In this event, the Soviet Union wanted to gain polititcal influence over Afghanistan and it's neighbouring areas by preventing other religious or polititcal factions from over throwing the communist government. Using nuclear weapons in this invasion would not have worked to the Soviet's advantage in garnering support from the Afghans, hence, it was not likely to have been used by them. Countries in support of the rebels in Afghanistan mostly aided through financial help, and non-nuclear weapons and public condemnation of Soviet actions.
