cially if they had any reason at all to suspect that the president was not sane. And there is no reason to suppose that the Russian military is any different in this respect from the American.
But nuclear war can also come in a world in which destruction is both mutual and assured even if the leaders of both sides are perfectly sane. Consider a crisis that neither side sought but resulted from events that spiraled out of control -- a Cuban missile crisis that got out of hand. A series of miscalculations might convince one side or the other that its choice was between being destroyed by the other's first strike or striking first in a preemptive blow, a choice that was seen as being between utter, total destruction on the one hand and, on the other, horrendous casualties but enough survivors to constitute a viable nation and society.
And nuclear war can even more easily come in the midst of a crisis because of a series of mistakes and miscalculations on one side and then the other, as the Cuban missile crisis so vividly demonstrated. One move can logically lead to another until both sides suddenly find themselves in the midst of a war. At the outbreak of World War I, the former German chancellor Prince Bernard Von Bülow is supposed to have said to his successor, "How did it all happen?" The reply was, "Ah, if we only knew!"
Mutual assured destruction is a powerful deterrent, in other words, but it is not a guarantee. In a MAD world, nuclear war may come later rather than sooner, but if humankind can do no better than mutual assured destruction to deter nuclear war then sooner or later nuclear war will surely come.