Clausewitz’s concepts of grammar and logic have stood the test of time. His dictum that war is indeed “the continuation of policy by other means” holds true today, and while the character of war has evolved, the higher logic and the influence of policy has remained a constant. This article will first address some key definitions, before exploring the concept of logic and grammar as introduced in On War and as they relate to his own experiences. These concepts will then be explored through the prisms of two contrasting case studies: industrialised warfare on the Western Front during the First World War, and the new logic of war in the face of the unprecedented existential threat of the Nuclear Age.