But suppose the two games are simultaneously up for decision, and the same two parties are involved in both. If either party can commit himself to a threat he may improve his position. East, for example, could threaten to choose β rather than B in game 6, unless North chose A rather than α in game 5; alternatively, North could threaten α in game 6 unless East chose β in game 5. Assuming the intervals large enough in game 6, and the threat persuasively committed and communicated, the threatener gains in game 5 at no cost in game 6. Because his threat succeeds he does not carry it out; so he gets AB in 6 as well as his preferred choice in game 5. To express this result differently, game 6 supplies what was ruled out earlier, namely, the threat of an act “outside the game.” From the point of view of game 5, game 6 is an extraneous act, and East might as well threaten to burn North’s house down if he does not choose A in 5. But such purely extortionate threats are not always easy to make; they often require an occasion, an object, and a means of communication, and additionally often suffer from illegality, immorality, or resistance out of sheer stubbornness. The joining of two negotiations on the same agenda may thus succeed where a purely gratuitous threat would be impracticable.

XREF: Connects to game theory and commitment strategies, linking to Schelling's broader work on strategic moves and credible commitment.

Thomas C. Schelling, The Strategy of Conflict, loc. 128