Nuclear offense and defense are related in complicated ways. Nor can they be disengaged from the issue of conventional war. The last chapter argued that any war in Europe, and other shooting matches between superpower general purpose forces, would be a nuclearized conventional war. The threat of nuclear war would be uppermost in the minds of American and Soviet policy makers even before war broke out. Neither superpower can threaten conventional war in conventional terms any longer.
This begs the question of the larger role of deterrence, if any, in preventing war. This question might seem surprising since it is a truism among military strategists that nuclear weapons serve mainly to deter wars in order not to have to fight them. But the matter is not so simple, for some argue that a credible deterrent depends on a persuasive ability to fight a war. By this reasoning, if it is nuclear war that we are aiming to deter, then we are required to possess a nuclear war fighting capability. Another school of thought suggests, to the contrary, that deterrence in the nuclear age requires far less than the ability to fight a nuclear war to anything approaching a successful conclusion. The probability of successful nuclear war is nil, according to this school, and deterrence is the stronger for it. What matters is the ability of either side to wreak havoc on the society of the other in retaliation for whatever crime has been committed against it.
Three issues must be addressed before the role of deterrence between superpowers in the nuclear age can be parsed effectively: (1) whether deterrence depends on rationality, and what rationality means, (2) the distinction between what it is rational to do in deterring an opponent