Uncertainties in the North Korean Nuclear Threat

North Korea has been very successful in denying the United States and others information about its nuclear weapon program. The result is a high degree of uncertainty about the size and character of the North Korean nuclear weapon threat, how it might be used, and what impact it might have. This briefing addresses those uncertainties. Estimates of the number and nature of North Korean nuclear weapons depend heavily on how much external help the program has received; there is some evidence that help has included the provision of fissile material and assistance in the design of nuclear weapons, including miniaturization for ballistic missiles. North Korea uses its nuclear weapons actively in peacetime for deterrence and to obtain leverage. It could use them heavily in a war. If its force is as large as the uncertainties suggest it might be, North Korea could establish its nuclear weapon capabilities and intent to use them from early on in a war. Like other countries that have developed small nuclear forces, North Korea could threaten adversary cities (mainly in Japan and the Republic of Korea) to control escalation and the developments in a war, striving for some hope of victory. If North Korea actually attacked a city such as Seoul with a nuclear weapon, it could result in hundreds of thousands of casualties, as well as serious damage to the South Korean economy.