The article considers the modern meaning of Kant’s doctrine of war. The author examines the context and content of the key provisions of Kant’s concept of perpetual peace. The author also reviews the ideological affinity between Kant and previous authors who proposed to build alliances of states as a means of preventing wars. It is noted that the French revolution and the wars caused by it, the peace treaty between France and Prussia served as the historical background for the conceptualization of Kant’s project. In the second half of the 20th century, there is a growing attention to Kant’s ethical and political philosophy. Theorists of a wide variety of political and ethical schools, (cosmopolitanism, internationalism, and liberalism) pay attention to Kant’s legacy and relate their own concepts to it. Kant’s idea of war is reconsidered by Michael Doyle, Jürgen Habermas, Ulrich Beck, Mary Kaldor, Brian Orend. Thus, Doyle tracks democratic peace theory back to Kant’s idea of the spread of republicanism. According to democratic peace theory, liberal democracies do not solve conflict among themselves by non-military methods. Habermas, Beck, Kaldor appreciate Kant as a key proponent of cosmopolitanism. For them, Kant’s project is important due to notion of supranational forms of cooperation. They share an understanding that peace will be promoted by an allied authority, which will be “governing without government” and will take responsibility for the functioning of the principles of pacification of international relations. Orend’s proves that Kant should be considered as a proponent of the just war theory. In addition, Orend develops a new area in just war theory – the concept of ius post bellum – and justifies regime change as the goal of just war.