Nuclear Deterrence and Assurance in East Asia

Among Republican frontrunner Donald Trump’s array of foreign policy positions is the suggestion that South Korea and Japan develop nuclear weapons for their own security so the U.S. would not have to take responsibility for their protection. While national security experts responded that Trump’s view was nearsighted and would be counterproductive for regional stability, the comment did highlight a longstanding and controversial security question for Japan and South Korea: can they trust the U.S. nuclear umbrella, and if not, will they develop their own nuclear deterrent? North Korea, the primary reason Japan and South Korea need a deterrent, continues to exacerbate the issue with its continued nuclear and missile tests. For U.S. policy makers, it is important to understand where these countries stand on nuclear weapons and what their capabilities are to create nuclear weapons in order to balance a non-proliferation policy with regional security.

Japan and South Korea display varying degrees of nuclear latency, that is not having nuclear weapons but possessing the technological acumen and resources to quickly create them for national defense. Between the two countries, Japan exhibits a much higher degree of nuclear latency. It has full control of its nuclear fuel cycle, meaning it is not prohibited from producing plutonium, a fissile material, in its civilian reactor; its satellite launch vehicles are large enough to carry a nuclear warhead; and it has a domestic plutonium stockpile amounting to nearly 10 tons, which by one estimate is enough for 1,000 weapons.