Here's another panel discussion from
GenCon: The 75th Anniversary of the First Soviet Nuclear Test.
We are talking about a moment that changed everything. The US was able to gain a decisive win in World War II because of its monopoly on nuclear weapons -- and the Japanese didn't realize that the two we dropped on them were all we had in our arsenal, and it would take months to construct more.
However, by the Korean War that balance had shifted. Had the US still held a monopoly on nuclear weapons, Truman probably could've given MacArthur permission to nuke the troop concentrations in China across the Yalu River and that would've been the end of things. The Reds would've been given a sharp punch in the snout that might well have curbed their ambitions for several decades, perhaps even led to their fall decades earlier.
Instead, Truman had to consider the fact that the USSR had nuclear weapons too -- and there was no telling how many or how reliable. So he ended up sacking MacArthur, and the Korean War ended in a ceasefire and an uneasy not-peace that has held for three quarters of a century.
Some people have argued that the US should've gone ahead and acted decisively at that point, when the Soviet Union's status as a nuclear power was still in its infancy, instead of getting the West accustomed to not being allowed to actually win wars any more, just reach the point at which the other side was willing to have a ceasefire.
Alternate History grandmaster Harry Turtledove's trilogy The Hot War, composed of
Bombs Away,
Fallout, and
Armistice, explores a war in which Truman approved the use of a limited number of nukes against troop concentrations in the People's Republic of China, and Stalin responded with nuclear attacks of his own. By the middle volume it has become tit-for-tat attacks on civilian population centers, as well as a conventional invasion of West Germany with a fair amount of personal ugliness as still-raw memories of Nazi atrocities are acted out on civilians.
It's clearly based upon the image of strength the Soviet Union projected during the Cold War -- unsurprising given that Harry Turtledove's formative years were spent in that period, when we really believed that the arms race was neck and neck, and we were in real danger of being overwhelmed.
In retrospect, with information that came out between the 1991 dissolution of the Soviet Union and Putin's clamping down on access to Soviet archives in the early 2000's, it's likely that Turtledove is basing his work on sources that overestimated both the Soviet Union's stockpile of nuclear weapons at that time and the reliability of those weapons. We know now that much of the appearance of Soviet military might was a maskirovka in the tradition of the Potemkin Villages of Catherine the Great's inspection of the Crimea. New tanks, planes and missiles were sent past the reviewing stand two, three and four times to create the illusion that the May Day, Victory Day and October Revolution parades were full of enormous numbers of high-tech armaments -- and that they were but a representative sample, not the entirety of what the USSR had available.
Not to mention that the mere fact that weapons systems were being paraded was no guarantee that they would actually work in times of war. It is now known that most of those armaments were made by slave labor in prison camps and other corrective facilities. This was particularly true of nuclear weapons, where it was considered more cost-effective to put them together with disposable prison labor than to put in adequate shielding for skilled laborers -- with the expected consequences on reliability. Maintenance also tended to be haphazard, even when supplies of parts weren't being pilfered and sold for vodka, or just as parts of "rob Peter to pay Paul" schemes to get supplies where they actually were needed, rather than where the Plan said they ought to be needed.
It's possible that fifty or even eighty percent of Soviet nuclear munitions would've failed to operate in an actual nuclear war -- and that's assumed that their delivery systems would actually work, especially as they came to rely more and more on missiles rather than bombers with human pilots to fly them to the target. But while that would've greatly reduced reduced the carnage, there's still the question of whether the shock of losing whole cities in a flash would outweigh the morale boost of seeing the egg on the face of the vaunted Soviet military when dud bombs went clunk in the middle of American cities, and at most required some hazmat cleanup for scattered radioactive materials.