A person’s behavior is rational if it is in his best interests, given his information. - Robert Aumann

The players in a game are said to be in strategic equilibrium (or simply equilibrium) when their play is mutually optimal: when the actions and plans of each player are rational in the given strategic environment – i.e., when each knows the actions and plans of the others.

"Interactive Decision Theory" would perhaps be a more descriptive name for the discipline usually called Game Theory.

It turns out that the Romans were champs in making peace. Their motto was that if you want to make peace, you need to prepare for war. They knew game theory.