In This Article Expand or collapse the "in this article" section Democratic Peace Theory

  • Introduction
  • General Overviews
  • Early Empirical Work
  • Democracy and War Outcomes
  • Democracy, Alliance, and Wars
  • Democracies, Conscription, and War
  • Normative Accounts
  • Systemic Outlooks and the Effect of Peace on Democracy
  • Constructivist Accounts
  • Qualitative Empirical Scholarship
  • Formal Theory
  • Data Sets

Political Science Democratic Peace Theory
Dan Reiter
  • LAST REVIEWED: 02 May 2019
  • LAST MODIFIED: 25 October 2012
  • DOI: 10.1093/obo/9780199756223-0014


Democratic peace is the proposition that democracies are more peaceful in their foreign relations. This idea dates back centuries, at least to Immanuel Kant and other 18th-century Enlightenment thinkers. In recent decades it has constituted a major research agenda, competing with and arguably supplanting other research agendas such as neo-realism. The democratic peace proposition has many possible empirical and theoretical forms. On the empirical side, some propose that democracies are more peaceful in their relations with all other states in the system (“monadic” democratic peace); some propose that democracies are more peaceful only in their relations with other democracies (“dyadic” democratic peace); others argue that the more democracies there are in a region or the international system, the more peaceful the region or international system will be (“systemic” democratic peace); and still others doubt the existence of any significant relationship between democracy and peace. Notably, most although not all empirical research on the democratic peace has employed quantitative methods of analysis. On the theoretical side, there are many different accounts of the relationship between democracy and peace, with most focusing on domestic political institutions, domestic political norms, and constructed identities. The democratic peace proposition is connected to many other propositions linking domestic politics and international relations, including that democracies are more likely to cooperate with each other, that democracies are more likely to win the wars they fight, that escalating military casualties degrade public support for war, that leaders initiate conflict to secure their domestic hold on power (the diversionary hypothesis), that democracies fight shorter wars, that different kinds of democracies experience different kinds of conflict behavior, that different kinds of authoritarian systems experience different kinds of conflict behavior, and others. The democratic peace also overlaps with related ideas such as the liberal peace and the commercial peace.

General Overviews

The democratic peace proposition has been lurking in Western thought for millennia, as Weart 1998 shows, but Kant 1991 provides its first modern formulation. The idea that global democracy would provide a solid foundation for global peace was restated in 1917 by Woodrow Wilson as a justification for American entry into World War I and then as part of his vision for a new world order. Modern political science first observed the dyadic democratic peace—that democracies tend not to fight each other—in the 1970s. The observation enjoyed greater attention in the 1980s in particular in two pathbreaking 1983 essays by Michael Doyle, reprinted in Doyle 2011. It received fuller theoretical and empirical attention in the 1990s. Fukuyama 1992, a famous argument that humanity had reached “the end of history,” incorporates the democratic peace proposition. Other scholars sought to develop the theory and push forward more advanced research designs in works such as Russett 1993; Ray 1995; and Rousseau, et al. 1996. In the 2000s, proponents of the democratic peace responded to their critics and embedded the democratic peace in a broader Kantian peace (Russett and Oneal 2001).

  • Doyle, Michael W. Liberal Peace: Selected Essays. New York: Routledge, 2011.

    Contains a number of Doyle’s important essays, especially from the 1980s, that lay out the philosophical and theoretical basis of the democratic peace.

  • Fukuyama, Francis. The End of History and the Last Man. New York: Free Press, 1992.

    Presents a Hegelian argument that humanity has at last achieved its penultimate form of political and economic organization, liberal democracy. The definitive intellectual statement that Western values triumphed in the Cold War.

  • Huth, Paul K., and Todd L. Allee. The Democratic Peace and Territorial Conflict in the Twentieth Century. Cambridge, UK: Cambridge University Press, 2002.

    Application of the democratic peace to territorial conflict in the 20th century. Presents a massive new data set on territorial conflicts.

  • Kant, Immanuel. Kant’s Political Writings. 2d ed. Edited by Hans S. Reiss. Cambridge, UK: Cambridge University Press, 1991.

    Central essay is on the “perpetual peace,” which presents Kant’s vision as to how republics can maintain world peace. Originally published in 1796.

  • Ray, James Lee. Democracy and International Conflict: An Evaluation of the Democratic Peace Proposition. Columbia: University of South Carolina Press, 1995.

    Provides an extensive literature review on democratic peace literature up to the early 1990s as well as case studies of the Fashoda Crisis and Spanish-American War.

  • Rousseau, David L., Christopher Gelpi, Dan Reiter, and Paul K. Huth. “Assessing the Dyadic Nature of the Democratic Peace, 1918–1988.” American Political Science Review 90.3 (1996): 512–533.

    DOI: 10.2307/2082606

    Important, early empirical test of the democratic peace, presenting important research design advances.Available online by subscription.

  • Russett, Bruce. Grasping the Democratic Peace: Principles for a Post–Cold War World. Princeton, NJ: Princeton University Press, 1993.

    The first book-length treatment of the democratic peace. Lays out the normative and institutional explanations of the democratic peace and presents a variety of different forms of rigorous evidence demonstrating the dyadic democratic peace, including sophisticated analysis of post-1945 conflict behavior.

  • Russett, Bruce, and John R. Oneal. Triangulating Peace: Democracy, Interdependence, and International Organizations. New York: Norton, 2001.

    Embedded the democratic peace in a larger theoretical framework, the Kantian Peace, in which democracy, trade, international organization, and peace all mutually reinforce each other. Presented more sophisticated empirical tests, addressing many 1990s theoretical and empirical critiques. Also see Democratization.

  • Weart, Spencer R. Never at War: Why Democracies Will Never Fight One Another. New Haven, CT: Yale University Press, 1998.

    Summarizes several years of work on democratic peace theory. Presents a narrative rather than statistical empirical tests. One main contribution is the analysis of democratic peace in pre-Napoleonic times, including ancient Greece and medieval Italy. Discusses the phenomena of democratic aggression and imperialism.

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