Anti - Ballistic Missile Treaty The Anti - Ballistic Missile Treaty ( ABM Treaty or ABMT ) was a treaty between the United States and the Soviet Union on the limitation of the anti - ballistic missile ( ABM ) systems used in defending areas against missile - delivered nuclear weapon s . Under the terms of the treaty , each party was limited to two ABM complexes , each of which were to be limited to 100 anti - ballistic missiles . Signed in 1972 , it was in force for the next 30 years until the US unilaterally withdrew from it in June 2002 . Background . Throughout the late 1950s and into the 1960s , the United States and the Soviet Union had been developing a series of missile systems with the ability to shoot down incoming ICBM warheads . During this period the US considered the defense of the US as a 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 NORAD ) . By the early 1960s , 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 a " real " ABM system . Work started on a short - range , high - speed counterpart known as the 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 . However , due to political debate , Sentinel never expanded beyond defense of missile - bases . An intense debate broke out in public over the merits of such a system . A number of serious concerns about the technical abilities of the system came to light , many of which reached popular magazines such as " Scientific American " . This was based on lack of intelligence information and reflected the American nuclear warfare theory and military doctrines . The Soviet doctrine called for development of their 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 . As this debate continued , a new development in ICBM technology essentially rendered the points moot . This was the deployment of the Multiple Independently targetable Reentry Vehicle ( MIRV ) system , allowing a single ICBM to deliver as many as ten separate warheads at a time . This way , any ABM defense system could be overwhelmed with the sheer numbers 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 electronic countermeasures and heavy decoys . R - 36M heavy missiles were carrying as many as 40 of them . These decoys would appear as warheads to ABM , effectively requiring engagement of 50 times more targets than before and rendering defense even less effective . At about the same time , the USSR reached strategic parity with the US in terms of ICBM forces . A nuclear war would no longer be a favorable exchange for the US , as both countries would be devastated . This led in the West to the concept of mutually assured destruction , MAD , in which any changes to the strategic balance had to be carefully weighed . To the U . S . , ABMs now seemed far too risky — it was better to have no defense than one that might trigger a war . ABM Treaty . As relations between the US and USSR warmed in the later years of the 1960s , the US first proposed an ABM treaty in 1967 . This proposal was rejected . 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 ( Art . III ) . The treaty was signed during the 1972 Moscow Summit on May 26 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 August 3 , 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 . It was seen by many in the West as a key piece in nuclear arms control , being an implicit recognition of the need to " protect " the nuclear balance by ensuring neither side could hope to reduce the effects of retaliation to acceptable levels . In the East , however , it was seen as a way to avoid having to maintain an anti - missile technology race at the same time as maintaining a missile race . For many years the ABM Treaty was , in the West , considered one of the landmarks in arms limitations . It was perceived as requiring two enemies to agree not to deploy a potentially useful weapon , deliberately to maintain the balance of power and as such , was also taken as confirmation of the Soviet adherence to the MAD doctrine . Missiles limited by the treaty . The Treaty limited only ABMs capable of defending against " strategic ballistic missiles " , without attempting to define " strategic " . It was understood that both ICBMs and SLBM s are obviously " strategic " . Both countries did not intend 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 . After the SDI announcement . The treaty was undisturbed until Ronald Reagan announced his Strategic Defense Initiative ( SDI ) on March 23 , 1983 . On the one hand , Reagan stated that SDI was " consistent with . . . the ABM Treaty " , but on the other hand , he viewed it as a defensive system that would help reduce the possibility that mutual assured destruction ( MAD ) would become reality ; he even suggested that the Soviets would be given access to the SDI technology . Nevertheless , SDI was against the spirit — if not the letter — of the ABM Treaty , which sought to pursue the principle of MAD . The project was a blow to Yuri Andropov ' s so - called " peace offensive " . Andropov said that " It is time they [ Washington ] stopped . . . search [ ing ] for the best ways of unleashing nuclear war . . . Engaging in this is not just irresponsible . It is insane " . SDI research went ahead , although it did not achieve the hoped - for result . SDI research was cut back following the end of Reagan ' s presidency , and in 1995 it was reiterated in a presidential joint statement that " missile defense systems may be deployed . . . [ that ] will not pose a realistic threat to the strategic nuclear force of the other side and will not be tested to . . . [ create ] that capability . " This was reaffirmed in 1997 . Regardless of the opposition , Reagan gave every indication that SDI would not be used as a bargaining chip and that the United States would do all in its power to build the system . The Soviets were threatened because the Americans might have been able to make a nuclear first strike possible . In " The Nuclear Predicament , " Beckman claims that one of the central goals of Soviet diplomacy was to terminate SDI . A surprise attack from the Americans would destroy much of the Soviet ICBM fleet , allowing SDI to defeat a “ ragged ” Soviet retaliatory response . Furthermore , if the Soviets chose to enter this new arms race , they would further cripple their economy . The Soviets could not afford to ignore Reagan ’ s new endeavor , therefore their policy at the time was to enter negotiations with the Americans . By 1987 , however , the USSR withdrew its opposition , concluding the SDI posed no threat . US withdrawal . After the dissolution of the Soviet Union in December 1991 the status of the treaty became unclear , debated by members of Congress and professors of law . In 1997 , a memorandum of understanding between the US and four of the former USSR states was signed and subject to ratification by each signatory , but it was not presented to the US Senate for advice and consent by Bill Clinton . On December 13 , 2001 , George W . Bush gave Russia notice of the United States ' withdrawal from the treaty , in accordance with the clause that required six months ' notice before terminating the pact — the first time in recent history that the United States has withdrawn from a major international arms treaty . This led to the eventual creation of the American Missile Defense Agency . Supporters of the withdrawal argued that it was a necessity in order to test and build a limited National Missile Defense to protect the United States from nuclear blackmail by a rogue state . The withdrawal had many critics as well as supporters . John Rhinelander , a negotiator of the ABM treaty , predicted that the withdrawal would be a " fatal blow " to the Nuclear Non - Proliferation Treaty and would lead to a " world without effective legal constraints on nuclear proliferation . " The construction of a missile defense system was also feared to enable the US to attack with a nuclear first strike . Reaction to the withdrawal by both the Russian Federation and the People ' s Republic of China was much milder than many had predicted , following months of discussion with both Russia and China aimed at convincing both that development of a National Missile Defense was not directed at them . In the case of Russia , the United States stated that it intended to discuss a bilateral reduction in the numbers of nuclear warheads , which would allow Russia to reduce its spending on missiles without decrease of comparative strength . Discussions led to the signing of the Strategic Offensive Reductions Treaty in Moscow on May 24 , 2002 . This treaty mandates cuts in deployed strategic nuclear warheads , but without actually mandating cuts to total stockpiled warheads , and without any mechanism for enforcement . References . Anti - Ballistic Missile Treaty 1974 Protocol