With respect to SLBM, they are less prone to destruction in normal warfare. What happens if an enemy destroys a ballistic submarine? Do you go to nuclear war ov

With respect to SLBM, they are less prone to destruction in normal warfare. What happens if an enemy destroys a ballistic submarine? Do you go to nuclear war over that? What about two? The only way that I see this question arising is if there were direct, open warfare with another highly capable nuclear weapons state. But if the US has gone to war with such a NWS, I think that the logic of rational deterrence has already failed on at least one side -- even if neither side has yet used nuclear arms. Outcomes after that point can't be calculated on the basis of rational cost-benefit analysis because rationality is no longer the driving force. I find the logic of mutually assured destruction sound as far as it goes. Empirically, it seems correlated with a long period free of (direct) warfare between great powers. But I fear that this mechanism is brittle. It's one accident or leadership cognitive error away from shattering.