The Limited Roles of U.S. Nuclear Deterrence in Northeast Asia

In the era of North Korea’s incessant, and almost successful, attempts to become a nuclear weapons state and the rise of China’s power, Terence Roehrig’s book Japan, South Korea, and the United States Nuclear Umbrella: Deterrence After the Cold War is a very timely and interesting academic work. Bridging theory, history, and contemporary debates, Roehrig delves into the effectiveness of the United States’ security commitment to its two main allies in Asia, Japan and the Republic of Korea (ROK), particularly in the form of nuclear deterrence. The Cold War came to an end almost three decades ago at a global level, but military tensions still remain in Northeast Asia. North Korea’s decision to arm with nuclear weapons and intercontinental ballistic missiles (ICBMs) further destabilizes the region’s geopolitical situation, continuously requiring the deep involvement of U.S. leadership in managing and resolving this new nuclear crisis after the Cold War. Against this backdrop, Japan, South Korea, and the United States Nuclear Umbrella offers readers detailed explanations and invaluable insights on how to view the U.S. role in dealing with the current and future nuclear confrontations in Northeast Asia.

Roehrig provides a well-structured analysis of the U.S. nuclear umbrella for Japan and South Korea by introducing theory, overviewing history, moving to threat analysis and case studies, and then assessing overall U.S. nuclear capability and resolve. Yet missing from the book is a chapter on the comparative analysis of these two alliances in terms of nuclear deterrence. Despite a number of similarities shared by the alliances in dealing with U.S. extended deterrence, there are some clear discrepancies that make Tokyo and Seoul respond differently to Pyongyang’s increasing threats and U.S. reassurances. Roehrig mentions these comparative aspects here and there in various chapters. For instance, he observes that “the U.S. nuclear umbrella had to remain quiet for many years” in Japan and “provided reassurance only for its leaders,” mainly due to “domestic political sensitivities” and the “nuclear allergy” in Japanese society (p. 63). In comparison, U.S. tactical nuclear weapons in South Korea “were viewed more as an actual warfighting tool than a deterrent” in the early years (p. 63). The withdrawal of those tactical nuclear weapons from the Korean Peninsula in 1991 and the end of the Cold War do not appear to have significantly changed South Korea’s views on nuclear weapons, though. Roehrig notes that “a majority of South Koreans believe developing their own nuclear weapons is a necessary response to North Korea’s nuclear weapons” (p. 152). A single independent chapter or section that more systematically compares the U.S.-Japan and U.S.-ROK nuclear umbrellas and thoroughly reflects on the implications suggested by the similar or different aspects would have been useful.

One of the sticking points in debates about the U.S. nuclear umbrella, which is also the main question of this book, is the issue of credibility: “Would the United States truly be willing to use nuclear weapons in defense of an ally?” (p. 2). Roehrig concludes that the United States is highly unlikely to use nuclear weapons to defend its allies because this is “not in the [U.S.] strategic interest and should be avoided at all costs” (p. 189). Rather, “the nuclear umbrella vis-à-vis North Korea is more important as a message of reassurance for U.S. allies than a tool that adds further to an already stable strategic situation” (p. 186) and has a significant “function for U.S. efforts to stem the proliferation of nuclear weapons” both regionally and globally (p. 196). As Roehrig states a number of times in the book, the U.S. nuclear umbrella offered to South Korea and Japan has been successful in persuading these two allies to remain non-nuclear thus far, which means that U.S. extended deterrence is still regarded as credible by Tokyo and Seoul. However, it is also true that the rapidly changing security environment in Northeast Asia, which was further exacerbated by North Korea’s November 2017 test of an...