Two Against One: Deterrence in the Triad

This essay explores a deterrence relationship between one defender and two challengers that are interconnected game-theoretically but are otherwise acting independently. In the double deterrence game model, the primary challenger makes the first move, defender, the second, and the secondary challenger makes its move only after the defender and the primary challenger have made their choices. In other words, the threat of the secondary challenger is both latent and contingent. There are four types of defenders, and three types of the two challengers. These preference assumptions define 36 distinct strategic environments, or games. These games are analyzed under both complete and incomplete information. The results are highly sensitive to the specific combination of player types. Deterrence is most likely to succeed when a defender’s threat is highly credible, and to fail when it is low. The secondary challenger is most likely to have an impact on play only at intermediate levels of the defender’s and the primary challenger’s credibility. Assuming a rising challenger, or a declining defender, or both, a danger zone will exist just prior to, or immediately after, the primary challenger has achieved parity with the defender, that is, when a balance of capabilities exists. The principal aim of a defender of the status quo facing two challengers acting independently should be on preventing a challenge by its primary opponent. This conclusion is robust no matter what configuration of player types one assumes.