Russia has long been concerned with U.S. ballistic missile defense programs, arguing that the increasing capabilities of U.S. missile defenses could undermine Russia's strategic offensive nuclear forces and undermine strategic stability. During the Strategic Arms Limitation Talks (SALT) in the 1970s, the United States and Soviet Union had addressed the link between offensive and defensive systems in their arms control treaty negotiations. However, in recent years, the United States has argued that the ballistic missile defense (BMD) programs it is pursuing will be neither numerous enough nor capable enough to intercept Russia's strategic offensive ballistic missiles or undermine Russia's strategic nuclear deterrent. The United States and Russia signed the New START Treaty—the Treaty ... on Measures for the Further Reduction and Limitation of Strategic Offensive Arms—on April 8, 2010, and it awaits Senate consideration. New START is not of unlimited duration; it would expire 10 years after it enters into force. When President Obama and President Medvedev launched the negotiations on this treaty in April 2009, they agreed that the two nations would address Russia's concerns with U.S. missile defense programs in a separate forum from the negotiations on a New START Treaty. However, during their meeting in Moscow in July 2009, they agreed that the new treaty would contain a "provision on the interrelationship of strategic offensive arms and strategic defensive arms." This statement, which appears in the preamble to New START, states that the parties recognize the existence of the interrelationship between strategic offensive arms and strategic defensive arms, that this interrelationship will become more important as strategic nuclear arms are reduced, and that current strategic defensive arms do not undermine the viability and effectiveness of the strategic offensive arms of the parties. Russia and the United States each issued unilateral statements when they signed New START that clarified their positions on the relationship between New START and missile defenses. Russia stated that the Treaty can operate and be viable only if the United States of America refrains from developing its missile defense capabilities quantitatively or qualitatively. Consequently, the exceptional circumstances referred to in Article 14 of the Treaty include increasing the capabilities of the United States of America's missile defense system in such a way that threatens the potential of the strategic nuclear forces of the Russian Federation. In its statement, the United States stated that its missile defense systems are not intended to affect the strategic balance with Russia. The United States missile defense systems would be employed to defend the United States against limited missile launches, and to defend its deployed forces, allies and partners against regional threats. The United States intends to continue improving and deploying its missile defense systems in order to defend itself against limited attack and as part of our collaborative approach to strengthening stability in key regions. Russia's Foreign Minister, Sergei Lavrov, indicated, in a press conference after the negotiators completed the treaty, that the language in the Treaty preamble was set down in a "legally binding" form. He stated, further, that the sides had appropriate levels of strategic offensive arms at this point, but "if there are changes to these levels, each side reserves the right to make a decision on whether to continue to take part in the process of strategic offensive arms cuts." Some in the United States have questioned whether this statement means that the United States and Russia agreed that increases in U.S. ballistic missile defenses would upset stability, and therefore that they could serve as cause to terminate the New START Treaty. Moreover, they have expressed concerns that, if the United States has not accepted this interpretation, the two parties hold different interpretations of their obligations under the Treaty and that these differences could disrupt the treaty's implementation. The Obama Administration has agreed that the language in the treaty preamble is "legally binding," in that it is a part of the formal text of the Treaty. But the Administration has insisted that the preamble contains no legal or practical limits on missile defense and imposes no obligations on the United States. Moreover, the Administration has insisted, as Under Secretary of State Ellen Tauscher stated, "Russia's unilateral statement on missile defenses is not an integral part of the New START Treaty. It's not legally binding. It won't constrain U.S. missile defense programs." Nevertheless, some have questioned whether Russia's threat to withdraw from New START might have a "chilling effect" on U.S. missile defense plans and programs. They contend that the United States might limit these programs itself to avoid a possible disruption of the arms control process or the possible increase in tensions with Russia. As Senator Jeff Sessions noted in a speech on May 13, 2010, "I can't help but worry that these provisions will have a negative impact on U.S. decision-making with respect to missile defense." Members of the Senate are likely to raise this question, and explore the potentially different U.S. and Russian views on the relationship between New START and U.S. ballistic missile defense programs, during the debate on the New START Treaty. When the United States and Soviet Union negotiated the 1991 START Treaty, the Soviet Union also sought to link limits on offensive nuclear weapons with limits on ballistic missile defenses. The United States did not agree to the Soviet proposals, so the Soviet Union released a unilateral statement when it signed START, noting that the Treaty would not remain in force if the United States withdrew from the 1972 ABM Treaty. This statement did not serve to slow U.S. missile defense programs after START entered into force. Moreover, the United States and Soviet Union held discussions during the latter half of the 1990s on possible modifications to the ABM Treaty so that the United States could deploy more extensive ballistic missile defenses without withdrawing from the Treaty. These negotiations proved unsuccessful. Russia continued to object to U.S. ballistic missile defense plans and to caution the United States not to withdraw from the Treaty. Nevertheless, when the United States withdrew from the ABM Treaty in 2002, Russia did not withdraw from START. This report seeks to shed some light on the past relationship between ballistic missile defenses and negotiations on offensive arms control treaties. It provides aN historical review of the way in which the United States and Soviet Union addressed ballistic missile defense issues during their negotiations on the first Strategic Arms Reduction Treaty (START) in the 1980s and early 1990s. It also provides a review of U.S. missile defense policy and summarizes data on missile defense spending during the 1980s, 1990s, and the past decade. The report then reviews the recent record on the way the New START negotiations addressed ballistic missile defense issues and offers some observations about whether this historical record may provide insights into how the United States might proceed with its ballistic missile defense programs in the future. Russia's concerns about U.S. missile defense programs derive from its stated concern that missile defenses could upset strategic stability by undermining the effectiveness of Russia's offensive nuclear weapons. Specifically, Russia appears to be concerned that, if the United States were to increase the numbers and capabilities of its missile defense interceptors while Russia was reducing its numbers of deployed offensive weapons, the time may come when the United States believed it had the ability to launch a first strike against Russia's strategic forces while protecting itself from Russia's retaliatory attack with its missile defenses. In this environment, Russia may believe it had to increase its offensive forces so that it would have enough surviving weapons to penetrate the U.S. missile defenses. Such a response could require a withdrawal from the New START Treaty. Many analysts argue that this "Cold War" view of the relationship between U.S. missile defenses and Russian offensive weapons should not be relevant in the current strategic environment, in which the United States and Russia are not poised on the brink of conflict. The Bush Administration emphasized this point when it noted, in the 2001 Nuclear Posture Review, that the United States would "no longer plan, size or sustain its nuclear forces as though Russia presented merely a smaller version of the threat posed by the former Soviet Union." This change in the U.S.-Russian relationship was also evident in U.S. ballistic missile defense plans that were intended to address concerns about emerging threats and adversaries. As a result, this Cold War offense-defense scenario is not consistent with the capabilities planned for U.S. missile defenses or the U.S. intent in deploying these systems. Specifically, the United States is pursuing missile defenses to defend its allies and forces overseas against threats from shorter and medium-range missiles that they might encounter in regional conflicts around the world, and to defend the continental United States from threats that might emerge as nations deploy small numbers of long-range ballistic missiles. Thus, although the United States may eventually be able to defend against a force of dozens of long-range missiles from an emerging adversary, it would not have the ability to defend against an attack with hundreds of Russian missiles. This model of strategic stability was, however, relevant to assessments of the relationship between offensive and defense weapons during the Cold War. It is seen to have had a significant effect on the way that arms control agreements negotiated in the 1970s and 1980s addressed missile defenses and offensive reductions. In theory, strategic stability refers to the condition that exists when two potential adversaries recognize that neither would gain an advantage if it were to begin a conflict with the other. Each party would recognize not only that the costs of the conflict, even if it launched the first strike, would outweigh the gains that might be realized, but also that the other side was likely to draw the same conclusion. Each would know that, even if it were attacked, enough of its forces could survive the first strike to retaliate against the other side with a devastating response. And each would know that, even if it did attack first, the other side would have enough forces surviving the strike to launch a devastating retaliatory attack. Hence, neither would feel compelled to shoot first, because the costs of doing so would far outweigh the benefits. This situation, where each side is equally vulnerable to retaliation from the other, is considered to be stable. This model of strategic stability postulates a strong relationship between offensive forces and defensive forces.