Deterring Intervention: The Stakes of War and Third-Party Involvement

Abstract

Why does a third party become involved in an ongoing dispute? One important reason for involvement is often the third party's perception that the attacking country poses a significant threat to the status quo. Given the aggressor's aims in the war vis-avis a particular target, the third party worries that the changes wrought by the war will be too extreme. He enters an ongoing war in order to defend the threatened status quo. attacking country, however, chooses the magnitude of the demands she makes of a targeted state. By moderating her demands, she can influence a third party's perception of the threat she poses and thereby influence the third party's willingness to intervene. aggressor's ability to choose the stakes of the war thus creates the interesting possibility that demands can be chosen strategically in order to deter third-party intervention. In this article, I modify the classic extended-deterrence game in order to explore the implications of this strategic logic My modified extendeddeterrence model suggests that the attacker's ability to choose the stakes of war can weaken the third-party defender's ability to deter an attack. An attacker may not be deterred from attacking because the attacker can deter the third party from intervening. model suggests several important implications for both the stakes of war and the probability of third-party intervention. B q lainey (1988) devotes a chapter in his now classic book, Causes of War, to what he calls The Mystery of Wide Wars. His explanation for why some wars in Europe became multilateral while others did not is worth quoting at length. He explains third-party involvement in what originally seemed to be just another regional dispute between Russia and Turkey as follows: It [the Crimean War] began as a war between Russia and Turkey, but the destruction of a division of the Turkish fleet at the Black Sea harbor of Sinope in November 1853 aroused fears that Russia might crush Turkey and so penetrate at last into the Mediterranean and become more powerful than ever before (Blainey 1988, 233, italics mine). He contrasts this multilateral war with two other wars that remained bilateral even though the potential for intervention seemed high: . . the FrancoAustrian [War] of 1859 and the Austro-Prussian [War] of 1866-did not last long enough to establish a decisive superiority on one side. Austria lost both wars but remained a great power; it had not lost by such a margin that the ladder of European power seemed likely to be altered drastically (Blainey 1988, 34, italics mine). Blainey's argument is both noteworthy and novel because he assumes that a third party's incentive to intervene depends very much on what happens inside the conflict. Outsiders intervened in the first instance because they feared that Russia intended to substantially revise the status quo. Intervention did not occur in the latter instances because both France's and Prussia's demands vis-a-vis Austria were modest, resulting in few changes to the status quo. possibility that the decision to intervene in an ongoing dispute is driven in part by what happens inside the conflict creates interesting strategic possibilities that could impact our understanding of the potential diffusion of war. Most important, it raises the interesting possibility that an attacker could intentionally alter his demands in order to influence the likelihood of third-party intervention. As I and others have argued, the stakes of war can often be thought of as endogenous to the conflict (Goemans 2000; Wagner 2000; Werner 1998, 1999). If the stakes of war are strategically chosen, then the classic extended-deterrence relation-