At the time the talks began, the Soviets held a slight advantage in ABM technology; the United States, however, was quickly moving ahead in developing MIRVs, which would give it a tremendous qualitative advantage over Soviet offensive missile systems. From the U.S. perspective, control of ABMs was key. After all, no matter how many missiles the United States developed, if the Soviets could shoot them down before they struck their targets they were of limited use. And, since the Soviets had a quantitative lead in the number of intercontinental ballistic missiles (ICBMs) and submarine launched ballistic missiles (SLBMs), an effective Soviet ABM system meant that the Russians could launch devastating nuclear attacks with little fear of reprisal.
From the Soviet side, the U.S. development of MIRV technology was particularly frightening. Not only were MIRV missiles technologically superior to Soviet weapons, there were also questions as to whether even an advanced ABM system could protect the Soviet Union from this type of missile. It was obviously time to discuss what seemed to be a never-ending arms race.
The SALT I agreement reached in May 1972 limited each nation to no more than 100 ABM launchers at each of two sites of their own choosing. Offensive weapons were also limited. The United States would be held to 1,000 ICBMs and 710 SLBMs; the Soviets could have 1,409 ICBMs and 950 SLBMs. The administration of President Richard Nixon defended the apparent disparity by noting that nothing had been agreed to concerning MIRVs. American missiles, though fewer in number, could therefore carry more warheads.
Whether all of this made the world much safer was hard to say. The United States and Soviet Union essentially said they would limit efforts to both defend themselves and destroy the other. Their nuclear arsenals, however, were still sufficient to destroy the world many times over.