In *A History of Warfare*, Keegan outlines the development and limitations of warfare from prehistory to the modern era. It looks at various topics, including the use of horses, logistics, and "fire". One key concept put forward is that war is inherently cultural. In the introduction, he rigorously denounces the idiom "war is a continuation of policy by other means", rejecting on its face "Clausewitzian" ideas
Sir John Desmond Patrick Keegan was a British military historian, lecturer, writer and journalist. He was the author of many published works on the nature of combat between the 14th and 21st centuries concerning land, air, maritime, and intelligence warfare, as well as the psychology of battle. - Wikipedia