SALT II was never ratified by the U.S. Senate and therefore never entered into force. The treaty was signed in Vienna on June 18, 1979, and had strong support from both militaries, the arms control community, and a bipartisan majority of foreign policy specialists — but the Soviet invasion of Afghanistan on December 24, 1979 killed its prospects, and President Carter formally withdrew it from Senate consideration on January 3, 1980. Both the U.S. and the USSR continued to observe the treaty’s central numerical limits on a voluntary basis for years afterward.
The question of ratification collapsed on a single geopolitical event. See the SALT treaties and arms control for the full negotiation history.
When Carter submitted SALT II to the Senate in late June 1979, the agreement had strong support from both militaries, the arms control community, and a bipartisan majority of foreign policy specialists. The Senate Foreign Relations Committee held extensive hearings in July, August, and September 1979. The principal objections came from conservative Republicans, who argued that the treaty locked in Soviet advantages in heavy ICBMs and throw-weight. Senator Barry Goldwater, the ranking Republican on the Armed Services Committee, was a prominent opponent.
The Soviet invasion of Afghanistan, which began on December 24, 1979, killed SALT II’s prospects. The Carter administration imposed a grain embargo, a high-technology export ban, an Olympic boycott, and an increase in defense spending. On January 3, 1980, Carter asked the Senate to delay consideration of the treaty. SALT II was not formally killed, but it was suspended.
Both the U.S. and the USSR continued to observe the central numerical limits of SALT II for several years, even after the treaty was withdrawn. By 1986, the U.S. was no longer in compliance with the spirit of the SALT II limits, though not with its letter. The voluntary compliance demonstrated that the treaty’s terms were technically workable and that the verification regime could function in the absence of legal force. The data exchanges and the Standing Consultative Commission continued, framework built for SALT II became the technical basis for START I in 1991 — the Cold War’s most consequential arms control treaty, built on a treaty that was never legally in force.