The most prominent feature distinguishing U.S. nuclear strategy is extended nuclear deterrence. Unlike other countries, the United States does not seek to use its nuclear weapons simply to deter attacks against itself, but, rather, attempts to protect the entire free world. It provides a nuclear umbrella to more than 30 formal treaty allies in Europe and Asia, and arguably to others as well. In a new book, Japan, South Korea, and the United States Nuclear Umbrella, Terence Roehrig explores the U.S. nuclear security guarantee to two important treaty allies in East Asia, Japan and South Korea.
This is not a typical political science book that lays out a theory and then tests it against alternative explanations in a series of empirical studies. Rather, Roehrig is speaking to those who wish to better understand a prominent feature of the contemporary international security environment and helps to inform them on the issue by bringing to bear theory, history, and policy analysis.
The book is logically structured. Roehrig reviews deterrence theory as it relates to extended nuclear deterrence and chronicles the development of the history of the nuclear umbrella in East Asia during the Cold War. Next, he analyzes the threats against which the umbrella is aimed, China and North Korea. Then he turns to contemporary issues involved with extended nuclear deterrence in Japan and South Korea. Finally, he analyzes U.S. strategy and capabilities and concludes with the implications of his arguments for the future of U.S. policy.
Roehrig demonstrates a masterful command of the major issues and a subtle appreciation of the nuance of these cases. He expertly discusses, for example, the different threat perceptions of U.S. regional allies and the complications they pose for American strategy. While Washington and Tokyo perceive threats from both a rising China and a nuclearizing North Korea, the United States—South Korea alliance is focused almost exclusively on the threat from North Korea. Seoul wants to maintain constructive diplomatic and economic relations with Beijing and is wary about getting pulled into an anti-China alliance. Moreover, Roehrig discusses the difficulty of forging closer trilateral relations among America and its allies in Asia, given the antipathy between Japan and South Korea due to historical grievances over imperial Japan’s occupation of the Korean Peninsula before and during World War II.
While not aiming to advance a new theory, the book does contain a central argument, and it is a provocative one. Roehrig maintains that the U.S. nuclear umbrella serves a critical role in East Asian alliance management and for the regional security architecture. Here, Roehrig is on solid ground; there is strong bipartisan support for this position in the Washington foreign policy community.
The author continues, however, with a more controversial judgment. He argues that it is highly unlikely, and would indeed be unwise, for the United States to ever actually use its nuclear weapons to defend these allies, even in response to an enemy nuclear attack. He maintains that this is because a U.S. nuclear response would have devastating consequences (such as radioactive fallout) for friends and foes alike and would weaken the global norm against nuclear nonuse, and because the United States has plenty of conventional military response options.
Many readers will sympathize with Roehrig’s argument. After all, nuclear weapons have not been used since 1945. Scholars have written about the taboo against nuclear weapons use. And less than a decade ago, U.S. President Barack Obama made the global elimination of nuclear weapons a central pillar of his foreign policy platform. Many will therefore find it difficult to imagine a U.S. president ordering a future nuclear strike in East Asia.
Many others, including the author of this review, will disagree, however. If the U.S. nuclear umbrella is nothing more than an elaborate bluff, then there is little reason for it to deter enemies or to assure allies. Indeed, this leads to a tension in Roehrig’s central argument: How can the U.S. nuclear umbrella be an important tool of alliance management and regional security if it is all just pretend?
Moreover, there are strong counterarguments to Roehrig’s rationale for U.S. nuclear restraint. If North Korea uses a nuclear weapon, for example, would the international community simply wait for Kim Jong Un to launch a second or a third nuclear attack? It would be irresponsible for policymakers and politicians to needlessly expose their citizens to this danger, and many in Washington and allied capitals would advocate that the United States act immediately to do whatever it can to disarm North Korea and prevent follow-on nuclear attacks. Given the size and scope of North Korea’s growing nuclear and missile program and Pyongyang’s well-known efforts at hiding and hardening its capabilities, it is unlikely that this mission could be accomplished in a prompt manner with conventional forces alone.
Furthermore, and perhaps paradoxically, failing to use nuclear weapons in response to a nuclear attack may be fatal for the norm of nuclear nonuse. If the United States or its allies suffer a nuclear attack and the United States does not respond in kind, it could send the message that America is unwilling to use its nuclear weapons. U.S. adversaries may learn that they can employ nuclear weapons without fear of a U.S. response. This could incentivize enemy nuclear-weapons proliferation and additional nuclear attacks in the future. U.S. allies may draw the lesson that they need to build independent nuclear arsenals if they hope to have an effective deterrent. On the other hand, a nuclear response to a nuclear attack could restore the deterrence of enemies and the assurance of U.S. allies.
Roehrig’s conclusion may have been more persuasive just a few years ago, but nuclear weapons have returned to the center of international politics. North Korea is on the verge of becoming only the third U.S. adversary with the ability to deliver nuclear warheads to the continental United States. The 2018 National Defense Strategy of the United States identified the return of great-power competition with China as a foremost threat to U.S. national security, and China is expanding and modernizing its nuclear arsenal. For the first time since the end of the Cold War, the 2018 U.S. Nuclear Posture Review placed renewed emphasis on U.S. nuclear weapons, calling for a strategy and new capabilities for limited nuclear war.
While I share Roehrig’s hope that the United States will never have to use nuclear weapons again, I believe that this will only happen if the United States persuades its adversaries that it is fully prepared to do so if necessary in extreme circumstances. Donald Trump’s recent claim that North Korea “will be met with fire and fury, and frankly power the likes of which this world has never seen before” should it make threats against the United States would appear a rather clear attempt to signal American willingness to use nuclear weapons under certain circumstances. Of course, whether it is wise to suggest such an act on the basis of “threats” alone, rather than only after a devastating attack by an adversary, is another matter entirely.
Again, many (and maybe even most) readers in the academy will side with Roehrig in this policy judgment. But regardless of where one comes down on this debate, there is no doubt that Japan, South Korea, and the United States Nuclear Umbrella provides a thorough and thought-provoking resource for readers interested in better understanding America’s nuclear alliance commitments in East Asia.
The author would like to thank Andrew Park for invaluable research assistance in preparing this review.
