According to the democratic peace theory, democracies are hesitant to engage in armed conflict with other identified democracies. Contrary to theories explaining war engagement, it is a “theory of peace” outlining motives that dissuade state-sponsored violence. The proposition that democracies are more peaceful than autocracies has spawned a huge literature. Much of the relevant quantitative research has shown that democracies indeed rarely, if ever, fight each other, although they are not necessarily less aggressive than autocracies in general. Although, statistically, the probability of war between any two states is considerably low, the absence of war among liberal democracies across a wide range of different historical, economic, and political factors suggests that there is a strong predisposition against the use of military violence between democratic states. According to scholars, the democratic peace theory can elaborate on the empirical phenomena previously explained by the earlier dominant research program, realism in international relations; in addition, the initial statement that democracies do not, or rarely, wage war on one another, has been followed by a rapidly growing literature on novel empirical regularities. This democratic peace proposition not only challenges the validity of other political systems, but also the prevailing realist account of international relations, which emphasizes balance-of-power calculations and common strategic interests.