The Dangers of Decoupling in Northeast Asia

The U.S. security alliances with Japan and the Republic of Korea (ROK) remain two of the most enduring legacies of the postwar global system. Despite dramatic changes in the global security environment, those alliances have continued to offer stability and peace in Northeast Asia and allowed the region to prosper, to the benefit of the United States as well as its allies.

The success of those security alliances was hardly assured. The alliances have been, from their inception, inherently unbalanced. The United States provides a security guarantee that is effectively one-sided, not only when it comes to Japan, with its constitutional restrictions on the use of force, but also with respect to the ROK, which necessarily is largely focused on the Korean Peninsula itself. Of course, our allies have at times contributed to the global security interests of the United States, and the U.S. base structure, particularly in Japan, has a broader regional, if not global, purpose.

But fundamentally, the alliances are seen as a defense of our allies against external threats. And in that regard, the U.S. resolve to provide security has been questioned almost from the inception of the treaties that bind us. There is a persistent fear of abandonment, of a “decoupling” of the United States’ security from that of its allies and a U.S. retreat from responsibility. Such fears arose in Europe during the Cold War and were manifest in Japan in the mid-1960s when China began to test nuclear weapons.

Fear of abandonment increased dramatically in both Japan and the ROK amid the disaster and defeat of the Vietnam War, the Guam Doctrine and the withdrawal of U.S. forces from the region, and the shocking opening to China without notice to our allies. In Japan, there was talk of going nuclear, while the ROK undertook a clandestine program to build a nuclear bomb. The end of the Cold War with the Soviet Union, followed by the withdrawal of tactical nuclear weapons deployed onshore in the ROK and onboard vessels in the Pacific, again revived those concerns.

This fear of decoupling is most powerfully triggered by the threat from nuclear-armed states. The security guarantee rests on the extension of the so-called nuclear umbrella—a public, and private, pledge to use nuclear weapons to deter and, if needed, respond to an attack on U.S. allies. For extended deterrence to be credible, both our allies and our foes must believe that the United States is willing to use nuclear weapons in defense of our allies even if it puts U.S. territory at risk. In popular parlance, the United States must be willing to trade Los Angeles to defend Tokyo or Seoul.

Terence Roehrig’s new book, Japan, South Korea, and the United States Nuclear Umbrella: Deterrence After the Cold War, is far and away the most complete, authoritative, and analytically provocative account of the complex history of these issues written to date. Roehrig, who directs the Asia-Pacific Studies Group at the U.S. Naval War College, begins with an incisive discussion of the doctrines of extended deterrence, explaining that the extension of a nuclear umbrella is a subset of that broader goal and that deterrence can also be provided by conventional means (chap. 1). It is a distinction essential to the policy conclusions he reaches later in the book. Deterrence, as Roehrig explains, rests on two essential assumptions—that the actors are rational decision-makers and that the threats to use force, including nuclear weapons, are credible.

The book goes on to provide a concise account of the history of the nuclear umbrella and extended deterrence during the Cold War in chapter 2, beginning as it should with an account of the legacy of the first use of those weapons against Japan. It moves on in chapter 3 to examine the threats that have reinvigorated the need for extended deterrence, namely China and North Korea. Here, Roehrig makes an essential distinction between the long-term threat posed by China and the near-term threat posed by North Korea. Although China seeks to match...