The novelty of this reasoning disappears as soon as we recognize that the “balance of terror,” if it is stable, is simply a massive and modern version of an ancient institution: the exchange of hostages. In older times, one committed himself to a promise by delivering his hostages physically into the hands of his distrustful “partner”; today’s military technology makes it possible to have the lives of a potential enemy’s women and children within one’s grasp while he keeps those women and children thousands of miles away. As long as each side has the manifest power to destroy a nation and its population in response to an attack by the other, the “balance of terror” amounts to a tacit understanding backed by a total exchange of all conceivable hostages. We may not, of course, want to exchange quite that many hostages in support of this particular understanding with this particular enemy. But in a lawless world that provides no recourse to damage suits for breach of this unwritten contract, hostages may be the only device by which mutually distrustful and antagonistic partners can strike a bargain.

XREF: Frames nuclear deterrence as a variant of hostage exchange, linking international relations to older legal and customary practices. Pays off: "Hostage-taking structurally parallels wine-sharing and public gang meetings"

Thomas C. Schelling, The Strategy of Conflict, loc. 545