	Introduction

The Bush Administration described the strategy of "tailored deterrence" to define the role that nuclear weapons might play in U.S. national security policy. Yet, there has been little discussion of this concept, either in Congress or in the public at large, that would allow this concept to serve as a mechanism to help determine the size and structure of the U.S. nuclear force. This absence of discussion has also made it difficult to identify the ways in which tailored deterrence differs, if at all, from the Cold War concept of strategic deterrence and how it might alter the role of nuclear weapons in U.S. national security strategy. It then identifies a number of issues that Congress might address when it reviews these differences, including the question of whether detailed and tailored attack plans are more likely to enhance deterrence or more likely to lead to the early use of nuclear weapons, and the question of whether tailored deterrence provides any guidance about the future size and structure of U.S. nuclear forces. From the end of World War II, and, particularly, from the first explosion of a Soviet nuclear weapon in 1949, until the end of the Cold War in 1991, the United States relied on nuclear weapons to deter Soviet aggression and forestall the outbreak of a global war between the United States and the Soviet Union. This widespread consensus about the nature of the threat to the United States and its allies, and the need for nuclear weapons to deter and respond to this threat, began to dissolve during the 1990s, after the demise of the Soviet Union. Although the Obama Administration has not yet completed its nuclear posture review or enunciated a role for nuclear weapons in U.S. national security strategy, reports indicate it will continue to focus on the emerging threats from nuclear proliferation, weapons of mass destruction, and the possible use of a nuclear weapon by non-state actors. Specifically, and of interest for this report, the Defense Department identified the need to shift "from 'one size fits all' deterrence to tailored deterrence for rogue powers, terrorist networks, and near-peer competitors." But, even during the Cold War, the United States tailored its nuclear targeting doctrine, its nuclear weapons employment policy, and its nuclear force structure to enhance or maintain the credibility of its nuclear deterrent posture. Questions about the credibility of the U.S. deterrent posture persisted throughout the Cold War, with the United States adjusting its doctrine, targeting strategy, and force structure periodically in an effort to bolster its credibility and enhance deterrence. After the collapse of the Soviet Union, the Department of Defense conducted several studies to review U.S. nuclear targeting strategy and weapons employment policy. Nuclear weapons threaten destruction of an adversary's most highly valued targets.... The new nations challenging the United States may not possess nuclear weapons at all, and certainly will not possess the capability to destroy the United States as a functioning society. Nevertheless, these differing perspectives on both the substance and the rationale for U.S. nuclear weapons, in general, and tailored deterrence, in particular, give rise to several specific issues, addressed in the remainder of this report, that might be part of a congressional, or even national, debate on the future role of nuclear weapons in U.S. national security policy. The 111 th Congress may also address questions about the role of nuclear weapons in U.S. national security strategy when it reviews the results of the Obama Administration's nuclear posture review, which is due to be completed early in 2010. How Much Has Nuclear Strategy Changed? There is no question that the Bush Administration changed the rhetoric about U.S. deterrent strategy and the role of nuclear weapons in that strategy substantially when it released the nuclear posture review in late 2001. Further, just as U.S. war plans evolved during the Cold War to accommodate changes in weapons capabilities and threat assessments, the Bush Administration's supporters argued that tailored deterrence would allow for similar, ongoing modifications to U.S. war plans.
The Bush Administration outlined a strategy of "tailored deterrence" to define the role that nuclear weapons play in U.S. national security policy. There has been little discussion of this concept, either in Congress or in the public at large. This leaves unanswered questions about how this strategy differs from U.S. nuclear strategy during the Cold War and how it might advise decisions about the size and structure of the U.S. nuclear arsenal.
Throughout the Cold War, the United States relied on nuclear weapons to deter an attack by the Soviet Union and its allies and to forestall the outbreak of a global war between the United States and the Soviet Union. However, the broad Cold War-era agreement about the role of nuclear weapons in U.S. security policy began to dissolve during the 1990s, after the demise of the Soviet Union. Further, in response to emerging threats to U.S. national security, the Bush Administration argued that the United States must alter its deterrence strategy "from 'one size fits all' deterrence to tailored deterrence for rogue powers, terrorist networks, and near-peer competitors."
During the Cold War, the United States often modified, or tailored, its nuclear targeting doctrine, its nuclear weapons employment policy, and its nuclear force structure to enhance or maintain the credibility of its nuclear deterrent posture. In some ways, the Bush Administration's concept of tailored deterrence follows the same pattern, using assessments of an adversary's society and values to identify a range of targets that might be threatened, and adjusting U.S. war plans and force structure to enhance the credibility of U.S. threats to destroy these targets. However, tailored deterrence differs from Cold War deterrence in that it explicitly notes that U.S. nuclear weapons could be used in attacks against a number of nations that might have developed and deployed chemical and biological weapons, even if they did not possess nuclear weapons. Hence, the new policy seems more of a change in "who" we will deter than it is a change in "how" we will deter.
Congress may review the concept of tailored deterrence, either as a part of its oversight of nuclear weapons policies and programs, or as a part of a broader debate about the role of nuclear weapons in U.S. national security policy. Issues that might come up in such a review are questions about how much U.S. nuclear strategy and weapons employment policy have changed in recent years; questions about whether the new capabilities and war plans will enhance the credibility of U.S. deterrent threats, or, conversely, make the use of nuclear weapons more likely; questions about whether the United States must develop new weapons capabilities to meet the demands of tailored deterrence, or whether it must retain a force structure with thousands of deployed warheads if it no longer uses "the Russian threat" as the metric for sizing the U.S. force; and questions about whether the new concepts and war plans expand or restrict the role of nuclear weapons in U.S. national security strategy.
The Obama Administration is also likely to review and revise this concept as it conducts its nuclear posture review. It may revise the rationale for why the United States retains nuclear weapons, in accordance with the President's pledge to reduce the role of nuclear weapons in U.S. national security strategy. It may also address questions about U.S. declaratory policy, and the role that other policy options may play in efforts to deter or defend against the proliferation of nuclear weapons and other weapons of mass destruction.
This report will not be updated again; it will be replaced by a new report on U.S. nuclear doctrine after the Obama Administration completes, and reports on, its nuclear posture review.