Since 1972 the Anti-Ballistic Missile (ABM) Treaty has been one of the fundamental building blocks of U.S.-Soviet and U.S.-Russian arms control efforts. By severely restricting the deployment of defensive systems that could undermine deterrent capabilities, the ABM Treaty removed a potential incentive to increase strategic nuclear forces and allowed substantial force reductions to be negotiated in the START I and II agreements. Although the Cold War has ended, the treaty may still have important roles today and in the future. In particular, future deep reductions in U.S. and Russian strategic forces, as well as in the nuclear forces of other countries, may be impossible without the assurances granted by the treaty.
The Clinton administration recently proposed to Russia that the ABM Treaty be modified and that new agreed definitions be adopted to "clarify" how to interpret the treaty. The administration's stated objective is to allow the United States and Russia to develop and deploy anti-tactical ballistic missile (ATBM) defenses capable of engaging theater ballistic missiles (TBMs) with ranges up to 3,500 kilometers. Warheads delivered by missiles of this range would reenter the atmosphere at a speed of 5 kilometers per second, compared to roughly 7 kilometers per second for warheads delivered by a strategic ballistic missile with a range of 10,000 kilometers.
Our analysis indicates that a highly capable ATBM system--one capable of protecting a large ground area against theater warheads reentering the atmosphere at up to 5 kilometers per second--would almost certainly have a significant capability against strategic warheads as well. These proposed changes to the treaty could therefore undermine the core of what the ABM Treaty was designed to prohibit.
Impact of the Gulf War
The Iraqi ballistic missile attacks on Israel and Saudi Arabia during the 1991 Gulf War increased concerns about the potential threat posed to U.S. troops and allies by TBMs. Although the Iraqi attacks were militarily ineffective and caused relatively few casualties, their psychological impact was enormous. Moreover, there is concern that additional countries are acquiring TBMs or weapons of mass destruction or may do so in the not too distant future. Consequently, the United States has shifted the focus of its missile defense program from countering strategic ballistic missiles to developing systems to counter TBMs.
The more advanced theater missile defense systems now being developed by the United States, such as the Theater High Altitude Area Defense (THAAD) system, would have capabilities so great that the ABM Treaty--as currently interpreted--would not allow their testing or deployment. To permit development and testing of such defenses to proceed, the administration has proposed that the treaty be modified to allow a missile defense system to be developed and deployed, provided it is not tested against a target with a peak reentry speed of greater than 5 kilometers per second.
The Clinton administration argues that the proposed changes are simply clarifications, and would not undermine the treaty's ability to limit defenses against strategic ballistic missiles. However, while administration officials and some independent analysts have asserted that these changes will preserve the original intent of the ABM Treaty while allowing highly capable ATBMs, they have presented no analysis to support this position.(1)
Our analysis demonstrates that the administration's assertion is wrong. Deployment of highly capable ATBM systems is the objective of the THAAD program and of U.S. ATBM programs more generally. Thus, the administration's proposals could well have the effect of eliminating the ABM Treaty as a practical mechanism for preventing the deployment of significant defenses against strategic missiles.
To understand the problems and issues posed by the proposed treaty changes, it is worthwhile to review the restrictions on testing and deployment of missile defenses contained in the ABM Treaty as it is currently written and interpreted, consider the effect of the changes proposed by the Clinton administration, and examine the operational and technical characteristics of missile defense systems that determine their defensive capabilities. …