Kant's efforts as a philosopher for peace are widely known. It is noteworthy, however, that despite the attention given to his essay "Perpetual Peace" ("Zum ewigen Frieden"), little work has been produced regarding Kant's thoughts on violence and war in the state of nature. The present work is an attempt to balance this lack of research by answering the question of legitimate violence in the state of nature in the work of Kant. Particularly challenging for this investigation will be to supplement Kant at many places with the help of his own theoretical system, since he never advanced his own theory of violence. It will then be considered which kinds of violence must be allowed in the state of nature between individuals in accordance with the Kantian law of reason. Following this, a detailed interpretation of the martial law from the "Doctrine of Right" ("Metaphysische Anfangsgründe der Rechtslehre"). Of interest here is the analysis of legitimate violence between states in the form of wars. Finally, this work would be incomplete if Kant's statements on war from his aesthetics and the history of philosophy were not also considered, which appear to stand directly against its lawful and ethical prescriptions.