What utility does ancient military history have for the development of modern theories of warfare? This monograph discusses the development of theory from ancient history by examining the theories and writings of United States Air Force Colonel (retired) John Boyd. Ancient history is useful for development of modern military theories. Ancient history played a significant role in the development of his theories on maneuver warfare. The abstract concepts he synthesized provide valuable instruction to modern operational artists on how to use ancient history in the development of their own theories and doctrine. Boyd arrived at the past with his theories in mind and then went searching for proof. He effectively linked concepts from the Battle of Cannae, among others, and the Mongol invasion of Europe. From these historical examples, Boyd showed how maneuver and moral warfare developed and how inferior forces used these styles of warfare to defeat superior opponents.