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Home > Publications > Research Papers > > Chapter 6: On Rethinking Extended Deterrence
Shared Responsibilities for Nuclear Disarmament: A Global Debate

Chapter 6: On Rethinking Extended Deterrence

Yukio Satoh

The concept of deterrence, let alone that of extended deterrence, needs to be redefined in a new light. Reducing the role of nuclear weapons in deterrence strategy should be pursued for the sake of nuclear disarmament.

However, from the perspective of an American ally in Northeast Asia, the proposed “rethinking of extended deterrence” must be addressed in a much broader security context than the “conceptual framework” Scott Sagan proposes in his stimulating article, “Shared Responsibilities for Nuclear Disarmament.” At the very least, consideration must be given to (1) the regional security conditions surrounding alliances, (2) the present level of strategic consultations within alliances, and (3) the long-term prospects of the changing strategic balance between the United States and its allies, on one side, and its strategic rivals, on the other.

This underlines the importance of a regional rather than a global approach to rethinking extended deterrence, for, on all these subjects, the tasks and priorities for U.S. alliances in Northeast Asia are different, for example, from those for NATO. In contrast to Europe, where the end of the Cold War has remarkably reduced the threat of nuclear weapons, Asia has been witnessing nuclear weapons proliferation during the past two decades.

For Japan and South Korea, deterring North Korean aggression while pursuing the goal of a nuclear-free Korean Peninsula is the top security requirement at present. U.S. extended deterrence is essential to that end. The U.S. government has long been firm in assuring its Asian allies of its commitment to deterrence, and President Barack Obama’s assurances have been unequivocal. In a speech during his first official visit to Tokyo in November 2009, President Obama stated: “So long as these [nuclear] weapons exist, the United States will maintain a strong and effective nuclear deterrent that guarantees the defense of our allies—including South Korea and Japan.”1

What is equally important for the credibility of the U.S. commitment is not now to change the U.S. declaratory deterrence strategy. No-first-use arguments are plausible in the context of nuclear disarmament. In the eyes of those depending on U.S. extended deterrence for their security, however, Washington’s policy of not excluding the possibility of first use of nuclear weapons is essential for the credibility of U.S. extended deterrence. Politically, too, a unilateral change in the U.S. declaratory strategy in the face of North Korea’s tenacious pursuit of nuclear weapons and missile development would only encourage Pyongyang. Moreover, it would be unwise at this time to limit the purpose of retaining nuclear weapons solely to deter nuclear threats.

It is indeed questionable whether nuclear weapons are suitable to deter the threats posed by biological or chemical weapons. Nevertheless, it is also true that no assured means are available for deterring the use of non-nuclear weapons of mass destruction (WMD) such as biological and chemical weapons. In this strategic dilemma, it is inadvisable to exclude the possibility, debatable as it might be, that countries such as North Korea suspected of possessing these WMD would refrain from their use for fear of being punished with nuclear retaliation.

Contrary to the assertion made by Sagan in his article, I have never “recommended that the United States should now threaten to retaliate with nuclear weapons if North Korea uses chemical or biological weapons in any future conflict.” At the 2009 conference organized by the Carnegie Endowment for International Peace, I stressed the need for ambiguity in coping with the threats of biological and chemical weapons, underscoring the distinction between the option of openly rejecting the use of nuclear weapons in response to a biological or chemical weapons attack and that of not saying anything about the point, keeping those to be deterred in suspense. At that conference, I simply noted that “without credible means for deterring the use of biological and chemical weapons, it would be too early to limit the purpose of nuclear deterrence solely to deterring the use of nuclear weapons. This is particularly true for Northeast Asia, where North Korea is suspected to possess both biological and chemical weapons.”2

It must also be pointed out that the Japanese government’s pronounced policy of relying on the U.S. nuclear deterrent to protect the country “against the threat of nuclear weapons” was originally formed as part of the first Defense Program Outlines adopted in 1976, when the so-called sole purpose of nuclear weapons was not the question at issue. As I noted in my Carnegie conference presentation, Tokyo and Washington announced in 2007 that “both nuclear and non-nuclear strike forces and defense capabilities” of the United States formed the core of extended deterrence, without specifying the object of this deterrence. I believe that the planned revision of the official Defense Program Outlines should reflect this line of thought.

On the other hand, Sagan arguably proposes that “those U.S. allies that remain concerned about conventional or chemical and biological threats to their security should . . . help to develop the conventional forces and defensive systems that could wean themselves away from excessive reliance on U.S. nuclear weapons for extended deterrence.”

Although Sagan’s depiction of the allies’ reliance on U.S. nuclear weapons as “excessive” is his own, Japan-U.S. defense cooperation has already been progressing in the direction he suggests. Strengthened cooperation in the deployment and development of missile defense systems against North Korean missiles is a case in point. Japan-U.S. defense cooperation will no doubt become increasingly important, particularly as the role that advanced conventional weapons systems play in the deterrence strategy is expanded. Japanese efforts to rectify long-recognized deficiencies in sharing responsibilities under the Japan-U.S. Security Treaty are required more than ever.

This leads to the second subject that must be taken into consideration in rethinking extended deterrence: the level of strategic consultations within alliances. Unlike NATO, the Japan-U.S. security arrangements lack a mechanism for consultations on nuclear strategy, as does the South Korea-U.S. alliance, so far as I understand. The Japanese case is more conspicuous, for the government has long been reluctant to be involved in U.S. nuclear strategy. The public’s strong anti-nuclear-weapons sentiment is behind this.

It has therefore been an epoch-making development that the Japanese and U.S. governments have, since 2009, begun to explore ways to commence consultations on extended deterrence. As of this writing, though, the alliance has not overcome the unprecedented jolt caused by the widely reported clumsiness of the new coalition government led by Prime Minister Yukio Hatoyama of the Democratic Party of Japan in trying to undo (without proposing any feasible alternative) the long-agreed plan to relocate the U.S. Marine Corps air station from Futenma, Okinawa—a goal central to the 1996 agreement to reduce burdens on local communities caused by the U.S. force presence on the island. It is crucial that the two governments, particularly the Japanese, make every effort to put alliance cooperation back on the right track and pursue their alleged purpose of “deepening” alliance relations through the year 2010, which marks the fiftieth anniversary of the current Security Treaty.Closer consultations on how to facilitate the functioning of U.S. extended deterrence should be an important part of deeper alliance cooperation.

In the absence of a bilateral agreement on secrecy protection as required by U.S. law, Tokyo-Washington consultations on nuclear strategy will not reach the level of NATO’s Nuclear Planning Group. Nevertheless, there are many issues that the two governments can and must discuss below that level, particularly prospective changes in the roles of nuclear and non-nuclear weapons in the U.S. deterrence strategy and, subsequently, required Japan-U.S. defense cooperation for common deterrence purposes. The declaratory part of the U.S. deterrence strategy should also be an important agenda item for such consultations.

Another important step is to link Japan-U.S. consultations on extended deterrence with those between South Korea and the United States. Organizing a trilateral mechanism for strategic consultations would not be diplomatically advisable, for it might make China and Russia unnecessarily suspicious and further harden North Korea’s stance. Given the common interest of Japan and South Korea in enhancing the credibility of U.S. extended deterrence, though, the time has come for the two countries to begin to coordinate their efforts to that end, at least through a set of three bilateral consultations: Japan-U.S., South Korea-U.S., and Japan-South Korea.

Finally, the implications of reductions in U.S. and Russian nuclear stockpiles for U.S. extended deterrence will have to be assessed carefully, as progress in this area would eventually affect the nuclear force balance among the United States, Russia, and China. Russia and China are no longer adversaries of the United States and its allies. Still, the two countries remain causes for concern, particularly for U.S. allies in Asia, because of the dictatorial nature of their regimes and the aggressiveness increasingly seen in their external postures. The continued growth of China’s military power and its lack of transparency are yet other causes for concern in the Asia-Pacific region. Moreover, a bilateral nuclear force balance that Washington would regard as acceptable in relations with Moscow and Beijing might not be reassuring enough to U.S. allies in Asia in the context of the credibility of U.S. extended deterrence.

This issue would perhaps not draw attention before U.S. and Russian nuclear stockpiles each approach the one thousand level. Yet it must be seen as an important subject for consideration in rethinking extended deterrence between Tokyo and Washington as well as between Seoul and Washington, and, one hopes, among all three.


1. Remarks by President Barack Obama at Suntory Hall, Tokyo, on November 14, 2009; http://www.whitehouse.gov/the-press-office/remarks-president-barack-obama-suntory-hall.

2. Panel transcript “Are the Requirements for Extended Deterrence Changing?” Carnegie Endowment for International Peace, April 6, 2009, http://www.carnegieendowment.org/files/npc_extended_deterrence1.pdf.