In the field of international studies, the liberal school of international relations (IR) has proposed a series of theories of peace, with democratic peace theory emerging as the most robust and compelling. Since the 1990s, a vast literature has provided empirical corroboration of the separate zone of peace created by democracies. The proposition that democracies rarely engage in war with each other has been validated by historical evidence and quantitative studies. The restraints imposed on democracies by domestic institutional and constitutional arrangements, the political culture of liberal leaders, and the interdependencies fostered by open market economies have been identified as the explanatory factors. However, despite substantial empirical evidence, the democratic peace theory has been increasingly questioned in many ways, from both methodological and political-normative perspectives. Considering the challenges confronting democracy in the current world order, coupled with the resurgence of great power competition and warfare, the democratic peace theory has shown all its weaknesses.