Many problems in nuclear strategy are unpleasant or even horrifying to contemplate. As the number of nuclear-armed nations grows, the chances that one will be put in a desperate situation and choose to use one more more nuclear weapons likely rises.
An article by Vince Manzo and John Warden considers potential American responses to the use of a nuclear weapon by a hostile power, including four scenarios involving North Korea and Russia.
Among all the international norms under threat, the norm of non-use of nuclear weapons is among the most valuable. If at all possible, it should be reinforced even if one state does use nuclear weapons. As the article illustrates, however, that will be one among many strategic considerations, and no option offers the kind of certainty that would be desirable.