Can you think of anything that might have changed from 1945 to 1981 in terms of geopolitics, such that the use of nuclear weapons by the United States might have led to some sort of global thermonuclear war? In other words- and, excuse me, I'm not very familiar with the history here- was there some other nuclear "superpower" that was around during the 1980s which could, quite easily, destroy all major American population centers, and by all indications would if the U.S. used nuclear weapons against it? And did this other superpower develop its nuclear capability before 1945, or after 1945?
And might there have been some difference in the power of nuclear weapons between Fat Man/Little Boy and those deployed in the early 1980s? That could also make a difference, here.
Any insight here would be greatly appreciated- otherwise it sounds like a really dumb idea to discourage using nuclear weapons against Russia in the 1980s, and I don't know why anybody might want to make that harder.