The distinctive character of a threat is that one asserts that he will do, in a contingency, what he would manifestly prefer not to do if the contingency occurred, the contingency being governed by the second party’s behavior. Like the ordinary commitment, the threat is a surrender of choice, a renunciation of alternatives, that makes one worse off than he need be in the event the tactic fails; the threat and the commitment are both motivated by the possibility that a rational second player can be constrained by his knowledge that the first player has altered his own incentive structure. Like an ordinary commitment, a threat can constrain the other player only insofar as it carries to the other player at least some appearance of obligation; if I threaten to blow us both to bits unless you close the window, you know that I won’t unless I have somehow managed to leave myself no choice in the matter.

Thomas C. Schelling, The Strategy of Conflict, loc. 293