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.
South Korea by comparison cannot produce plutonium due to a legal agreement with the U.S., which has become a contentious issue in recent years. Seoul wants full control of its civilian nuclear program, but the U.S. has been loath to revisit the agreement, as it opens the door for South Korea to create its own plutonium stockpile. Seoul also has built a satellite launch vehicle that could double as an Intercontinental Ballistic Missile (ICBM).
In society and the political sphere, South Korea does not have the same aversion to nuclear weapons as Japan. A survey conducted in South Korea after North Korea’s fourth nuclear test showed that around 55 percent of South Koreans wanted their country to develop its own nuclear deterrent. Conversely, a 2009 poll in Japan showed that only 24 percent of Japanese wanted to repeal the laws that prohibited its development of nuclear weapons.
Sentiments among politicians exhibit a similar trend. While outspoken South Korean politicians, like Chung Mong Joon and Won Yoo Chel, advocate for nuclear weapons to defend against North Korea, the Park administration has shown no inclination towards weapons development. In Japan the discourse is more reserved and equally against weapons development. A former Japanese cabinet member remarked that “[Japan] will not seek to produce nuclear weapons, but possessing advanced technology and plutonium shows other nations that our country can produce them whenever it wants. This is tantamount to a certain measure of deterrent power.”
For U.S policymakers, the technical abilities and domestic conditions need to be placed in context in order to identify shifts towards nuclear proliferation. Former chief of analysis for the CIA Nonproliferation Center, Torrey Froscher, made clear to The Cipher Brief that “there is no reason to suspect that [either country] is evading its obligation to forgo nuclear weapons,” but the latent capacity of either country cannot be ignored. Thomas Cynkin, a former U.S. diplomat in Japan added that close observation of political and technological developments is important to keeping abreast of any changes in how either country views a homegrown nuclear weapons program.
Both Froscher and Cynkin agree that U.S. interest and involvement in regional security are essential to sustaining non-proliferation in East Asia. An important lesson from the Cold War that still underpins strategic thought on nuclear weapons was that a nuclear deterrent is ineffective without a credible show of intent. Just as deterrence without intent is an ineffective display to one’s enemies, assurance without resolve is an ineffective gesture to one’s allies. Therefore, the U.S. cannot afford to allow Tokyo or Seoul to doubt its nuclear umbrella. In that regard, U.S. Ambassador to South Korea Mark Lippert was quick to shoot down Trump’s assertion that South Korea takes care of its own security by developing nuclear weapons. Lippert called the alliance between the U.S. and South Korea “one of the premier military alliances in the world.” Maintaining the trust implicit in Lippert’s message could be the U.S.’s strongest hedge against nuclear proliferation in East Asia.
Will Edwards is an International Producer with The Cipher Brief.