The relationship between democratization and war has recently sparked a lively debate. We find that transitions from autocracy that become stalled prior to the establishment of coherent democratic institutions are especially likely to precipitate the onset of war. This tendency is heightened in countries where political institutions are weak and national officials are vested with little authority. These results accord with our argument that elites often employ nationalist rhetoric to mobilize support in the populist rivalries of the poorly-institutionalized democratizing state but then get caught up in the belligerent politics that this process eventually unleashes. In contrast, we find that transitions that quickly culminate in a fully coherent democracy are much less perilous. Further, our results refute the view that transitional democracies are merely the targets of attack due to their temporary weakness: in fact, they tend to be the initiators of war. We also refute the view that any regime change is likely to precipitate the outbreak of war: transitions toward democracy are significantly more likely to generate hostilities than transitions toward autocracy.