Democratic states are in general about as conflict- and war-prone as nondemocracies, but democracies have rarely clashed with one another in violent conflict. We first show that democracy, as well as other factors, accounts for the relative lack of conflict. Then we examine two explanatory models. The normative model suggests that democracies do not fight each other because norms of compromise and cooperation prevent their conflicts of interest from escalating into violent clashes. The structural model asserts that complex political mobilization processes impose institutional constraints on the leaders of two democracies confronting each other to make violent conflict unfeasible. Using different data sets of international conflict and a multiplicity of indicators, we find that (1) democracy, in and of itself, has a consistent and robust negative effect on the likelihood of conflict or escalation in a dyad; (2) both the normative and structural models are supported by the data; and (3) support for the normative model is more robust and consistent.

The classical liberals believed that democracy and free trade would reduce the incidence of war. Here we conduct new tests of the `democratic peace', incorporating into the analyses of Maoz & Russett (1993) a measure of economic interdependence based on the economic importance of bilateral trade. This allows us to conduct a simultaneous evaluation of the effects of regime type and interdependence on the likelihood that a pair of states will become involved in a militarized interstate dispute. We control in all our analyses for a number of potentially confounding influences: growth rates in per capita income, alliances, geographic contiguity, and relative power. Our logistic regression analyses of politically relevant dyads (1950-85) indicate that the benefits of the liberals' economic program have not been sufficiently appreciated. Trade is a powerful influence for peace, especially among the war-prone, contiguous pairs of states. Moreover, Kant (1991 [1795]) was right: International conflict is less likely when external economic relations are important, executives are constrained, and societies are governed by non-violent norms of conflict resolution.

This study replicates and extends previous inquiries on the relations between regime type and conflict involvement of states. It examines the robustness of previous findings with respect to various regime attributes, various conflict involvement measures, and units of analysis. Using two comprehensive datasets on polity characteristics and militarized interstate disputes, the empirical analyses reveal: (1) There are no relations between regime type and conflict involvement measures when the unit of analysis is the individual polity (i.e., a state characterized by a certain regime type over a given time span); this finding is robust in that it holds over most regime characteristics and conflict involvement measures. (2) There is a significant relationship between the regime characteristics of a dyad and the probability of conflict involvement of that dyad: Democracies rarely clash with one another, and never fight one another in war. (3) Both the proportion of democratic dyads and the proportion of autocratic dyads in the international system significantly affect the number of disputes begun and underway. But the proportion of democratic dyads in the system has a negative effect on the number of wars begun and on the proportion of disputes that escalate to war.

This article offers an empirical description and discussion of interstate conflict behavior. The basis is a recently completed data set consisting of all recorded instances of threats, displays, and uses of military force among states since 1816. We detail historical trends in the data and describe major dimensions of dispute behavior, including patterns of participation, duration, severity and escalation, regional distribution, and national dispute proneness. The following conclusions are suggested: First, patterns of dispute behavior have been more persistent over time than we often assume. Second, when these patterns have changed, the changes have been evolutionary in nature and have paralleled changes in the size and composition of the interstate system. Third, despite the diversity of the political units that constitute the interstate system, patterns of dispute behavior are generalizable across geographic boundaries.

Scholars increasingly are accepting the empirical generalization that democracies almost never go to war with each other, and infrequently even engage in militarized disputes with each other. It has not been clear, however, whether the rarity of conflict between democracies is caused by some aspect of being democratic, or whether it is caused by some other variable or variables that may be correlated with democracy. Using data on all independent states for the period 1946-1986, we examine the effects of political system type, distance, wealth, economic growth, alliances, and political stability. The results suggest that, although most of the other variables do have an effect, as hypothesized, there still seems to be an independent effect of political system type: democracies engage in militarized disputes with each other less than would be expected by chance. The effect may be enhanced by political stability; that is, states which can be perceived as stable democracies are less likely to be involved in disputes with other democracies.