In this paper, we argue that the greater accountability of democratic leaders to their citizens creates powerful pressures on leaders to reduce the human costs of war. In an analysis of a new dataset of fatalities in interstate wars (1900 to 2005) we find that highly democratic states suffer significantly fewer military and civilian fatalities. We argue that democracies limit their war losses primarily by adopting four specific foreign and military policies. First, democracies generate higher military capabilities than nondemocracies in times of war. Second, democracies are more likely to augment their national capabilities by joining more powerful coalitions of states during war. Third, democracies are more likely than other states to utilize battlefield military strategies that minimize their fatalities. Finally, democracies are more likely to fight wars on battlefields that are not contiguous to their home territories, thereby shielding their civilian populations from the fighting.A rough consensus has emerged in the literature on the ''democratic peace'' that, contrary to the expectations of early theorists like Immanuel Kant, democracies are not generally more pacific than nondemocracies. As modern scholars have recognized, the fact that elected leaders are more accountable to the citizens who must bear the costs of wars does not imply that these leaders will avoid wars in general-only that they will oppose highly unpopular wars that threaten their tenure in office.Recognizing this, recent studies of democratic war involvement have focused on war outcomes (defined in terms of victory and defeat) as a central concern of democratic leaders in times of war. We argue, however, that democracies should be highly attentive to the costs of war as well as its outcome; they do not seek victory at any price. Moreover, because victory is sometimes won only through a heavy price in blood and treasure, a war's outcome is not a reliable proxy for its costs. Thus, more than two centuries after it was articulated, one of the key implications of Kant's theory-that democracies should strive to minimize the costs borne by their citizens-has not been adequately tested.With this in mind, in this article we develop a refined theory of democratic war behavior and utilize a newly constructed dataset on war fatalities to conduct the most rigorous test of this theory to date. We find that highly democratic states suffer fewer military and civilian casualties in their wars than do other states. More importantly, however, we also shed new light on precisely how democracies reduce the costs of the wars they fight, a critical theoretical question largely ignored by the existing literature on the democratic peace. We argue that democracies limit their losses by adopting four key foreign and military policies that help them minimize both military and civilian fatalities-mobilizing superior military forces in times of war, utilizing casualty-reducing military strategies on the battlefield, fighting battles on distant territories and fightin...