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26 May 1972Reputable sourceWell documented

The superpowers agree, for the first time, to stop building more

On the timeline · around 26 May 1972 · DétenteDétenteThe superpowers agree, for the first time, to stop building more197019711972197319741975

What happened

After more than two years of negotiation begun in Helsinki, Nixon and Soviet leader Leonid Brezhnev signed the ABM Treaty and an interim SALT agreement in Moscow, the first time in the Cold War either superpower had agreed to limit the number of nuclear weapons in its arsenal rather than simply keep building. The ABM Treaty capped each side at 200 missile-defense interceptors across two sites, a deliberate choice to leave both countries vulnerable to attack, since a functioning missile shield might otherwise tempt one side to strike first without fear of retaliation. A planned second round, SALT II, dragged on through three US presidencies and was finally signed in 1979, only for the Senate to shelve it entirely after the Soviet invasion of Afghanistan that same December.

Why it matters

SALT I is considered the high-water mark of détente, the brief thaw in superpower relations built on the idea that mutual vulnerability, rather than missile defense, was what actually kept the peace, a logic that would come under direct challenge just over a decade later when Reagan proposed defending against missiles instead of merely deterring them.

How we know

The ABM Treaty and interim SALT agreement's texts, along with the specific interceptor and launcher limits they set, are matters of signed international record, letting historians verify the treaty's exact provisions rather than relying on summaries.

Sources

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