Are Current U.S. Extended Deterrence Approaches Sustainable?

Terence Roehrig’s Japan, South Korea, and the United States Nuclear Umbrella: Deterrence After the Cold War is a timely addition to the literature on extended deterrence in Northeast Asia. This book is particularly relevant today given that rapidly advancing Chinese and North Korean military capabilities are raising concerns about the viability of U.S. security commitments to Japan and South Korea. Japan, South Korea, and the United States Nuclear Umbrella provides a valuable historical and theoretical primer for scholars and policymakers reassessing U.S. extended deterrence commitments.

Roehrig begins by examining the basics of deterrence theory and discussing the challenges of extending deterrence—nuclear or otherwise—to one’s allies. This summary is clear and concise, differentiating primary deterrence from extended deterrence, immediate deterrence from general deterrence, and symmetric deterrence from asymmetric deterrence. Roehrig also unpacks some of the foundational assumptions of deterrence theory, including rationality and credibility. He then explains how the United States attempted to apply extended deterrence in East Asia during the Cold War. After reviewing the historical record, Roehrig pivots to the modern day and assesses evolving Chinese and North Korean military capabilities, which represent the primary deterrence concerns for the United States and its allies in East Asia. He effectively highlights the fact that the two U.S. allies in Northeast Asia prioritize these threats differently, with Japanese leaders tending to focus primarily on China and South Korean leaders emphasizing North Korea.

Perhaps Roehrig’s most valuable contributions are the book’s fourth and fifth chapters, which concisely summarize the extended deterrence relationships between the United States and Japan and South Korea, respectively. With mounting threats from China and North Korea, extended deterrence dilemmas are drawing greater attention from leaders in all three countries. These chapters provide tidy histories of the evolution of these extended deterrence relationships from the perspectives of Washington, Tokyo, and Seoul and should be required reading for policymakers considering changes to extended deterrence arrangements.

The final two chapters evaluate U.S. extended deterrence and then draw implications for today. These chapters make several core arguments. First, “the nuclear umbrella likely does little to deter anything other than nuclear war” (p. 187). Roehrig does not believe that U.S. extended deterrence threats to use nuclear weapons in response to non-nuclear attacks are credible. As a result, he favors the use of “precise, lethal conventional options” rather than nuclear weapons to “achieve similar strategic effects against North Korea as well as China” (p. 189). Nevertheless, “given the overwhelming power of nuclear weapons, an uncertain umbrella retains value as a deterrent” (p. 193). As a result, Roehrig concludes that “despite these concerns, the nuclear umbrella will be ‘good enough’ when it is part of a strong, credible alliance” (p. 197). Supporters of current U.S. extended deterrence policies will find themselves reassured by this conclusion.

There is much to commend in Roehrig’s appraisal of the choices facing leaders in Washington, Tokyo, and Seoul. Yet three limitations remain. First, the book would benefit from an original theoretical construct that could weave together its various elements. Second, Roehrig may be overly optimistic about the sustainability of current U.S. extended deterrence arrangements. Third, as a result of the first two limitations, the book may leave readers searching for tangible suggestions about how to enhance extended deterrence. Each of these issues is addressed in turn below.

First, although Roehrig’s synthesis of theory and history is detailed and insightful, Japan, South Korea, and the United States Nuclear Umbrella lacks a central puzzle or novel theoretical argument, which limits its contribution to the existing literature. Not all books require a new puzzle or theoretical construct, but treatments without these elements risk restating conventional views. At the outset, Roehrig notes that “the central argument of this book is that the United States does indeed possess a nuclear umbrella that has the capability to protect its allies with nuclear weapons should deterrence fail” (p. 9). This assertion is largely in line with conventional views. Thus, the book may be more appealing as a theoretical and historical primer than for more novel contributions.

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