Democratic victory and war duration: Why are democracies less likely to win long wars?

The probability of democracies winning wars appears negatively associated with the duration of wars. This relationship might be explained by two contrasting mechanisms besides the selection effect. According to one mechanism, democracies require a long time to reach a surrender decision, because they face audience costs if they break a prewar commitment hastily. The other mechanism suggests that democracies are less likely to win prolonged wars, because their battlefield effectiveness declines over time. To explore these ideas, we develop game-theoretic models of war incorporating democratic citizens and soldiers. Although the two mechanisms diametrically differ in their logic, the models based on them yield similar predictions about military-strategy choices. These predictions are consistent with empirical findings indicating that while democracies increase their likelihood of victory through maneuver strategies, autocracies display mixed incentives between maneuver and attrition strategies. These results suggest that both mechanisms may influence how democracies conduct wars.