how realistic was mutually assured destruction in the 50s/60s before the invention of ICBMs? the cuban missile crisis was as close as we've been (so far...) to nuclear war but my understanding is that it was precipitated because there were some medium-range missiles in cuba that could hit part of the US mainland, but not all of it.
let's say arkhipov is overruled and the torpedo is fired - it's the start of nuclear war. how likely is it that it would have actually led to the total nuclear apocalypse situation that "mutually assured destruction" implies?
The idea of "mutually assured destruction" is itself an invention of the 1960s and the ICBM age. Prior to that you have only "deterrence," which is less about mutual vulnerability (much less assured destruction) and more about threatening things that the other state values. In the case of the USA, it was entirely capable of threatening the whole destruction of the USSR and China (early US war plans did not allow the sparing of China), with such overwhelming megatonnage that if something like nuclear winter is possible then it would have certainly occurred. In the case of the USSR, it was capable of threatening total ruin to Europe, but only partial ruin (a few cities, perhaps) of the United States. That was adequate to deter US attacks, even if it was not the total destruction that most people envisage when they think about nuclear war.
Only in the late 1960s and 1970s does something more comparable to parity arise, in which a full-scale nuclear attack would be guaranteed on both the US and USSR.