American nuclear use policy has always been a mixture of making noises like it was inevitable but with the reservations that everything had to be approved by the sitting President. So on the one hand, for the purposes of deterrence, the US tried to signal very clearly that it would in fact use nuclear weapons, at least tactical ones, in the event of any significant Soviet military action in Western Europe. And it took this fairly seriously; all of the war games that the US played during this period more or less assumed that nuclear weapons would be liberally used. But again, the structure of US nuclear forces is that in principle all nuclear use had to be personally approved by the President, and it is hard to know what a President would do under the circumstances, especially since most nuclear force options were extremely inflexible (all-or-nothing proposals that would all but guarantee an all-out Soviet nuclear second strike attack). At times this sort of nuclear decision-making was "pre-delegated" by the President (Eisenhower did this) so that local commanders could, under their own authority, use tactical nuclear weapons under emergency conditions. But in general the civilian authorities have jealously guarded the decision to use the bomb, for reasons that are fairly obvious. (At times that took different forms — in the very earliest days of the nuclear age, the military was not even allowed to have the fissile material of the bombs without explicit command; the cores were kept under armed guard in separate, civilian-run facilities on the military bases. Later designs in weaponry made this arrangement infeasible, however.)