Alliances, Credibility, and Peacetime Costs

Abstract

Alliances are not perfectly credible. Although alliances raise the probability of intervention into war, many allies do not honor their promise in wartime. A formal model of alliances as signals of intentions to explore the credibility of alliances is presented. One state threatens another. A third state shares an interest with the second in preventing the demands of the first. A simple model of a crisis among these three is solved first without an alliance between the second and the third states. The author then allows them the chance to form an alliance before the crisis. Alliances have two effects: (1) the ability of the allies to fight together is increased, and (2) peacetime costs on the allies are imposed. The model with alliances produces a wide range of strategic behaviors. The implications of the model for the formation, credibility, and deterrent effects of alliances are broadly consistent with stylized facts in the literature.

Treaty Compliance and Violation

“…Formal alliances have generally been theorized as signals of a state's intent to intervene militarily under certain conditions should war erupt (Morrow 1994). As such, they are generally signed with the expectation that they will be complied with in case of war.…”

A winning proposition? States’ military effectiveness and the reliability of their allies

“…Leeds (2003) sets up the mismatch between formal work on alliances and empirical findings on alliance violation. Morrow (1994) describes alliances as costly signals of common interests among allies. In his model, states with common interests form alliances to signal those interests in the face of uncertainty about whether they would intervene on one another's behalf, and these alliances are expected to be credible because of their significant peacetime costs (Morrow, 1994, pp.…”

“…Alliances involve costs for all members and thus are not likely to be entered into lightly, and yet the existence of alliance violations in world history is indisputable. Formal theoretical work on alliances by Smith (1995Smith ( , 1996, Morrow (1994) and Fearon (1997) offers models that expect no violation of alliances or very infrequent violation of alliances, even though empirical work has established that formal alliances are violated approximately 25 percent of the time (Leeds et al, 2002).…”

Alliances in the Shadow of Conflict

“…Many more examples 1 See Kimball (2006) and Johnson and Leeds (2011) for recent surveys and further empirical analyses. Formal model analysis on alliances include, for instance, Morrow (1991Morrow ( , 1994Morrow ( , 2000 and Niou and Ordeshook (1994). Mattes and Vonnahme (2010) analyze non-aggression pacts as a special type of alliance.…”