and South Korea are deterred by the North.

This stalemate necessitates the role of nuclear weapons. All the partners within and surrounding the Korean peninsula are well aware that the risk of using nuclear weapons is very minimal. But it is more about psychological effect and a game of bluff. It is such a game of bluff that made North Korea restless when the US nuclear-powered aircraft carrier George Washington participated in the US-South Korea military exercises near North Korea. Actual use of nuclear weapons is unlikely, but it still retains a psychological deterrent effect.

Cold War strategic stability was maintained by the nuclear strategies of the US and Soviet Union based upon their virtual use of nuclear weapons. Now, it rests more on psychological, if not symbolic, effect.

The Nuclear Reactions column is supported by the Nuclear Security Project of the Nuclear Threat Initiative, as part of a wider partnership between the NSP and the Lowy Institute.

Photo by Flickr user US Army Korea - IMCOM.