The 1972 Strategic Arms Limitation Treaty I (Interim Agreement), among others, resulted from four years of dialogue between the United States and the Soviet Union known as the Strategic Arms Limitations Talks (SALT). The primary objective of both parties was to curb the rapid armament of offensive strategic ballistic missiles, both on land and at sea. The Interim Agreement froze each nation’s intercontinental ballistic missiles (ICBMs) and submarine-launched ballistic missiles (SLBMs) levels for five years, under the auspices of the forthcoming SALT II negotiations in Vienna which would mandate reductions on specific weapons and delivery systems.
The talks corresponded with an unstable buildup of strategic weapons on both sides. During the years leading up to the Interim Agreement, the Soviets had dramatically increased their supply of ICBMs and submarine-launched missiles, surpassing the United States for the first time in the number of land-based ICBMs. This asymmetry was a problem for the United States, as some American allies relied on these long-range weapons for their defense. Meanwhile, the United States focused its attention on equipping its missiles with multiple independent reentry vehicles (MIRV) which threatened the Soviets’ limited amount of anti-ballistic missile (ABM) systems.
President Richard Nixon and General Secretary Leonid Brezhnev signed the agreement on May 26, 1972 in Helsinki, Finland. Satellites using space-based imaging, rather than human physical presence, ensured verification and compliance. Importantly, each side agreed not to interfere with the other’s verification efforts.
The Interim Agreement set the stage for the first-ever reduction in the number of nuclear weapons in existence.