Anti-Ballistic Missile Treaty

The Anti-Ballistic Missile Treaty (ABM Treaty or ABMT) (1972—2002) was an arms control treaty between the United States and the Soviet Union on the limitation of the anti-ballistic missile (ABM) systems used in defending areas against ballistic missile-delivered nuclear weapons. Under the terms of the treaty, each party was limited to two ABM complexes, each of which was to be limited to 100 anti-ballistic missiles. The Anti-Ballistic Missile Treaty (ABM Treaty or ABMT) (1972—2002) was an arms control treaty between the United States and the Soviet Union on the limitation of the anti-ballistic missile (ABM) systems used in defending areas against ballistic missile-delivered nuclear weapons. Under the terms of the treaty, each party was limited to two ABM complexes, each of which was to be limited to 100 anti-ballistic missiles. Signed in 1972, it was in force for the next 30 years. In 1997, five years after the dissolution of the Soviet Union, four former Soviet republics agreed with the United States to succeed the USSR's role in the treaty. In June 2002 the United States withdrew from the treaty, leading to its termination. Throughout the late 1950s and into the 1960s, the United States and the Soviet Union had been developing missile systems with the ability to shoot down incoming ICBM warheads. During this period, the US considered the defense of the US as part of reducing the overall damage inflicted in a full nuclear exchange. As part of this defense, Canada and the US established the North American Air Defense Command (now called North American Aerospace Defense Command). By the early 1950s, US research on the Nike Zeus missile system had developed to the point where small improvements would allow it to be used as the basis of an operational ABM system. Work started on a short-range, high-speed counterpart known as Sprint to provide defense for the ABM sites themselves. By the mid-1960s, both systems showed enough promise to start development of base selection for a limited ABM system dubbed Sentinel. In 1967, the US announced that Sentinel itself would be scaled down to the smaller and less expensive Safeguard. Soviet doctrine called for development of its own ABM system and return to strategic parity with the US. This was achieved with the operational deployment of the A-35 ABM system and its successors, which remain operational to this day. The development of multiple independently targetable reentry vehicle (MIRV) systems allowed a single ICBM to deliver as many as ten separate warheads at a time. An ABM defense system could be overwhelmed with the sheer number of warheads. Upgrading it to counter the additional warheads would be economically unfeasible: The defenders required one rocket per incoming warhead, whereas the attackers could place 10 warheads on a single missile at a reasonable cost. To further protect against ABM systems, the Soviet MIRV missiles were equipped with decoys; R-36M heavy missiles carried as many as 40. These decoys would appear as warheads to an ABM, effectively requiring engagement of five times as many targets and rendering defense even less effective. The United States first proposed an anti-ballistic missile treaty at the 1967 Glassboro Summit Conference during discussions between U.S. Secretary of Defense Robert McNamara and Chairman of the Council of Ministers of the Soviet Union Alexei Kosygin. McNamara argued both that ballistic missile defense could provoke an arms race, and that it might provoke a first-strike against the nation fielding the defense. Kosygin rejected this reasoning. They were trying to minimize the number of nuclear missiles in the world. Following the proposal of the Sentinel and Safeguard decisions on American ABM systems, the Strategic Arms Limitation Talks began in November 1969 (SALT I). By 1972 an agreement had been reached to limit strategic defensive systems. Each country was allowed two sites at which it could base a defensive system, one for the capital and one for ICBM silos. The treaty was signed during the 1972 Moscow Summit on 26 May by the President of the United States, Richard Nixon and the General Secretary of the Communist Party of the Soviet Union, Leonid Brezhnev; and ratified by the US Senate on 3 August 1972. The 1974 Protocol reduced the number of sites to one per party, largely because neither country had developed a second site. The sites were Moscow for the USSR and the North Dakota Safeguard Complex for the US, which was already under construction. The Treaty limited only ABMs capable of defending against 'strategic ballistic missiles', without attempting to define 'strategic'. It was understood that both ICBMs and SLBMs are obviously 'strategic'. Neither country intended to stop the development of counter-tactical ABMs. The topic became disputable as soon as most potent counter-tactical ABMs started to be capable of shooting down SLBMs (SLBMs naturally tend to be much slower than ICBMs), nevertheless both sides continued counter-tactical ABM development.