Explaining incompleteness and conditionality in alliance agreements

What explains the form of international alliances? Conventional wisdom forecasts that audience cost-averse states like democracies demand that their alliances include conditions, such as limitations to specific regions, to reduce the likelihood of paying the audience costs of treaty violation. This paper builds on the conventional wisdom by proposing that democracies are especially likely to demand that an alliance include conditions that make the treaty more incomplete, that is, make the compliance requirements more ambiguous, in comparison to including conditions that do not make the treaty more incomplete. Treaty incompleteness gives leaders another tool to reduce domestic political audience cost risks. Incompleteness makes it easier for a leader to argue to a domestic political audience that a wider array of actions, including actions such as nonintervention on behalf of an embattled ally that other signatories might view as noncompliant, is actually compliant, reducing domestic audience costs for these actions. Examining all international alliances since 1816 using seemingly unrelated regression, the paper finds empirical support for the theory: alliances with democracies are more likely to have conditions making the treaty more incomplete, but not more likely to have conditions that do not make the treaty more incomplete.