What was a significant reason the SALT II treaty was not ratified?

The significant reason the SALT II treaty was not ratified lies in the context of the geopolitical tensions that arose following the USSR's invasion of Afghanistan in 1979. This event sparked widespread concern in the United States about the Soviet Union's intentions and perceived aggression, leading to heightened fears of Soviet expansionism.

As a result of this invasion, many U.S. lawmakers and the public began to view the SALT II treaty, which aimed to limit the arms race between the two superpowers, as being inadequate in curtailing Soviet military ambitions. The environment of distrust that the invasion fostered made it politically unfeasible to support arms limitation when there was a belief that the USSR was not committed to peace or stability in the region.

Consequently, the combination of growing domestic opposition, fueled by fears linked to the Soviet actions in Afghanistan, resulted in the Senate ultimately choosing not to ratify the treaty, despite previous negotiations aimed at limiting nuclear arms. This reflected the broader, more immediate concerns of U.S. security and foreign policy at that time, overshadowing the long-term goals of disarmament that SALT II represented.