Signed in 1972, it was in force for the next thirty years until the US unilaterally withdrew from it in 2002.
By the early 1960s, US research on the Nike Zeus missile system (see Project Nike) 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, which still remains the only operational ABM system 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 missile to deliver several warheads at a time. With this system the USSR could simply overwhelm the ABM defense system with numbers, as the same number of missiles could carry ten times more warheads. Upgrading it to counter the additional warheads would cost more than the handful of missiles needed to overwhelm the new system, as the defenders required one rocket per warhead, whereas the attackers could place 10 warheads on a missile with more affordable cost than development of ABM. To further protect against ABM systems, the Soviet MIRV missiles were equipped with electronic countermeasures and heavy decoys, with heavy missiles like R-36 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 ineffective.
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, but 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 US, ABMs now seemed far too risky – it was better to have no defense than one that might trigger a war.
In the East however, the concept of MAD was almost entirely unknown to the public, studied only by those in the Soviet military and Government who analyzed Western military behavior. Soviet military theory fully involved the mass use of nuclear devices, in combination with massive conventional forces.
The treaty was signed in Moscow on May 26 1972 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 Grand Forks Air Force Base, North Dakota, since its Safeguard facility was already under construction, for the US.
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. The US at this time was allocating about 5% of their GDP on military spending. The USSR was allocating about 40% of their GDP, due to smaller overall economic base.
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.
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 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.
The competitive pressure of SDI added considerable additional strains to the Soviet economy. The Soviet economy was essentially still a war economy after World War II, with increase of civilian production disproportionally small compared to growth of defense industry. It was already slowly becoming clear that the Soviet economy could not continue as it was, with military spending absorbing 40% of GDP; the additional demands from the military-industrial complex to compete with SDI exacerbated this problem and was part of the longer term situation which led to Gorbachev's efforts at economic reform (which failed, due to the need for initial political reform, which in turn led to his efforts to achieve political reform, which led to the fairly accidental collapse of the Party).
On December 13, 2001, George W. Bush gave Russia notice of the United States' withdrawal from the treaty, in accordance with the clause that requires six months notice before terminating the pact. This was the first time in recent history the United States has withdrawn from a major international arms treaty. This led to the eventual creation of the 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 mandated the deepest ever cuts in deployed strategic nuclear warheads, without actually mandating cuts to total stockpiled warheads.