This research has a two-fold purpose. The first, historical in nature, is to clarify the manner in which Immanuel Kant’s thought was transmitted to the military theorist Carl Von Clausewitz. This will involve examining the writings and lectures of J. G. Kiesewetter, who, as one of Kant’s favourite students as well as one of Clausewitz’s teachers, acts as a direct link between the two. The second purpose, which is more philosophical in orientation and which will be facilitated by the research conducted as part of the first purpose, seeks to pursue the implications of the assertion (implicit in Kant’s texts and insisted upon by Clausewitz) that the concept of actuality is prior to the concept of possibility. The dominant strain of post-Kantian thought, ‘German Idealism’, conceives of actuality as the mere realisation of something possible. The German Idealists hence accorded a certain privilege to possibility and the corollary idea of freedom. They further, often presuppose possibility and use as a starting point for their philosophical investigations. Clausewitz precisely criticised German Idealism for calmly stepping out of actuality into the pure realm of abstraction and possibility. For him there is nothing outside of actuality, even possibility itself is produced, manipulated, and destroyed within actuality. By pursuing this obscure suggestion this research intends to draw out and develop the strange and as yet unexplored metaphysics which lingers behind Clausewitz’s writings on war, a metaphysics characterised by decomposition and reorganization, one which is constantly attempting to produce stability by means of strategy, in the face of uncertainty and chance. The tracing of a different trajectory of Kantian philosophy will produce a new field of problems while also allowing a critical examination of many of the ones that have dominated the history post-Kantian thought right up to the present.