North Korea’s nuclear threat is increasing day by day, and South Korea’s security is getting more and more precarious. In these circumstances, it is fortunate that the United States offers extended deterrence for South Korea’s security. However, it is not clear what assistance South Korea can get and what role South Korea can play regarding extended deterrence.

The South Korean government said that it would respond to the North Korean nuclear threat by establishing a “Three Axis” comprised of a ‘Kill-Chain’ in which South Korea engages preemptively when it detects signs of an imminent North Korean attack; a ‘Korea Air and Missile Defense’ (KAMD) in which South Korea protects itself from North Korean missiles; and Korea Massive Punishment and Retaliation (KMPR) in which South Korea carries its massive retaliation against North Korea if it attacks South Korea. All of these measures, however, are based on conventional military forces and raise questions about whether they could counter a North Korean nuclear threat. That is, it cannot be certain whether the “Three-Axis” system pursued by South Korea is sufficient to counter North Korean nuclear threat. To compensate for this, the United States has decided to make extended deterrence more concrete. And yet it is not clear how the South Korea’s Three-Axis system and the US extended deterrence are interconnected and complementary.

South Korea is particularly anxious because South Korea does not know how the US will respond to the North Korean nuclear threat and with which means, and how South Korea can participate and be consulted when the United States decides to carry out extended deterrence measures.

Although South Korea believes in the US security commitment and its extended deterrence toward South Korea, South Korea cannot be assured because US policies often change from administration to administration. In 1969, President Nixon outlined his doctrine in Guam, saying “…as far as our role is concerned, we must avoid that kind of policy that will make countries in Asia so dependent upon us that we are dragged into conflicts such as the one that we have in Vietnam…as far as the problems of internal security are concerned, as far as the problems of military defense, except for the threat of a major power involving nuclear weapons, that the United States is going to encourage and has a right to expect that this problem will be increasingly handled by, and the responsibility for it taken by, the Asian nations themselves.” This was followed by the withdrawal of the 7th Division of the US Forces in Korea in 1971. It was around this time that South Korea began pursuing self-reliant defense and development of indigenous nuclear weapons. President Carter also pushed for the withdrawal of US troops from South Korea. Hence, it should be noted that whenever the US administration changes, policies can change as well. And South Korea’s security can be shaken; and therefore stable mechanisms are needed to reduce impacts of changes in the US administration. The security situation South Korea is currently facing is no better than when the Nixon Doctrine was announced, and South Korea needs to take minimal measures to protect itself.

It is a common sense in the international community that nuclear weapons can be deterred only by nuclear weapons. Just before the dissolution of the Soviet Union in 1991, the Soviet Union withdrew about 20,000 nuclear weapons from Europe, and the United States withdrew 6,000 tactical nuclear weapons that had been deployed throughout the world, including those in South Korea. The United States had deployed more than 900 tactical nuclear weapons in South Korea at its peak, and by 1991, the United States had about 100. It is estimated that North Korea currently possesses at least 30 to 60 nuclear weapons. To protect South Korea and US forces in the country, the United States should consider redeploying at least several dozens of tactical nuclear weapons out of 130 of them stored in the U.S. mainland to the Korean Peninsula. This is consistent with the concept of extended deterrence. The United States currently deploys approximately 100 nuclear weapons in Europe, and has Nuclear Sharing system with Belgium, Germany, Italy, the Netherlands, and Turkey, which allows these countries to participate in the NATO’s planning for the use of nuclear weapons and to carry US nuclear weapons on their aircraft in case of a contingency. It is hard to understand why the case on the Korean Peninsula is different from the case in Europe.

North Korea is an unpredictable opponent. Having failed economically and being only left with nuclear weapons, North Korea can strike South Korea in a surprise attack at any time. For example, if nuclear-equipped North Korea launches a surprise attack and takes by force a small island in the West Sea, South Korea will demand North Korea to withdraw. Then North Korea may threaten to use nuclear weapons against the South, and it is likely that South Korea cannot find proper measures to respond to the North Korean nuclear threat. In such a circumstance, it is questionable whether the United States will actively intervene and support South Korea.

For its survival, South Korea must review whether the US extended deterrence is functioning properly. In the process South Korea has to think first about what it should do. It is questionable whether South Korea is capable of keeping track of North Korean activities in real time. South Korea needs to know beforehand when Kim Jong-Un gives an order to launch missiles against South Korea, to whom Kim Jong-un gives such an order and how his order is relayed. South Korea should also know how long it takes for North Korea to prepare for a launch and how long it takes for missiles to reach South Korean targets, as well as how long it takes for South Korea’s responses to be mounted. However, it seems that is not the case at present. The entire process consists of three-steps: “see, decide, and respond”, and it will be fast paced. In order to properly respond under such circumstances, South Korea needs to consult and carry out the implementation process of extended deterrence with the United States.

When North Korea shows signs of serious provocations, the United States will deploy strategic assets such as B-52 strategic bombers, F-35 stealth fighter aircrafts, and nuclear submarines based in Guam, Hawaii, and Japan near the Korean Peninsula.  It is not known whether the United States is consulting with the South Korean government on the deployment of strategic assets. This is completely different from the case in Europe. In Europe, the Nuclear Planning Group (NPG) was established to discuss and share the operation plans, objectives, and process on the use of nuclear weapons. Such a system also needs to be established for South Korea.

For credible extended deterrence, there must be a concrete plan of how nuclear weapons would be employed under which circumstances. It is unclear whether the United States has such a plan. The United States should formulate a detailed plan for nuclear use. South Korea and the United States must discuss the procedure in which nuclear weapons use would be decided and implemented, as well as to institutionalize such a consultative mechanism.