This article offers a reconstruction of Nietzsche's critique of Kant's scheme for perpetual peace distilled from his life-long confrontation with Kant's critical philosophy. Through this reading strategy, it sheds light on Nietzsche's controversial and yet surprisingly under-researched reflections on the problem of conflict and war in human affairs. Although Nietzsche embraced many of the basic premises of Kant's critical philosophical project, he considered the ethico-political conclusions Kant drew from these to be both irrational and nihilistic. From Nietzsche's perspective, Kant's thoughts on politics and International Relations rest on a fundamental misunderstanding of the phenomena of agency, statehood, and war that elides both the tragic relationship between politics and culture, and the violence which Nietzsche believes to be latent in all attempts at reconciling individual with collective autonomy. According to Nietzsche, Kant's influential association between liberal republicanism, freedom, and peace contributed unwittingly in ushering in the cult of the nation-state, which Nietzsche warned would engulf Europe into a wholly new kind of organised violence in the coming decades. Although clearly not without their uncritical assumptions and hubristic tendencies, Nietzsche's reflections on war and peace draw attention to some of the more insidious risks and difficulties attending liberal attempts at accommodating cosmopolitan values and principles within the framework of the modern nation state.