SALT I and the ABM Treaty (1972): First Strategic Arms Limits

SALT I was the first agreement between the United States and the Soviet Union to limit their strategic nuclear weapons. Signed in Moscow on 26 May 1972 by Richard Nixon and Leonid Brezhnev, it consisted of the Anti-Ballistic Missile (ABM) Treaty and a five-year Interim Agreement that froze the number of long-range missile launchers. Although it did not reduce arsenals, it marked the high point of détente and set the framework for decades of arms control.

Background: the arms race and MAD

By the late 1960s both superpowers had thousands of nuclear warheads and the means to deliver them across continents. The Cuban Missile Crisis of 1962 had shown how close they could come to war, and the 1963 test ban treaty and the Nuclear Non-Proliferation Treaty of 1968 had shown that limited agreements were possible.

Strategic thinking rested on deterrence, often called mutual assured destruction (MAD): each side could absorb a first strike and still destroy the other. Two new technologies threatened that balance. Anti-ballistic missile systems might let one side shield itself, and multiple independently targetable re-entry vehicles (MIRVs) allowed one missile to carry several warheads aimed at different targets.

US Defense Secretary Robert McNamara pressed Soviet Premier Alexei Kosygin on missile defences at the Glassboro summit in New Jersey in June 1967. Talks were due to start in 1968, but the Soviet-led invasion of Czechoslovakia in August that year delayed them.

The negotiations

The Strategic Arms Limitation Talks opened in Helsinki on 17 November 1969 and then alternated between Helsinki and Vienna. The US delegation was led by Gerard C. Smith, director of the Arms Control and Disarmament Agency; the Soviet delegation by Deputy Foreign Minister Vladimir Semyonov.

Progress was slow. The two sides disagreed over what counted as a “strategic” weapon, whether to link limits on defences and offensive arms, and how to verify any deal. The Soviets wanted to restrict American missile defences, while Washington wanted to cap the fast-growing Soviet force of heavy intercontinental ballistic missiles (ICBMs).

The breakthrough came through a secret “back channel” between Henry Kissinger and the Soviet ambassador in Washington, Anatoly Dobrynin. On 20 May 1971 both governments announced that they would negotiate an ABM agreement together with certain limits on offensive weapons. Nixon’s opening to China in February 1972 added to Moscow’s interest in a deal.

The Moscow summit

The summit nearly collapsed before it began. In May 1972, in response to North Vietnam’s Easter Offensive, Nixon ordered the mining of Haiphong harbour, where Soviet ships unloaded supplies. The Soviet leadership decided to go ahead anyway.

Nixon became the first US president to visit Moscow, staying from 22 to 29 May 1972 before travelling on to Kiev. Final points were settled in late-night sessions, and on 26 May Nixon and Brezhnev signed the two agreements in St Vladimir’s Hall of the Grand Kremlin Palace. On 29 May they also signed the Basic Principles of Relations, a statement of intent to avoid confrontation.

What the agreements said

The ABM Treaty limited each country to two ABM deployment areas: one protecting its capital and one protecting an ICBM field. Each area could have no more than 100 interceptor missiles and launchers. Nationwide defences, and sea-, air-, space-based or mobile land-based ABM systems, were banned. The treaty was of unlimited duration. A 1974 protocol reduced the limit to one site each: the Soviet Union kept its system around Moscow, and the United States chose its missile field near Grand Forks, North Dakota.

The Interim Agreement froze the number of fixed land-based ICBM launchers at the level operational or under construction on 1 July 1972, for five years. It also capped submarine-launched ballistic missiles (SLBMs): up to 710 launchers on 44 submarines for the United States and up to 950 on 62 submarines for the Soviet Union, with older ICBMs to be scrapped to reach those ceilings.

Both agreements relied on “national technical means of verification”, chiefly satellites, and each side promised not to interfere with them. A Standing Consultative Commission was set up to handle compliance questions.

By the numbers

Key people

• Richard Nixon (1913–1994), US president, who made arms control with Moscow part of a wider strategy of détente alongside his opening to China.
• Leonid Brezhnev (1906–1982), general secretary of the Soviet Communist Party, who saw the agreements as recognition of Soviet strategic equality with the United States.
• Henry Kissinger (1923–2023), Nixon’s national security adviser, who negotiated the key compromises through his back channel with Ambassador Anatoly Dobrynin.
• Gerard C. Smith (1914–1994), head of the US delegation at the formal talks, who was often bypassed by the back channel and later described the experience in his memoir Doubletalk.
• Vladimir Semyonov (1911–1992), Soviet deputy foreign minister and chief negotiator throughout the talks.

The formal delegations, made up of diplomats, military officers and scientists, spent more than two years working through the technical details that made the final agreements possible. Their sessions in Helsinki and Vienna also built personal contacts between Soviet and American specialists that proved valuable in later negotiations.

Ratification and criticism

The US Senate approved the ABM Treaty by 88 votes to 2 on 3 August 1972. Congress approved the Interim Agreement by joint resolution in September, with an amendment by Senator Henry Jackson calling for equal numbers in any future treaty. Both agreements entered into force on 3 October 1972.

Critics argued that the Soviet Union had been allowed more launchers. Supporters answered that the United States had a lead in bombers and in MIRV technology, so the overall balance was roughly equal. Because MIRVs were not restricted, both sides went on to multiply their warhead numbers during the 1970s.

Legacy

SALT I was followed by talks on a permanent treaty. SALT II was signed in Vienna by Jimmy Carter and Brezhnev on 18 June 1979, but the US Senate never ratified it after the Soviet invasion of Afghanistan in December 1979. Later agreements, including the START I Treaty of 1991, went further and actually cut arsenals.

The ABM Treaty remained a cornerstone of arms control for three decades. In December 2001 the United States gave notice of withdrawal so that it could build missile defences, and the treaty ceased to bind it on 13 June 2002. SALT I also helped pave the way to the Helsinki Accords of 1975, the other great achievement of détente in Europe.

Timeline

• 1967, June: Lyndon Johnson and Alexei Kosygin discuss missile defences at Glassboro.
• 1969, 17 November: The Strategic Arms Limitation Talks open in Helsinki.
• 1971, 20 May: Washington and Moscow announce a framework for an ABM deal and offensive limits.
• 1972, 22 May: Nixon arrives in Moscow for the summit.
• 1972, 26 May: Nixon and Brezhnev sign the ABM Treaty and the Interim Agreement.
• 1972, 3 August: The US Senate approves the ABM Treaty by 88 votes to 2.
• 1972, 3 October: Both agreements enter into force.
• 2002, 13 June: US withdrawal from the ABM Treaty takes effect.

Why it matters

SALT I was the first time the superpowers agreed to put limits on the weapons that could destroy them both. It did not end the arms race, but it showed that rivals could negotiate verifiable limits, and it created habits and institutions on which later reductions were built.