This article uses a laboratory experiment to explore how groups’ internal rules for leader selection affect how leaders select into and fight conflicts. The findings reveal that, counter to expectations, leaders of democratic groups were more likely than leaders of autocratic groups to select into a conflict rather than accept a negotiated settlement. Conditional on conflict occurring, democratic leaders did not mobilize more resources for war than autocratic leaders. However, democratic leaders were less likely to accept a settlement once a war was underway and they expended more effort in the last round of conflict, suggesting once they entered a war they fought for a decisive victory. Domestically, democratic leaders were punished for losing wars more often than autocratic leaders, while winning wars did not benefit democratic leaders significantly.