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Soviet–U.S. relations

During his eighteen years as Leader of the USSR, Brezhnev's signature foreign policy innovation was the promotion of détente. While sharing some similarities with approaches pursued during the Khrushchev Thaw, Brezhnev's policy significantly differed from Khrushchev's precedent in two ways. The first was that it was more comprehensive and wide-ranging in its aims, and included signing agreements on arms control, crisis prevention, East–West trade, European security and human rights. The second part of the policy was based on the importance of equalizing the military strength of the United States and the Soviet Union. Defense spending under Brezhnev between 1965 and 1970 increased by 40%, and annual increases continued thereafter. In the year of Brezhnev's death in 1982, 12% of GNP was spent on the military. Under Brezhnev the Soviet Union's military budget increased eightfold, resulting in the possession of the largest number of ICBMs, nuclear warheads, aircraft, tanks, conventional forces and more military assets. This build up led numerous observers – including Western ones – to argue that by the mid-1970s the USSR had surpassed the United States as the world's strongest military power.

At the 1972 Moscow Summit, Brezhnev and U.S. President Richard Nixon signed the SALT I Treaty. The first part of the agreement set limits on each side's development of nuclear missiles. The second part of the agreement, the Anti-Ballistic Missile Treaty, banned both countries from designing systems to intercept incoming missiles so neither the U.S. or the Soviet Union would be emboldened to strike the other without fear of nuclear retaliation.

By the mid-1970s, Henry Kissinger 's policy of détente towards the Soviet Union was faltering. The détente had rested on the assumption that a "linkage" of some type could be found between the two countries, with the U.S. hoping that the signing of SALT I and an increase in Soviet–U.S. trade would stop the aggressive growth of communism in the third world. This did not happen, as evidenced by Brezhnev's continued military support for the communist guerillas fighting against the U.S. during the Vietnam War.

After Gerald Ford lost the presidential election to Jimmy Carter, American foreign policies became more overtly aggressive in vocabulary towards the Soviet Union and the communist world. Attempts were also made to stop funding for repressive anti-communist governments and organizations the United States supported. While at first standing for a decrease in all defense initiatives, the later years of Carter's presidency would increase spending on the U.S. military. When Brezhnev authorized the Soviet invasion of Afghanistan in 1979, Carter, following the advice of his National Security Adviser Zbigniew Brzezinski, denounced the intervention, describing it as the "most serious danger to peace since 1945". The U.S. stopped all grain exports to the Soviet Union and boycotted the 1980 Summer Olympics held in Moscow. The Soviet Union responded by boycotting the 1984 Summer Olympics held in Los Angeles.

During Brezhnev's rule, the Soviet Union reached the peak of its political and strategic power in relation to the United States. As a result of the limits agreed to by both superpowers in the first SALT Treaty, the Soviet Union obtained parity in nuclear weapons with the United States for the first time in the Cold War. Additionally, as a result of negotiations during the Helsinki Accords, Brezhnev succeeded in securing the legitimization of Soviet hegemony over Central and Eastern Europe.