I don’t have anything substantive add to the excellent summary by Gray Ghost except that according to McNamara, in an exchange he had with Fidel Castro at the 1991 Ibero-American summit, the latter admitted that has the US attemtped an invasion of Cuba he would have requested the Soviet use of tactical nuclear weapons in defense. Most scenarios of the use of tactical nukes in this context typically lead to some degree of strategic exchange as well, and in fact, most ‘unrestricted’ simulations of nuclear warfare end up with a full-up exchange of weapons out of fear that delaying response will mean losing the ability to respond, e.g. being subject to a counterforce attack.
Of course, in 1962, the degree of response with the limited arsenal and poor accuracy and reliability of delivery systems would have provided some limit to the effectiveness, albeit more significant. Even in the heyday of Soviet nuclear arsenals in the late 'Seventies and early 'Eighties, the US, much less the world, would not have been completely destroyed despite hyperbolic claims, but the industrial and agricultural capacity would have certainly been diminished, potentially pushing back the technical capability to pre-Industrial levels. (This is especially true if a concerted EMP attack were made which could render the electrical production and distribution infrastructure unuseable.) We can say with some degree of confidence that an exchange between US/NATO and the Soviet Union/Warsaw Pact would have left both superpowers significantly diminished and most of Europe damaged and impoverished.
It should be noted that while there is no longer a Soviet Union or Warsaw Pact, and the effectiveness of the Russian nuclear arsenal is suspect at best, the spectre of nuclear war still remains, Even with the START reduced inventories and elimination of short and intermediate range nuclear armed ballistic missile systems, both Russia and China have the capability to reach the continental US (CONUS) and Europe. India and Pakistan have been in conflict to the point that the use of nuclear weapons in a regional exchange has been considered by pundits. Israel has a substantial, if not officially acknowledged, nuclear arsenal. Iran has sought the capability to make enriched nuclear material and has improved their ballistic missile technology (although it is not terribly reliabie and could not reach CONUS or likely even Europe). North Korea’s nuclear program is more saber-rattling than serious, but it is enough to keep US-ally South Korea nervous.
And the technology to build nuclear weapons from what are essentially off-the-shelf components is within reach of even a small group of technical people with funding from a government or large criminal organization. Despite decades of research and testing, not a single anti-ballistic missile system has been shown to be effective against ICBM-class vehicles, and has arguably limited effectiveness even at the theatre defense level against a mass or unanticipated attack, nor can any ABM system defend against unconventional attacks. The need for effective non-proliferation efforts, along with the recognition that we will never live in a truly “nuclear-free world” must be acknowledged and pursued. A single exchange, even at a regional level, could result in the deaths of tens of millions of people, critical loss of ariable land, and massive destabilization.
One thing we got out of the Cuban Missile Crisis, having approached so closely to that cliff, was a recognition of the need to avoid engaging in conflicts that could directly lead to a nuclear exchange, and the necessity of having robust communications with an enemy in hopes of being able to defuse a conflict before mushrooms started growing over Omaha and Colorado Springs, and their counterparts in the East.
Stranger