In deploying NMD, the challenge facing the US is to devise a package of incentives that will secure Russian agreement to amend the ABM Treaty. The most promising would involve US concessions in a future START III Treaty to accommodate Moscow's interests. In particular, the US could allow Russia to deploy multiple independently targetable re-entry vehicles (MIRVs) on mobile intercontinental ballistic missiles (ICBMs), which are far less destabilising to the nuclear balance than many arms-control advocates assume. In addition, before making a deployment decision, the US should give greater attention to several 'boost-phase' NMD concepts which could produce a more effective defence with fewer negative consequences for relations between the major powers.

This paper examines how well future U.S. national and theater missile defense systems will have to perform to meet reasonable defense objectives as a function of the level of the threat. Deploying a thin U.S. national missile defense today is premature because the threat is not readily apparent, the United States can deter most threats, and the United States has some conventional counterforce options against a developing state's nascent ICBM arsenal.

However, if, or when, intercontinental ballistic missile threats appear, a defense with 100 interceptors deployed at one or two sites around the continental United States should be able to to intercept between 10 and 20 apparent warheads, assuming NMD systems can detect and track warheads with a probabilty above 0.99 and that NMD interceptors have a single-shot probability of kill (SSPK) against warheads between 0.35-0.65. Theater-range ballistic missiles present a greater near-term threat. The current THAAD program may provide an effective upper-tier defense, but only if it can achieve detection and tracking probabilities in the range 0.96-0.98 and interceptor SSPKs in the range 0.4-0.65 for threats with between 100-200 apparent warheads. Larger threats will require even higher technical performance.

Similarly, the current NTW program will require the same detection and tracking probability, but with interceptor SSPKs in the range of 0.55-0.80 to deal with the size of the threat.

Moreover, for these defenses to be truly useful, they must be accompanied by an equally effective lower tier, e.g., using PAC-3 terminal defenses. The main challenge for upper- and lower-tier defenses is responsive threats that use countermeasures such as decoys and chemical or biological submunitions. Airborne boost-phase theater missile defenses are relatively robust with respect to these countermeasures and they pose relatively little threat to the nuclear forces of the five major nuclear powers. Hence, more emphasis should be placed on such systems in current U.S. missile defense plans.

This paper develops a probabilistic model that can be used to determine the number of ballistic missile defense interceptors required to meet a specific defense objective, given the technical performance of the defense. The defense objective is stated as some probability that no warheads leak through the defense. The defense technical performance is captured by the interceptor single-shot probability of kill and the warhead detection, tracking, and classification probability. Attacks are characterized by the number of warheads and decoys that cannot be discriminated by the defense. Barrage and shoot-look-shoot firing modes are examined, with the optimal interceptor allocation derived for the shoot-look-shoot mode. Applications of this model to national and theater missile ballistic missile defense are discussed.

The majority of Russia's current strategic nuclear force will become obsolete shortly after the turn of the century. Hence, Russian strategic force modernization is essential if Russia is to remain a nuclear power on a par with the United States. Numerous uncertainties, especially financial uncertainties, prevent accurate estimates of Russia's future strategic force structure. Nevertheless, under the START I Treaty, Russia can probably maintain a force with slightly more than 4,000 strategic nuclear warheads over the next two decades-about half the number of the United States. Under START II, Russia is likely to maintain a strategic force of between 1,800 and 2,500 warheads, compared to 3,500 warheads for the United States. Therefore, Russia's main interest in ratifying the START II Treaty would be to pursue a START III Treaty that limits both sides to between 2,000 and 2,500 strategic nuclear warheads. This is the least expensive way to retain rough parity with the United States. Several reasons have been educed for why Russia should not ratify the START II Treaty, namely, because the Treaty allows a U.S. advantage in reconstitution capability and prompt hard-target-kill capability. However, these advantages are neither so great nor so consequential that Russia should reject the START II Treaty for these reasons alone. If Russia ratifies the START II Treaty, and presumably a follow-on START III Treaty, Russia's future strategic nuclear force will appear a lot different than its Soviet predecessor due to the reduced emphasis on land-based ICBMs. Nevertheless, the Russian force should remain a highly survivable, stable force-assuming Russian leaders allocate sufficient resources to ensure that their ballistic missile submarines, mobile ICBMs, and bombers can survive all plausible counterforce threats.

Future regional conflicts will almost certainly involve politically less stable nations or other regional actors using theater ballistic missiles armed with either nuclear, biological, or chemical warheads. The United States Air Force is attempting to deal with this threat by developing the Airborne Laser (ABL) with the goal of shooting down missiles while they are still under power and before they can release submunitions possibly containing highly toxic biological agents. This paper presents the results of an analysis of this system. It is based solely on information found in the open literature and using the basic physics and engineering involved in transmitting intense laser beams through the atmosphere. The ABL's potential capabilities and possible theaters of operation are discussed at a non-technical level.

The renewed American debate over ballistic missile defenses (BMD) echoes loudly in NATO, in Europe, and in France. This issue will be decisive for the future of European political organization and its security and defense. The issue will also be important for the future of relations between Europe, the United States, and Russia.

Faced with the potential threat of ballistic missiles equipped with nuclear warheads (or biological and chemical payloads) that could strike French and European territories, deterrence is sufficient and offers the greatest cost-effectiveness. In this analysis, the question of the broadening of the French and British deterrent and the political organization of a possible European anti-missile defense system will be discussed. Then, a new transatlantic strategic partnership, the robustness of which lies in counterbalancing the vulnerabilities of its members, will be described.

This volume contains the proceedings of a conference held at the Center for International Security and Arms Control in May 1996. The meeting was the latest in a series that CISAC had held over the years with Russian specialists from the Center for Scientific Research of the Committee of Scientists for Global Security, the Ministry of Defense, and the Russian Academy of Sciences. The general rubric under which these meetings were organized is "Strategic Stability to the Year 2000."

The May meeting had a special significance because 1996 was a year of presidential elections in both Russia and the United States, and the prospect of these elections was inevitably reflected in the discussions. But another general point emerged in the meeting, and that was the need to pay more attention to the strategic relationship between Russia and the U.S. Much had been done since the end of the Cold War to wind down the nuclear competition between the two countries, and agreements have been signed to reduce the enormous nuclear arsenals built up during the Cold War. There is much to be done, however, to ensure that this course is continued. The uncertainty
about ratification of START II by the State Duma, and the proposals in the U.S. Congress for deployment of a national ABM system both cast doubt on the possibility of further reductions in strategic offensive arms. The prospects for pushing nuclear weapons into the background of international politics are clouded by the renewed Russian interest in the role of tactical weapons in regional conflicts, and by U.S. interest
in the use of nuclear weapons to deter chemical and biological weapons attacks.

The issues discussed in the conference are embedded in broader political relationships, and this meeting suggested the need for a more intensive and broader strategic dialogue. In both countries there had been a lessening of interest in issues of arms control, but the process of reducing and eliminating nuclear weapons, to which both states are formally committed, is a complex and contentious one, which requires
political trust and careful management. Hence, the importance of a strategic dialogue which examines the conceptual basis of Russian-U.S. relations. Several participants in the conference spoke of the need to transform, or move away from, nuclear deterrence.
Many proposals were advanced for further cooperation in arms control and disarmament. But it is clear that much remains to be done to move Russian-U.S. relations onto a more stable footing.