What did the United States and the Soviet Union agree to do under the terms of the Strategic Arms Limitation Treaty (SALT) ?

They agreed to stop making nuclear ballistic missiles and to reduce the number of anti-ballistic missiles in their arsenals ... However, did not reduce weapons such as MIRV's which were much more sophisticated weapons.

Explanation:

In 1972, the United States and Soviet Union signed the Strategic Arms Limitation Treaty (SALT). They agreed to stop making nuclear ballistic missiles and to reduce the number of anti-ballistic missiles in their arsenals ... However, did not reduce weapons such as MIRV's which were much more sophisticated weapons.