author
Little is known for certain about this late Roman writer, but his compact guide to army organization and discipline became one of the most influential military books in Europe for centuries. He is also remembered for preserving the famous idea that preparing for war can help secure peace.

by de Pisan Christine, Honoré Bonet, Sextus Julius Frontinus, Flavius Vegetius Renatus
A writer of the later Roman Empire, Vegetius is usually placed in the late 4th century. The details of his life are uncertain, and modern accounts rely mostly on what can be gathered from his surviving works rather than from independent biographical records.
His best-known book is the Epitoma rei militaris—often called De re militari—a handbook on recruitment, training, discipline, tactics, and siegecraft. He also wrote the Digesta Artis Mulomedicinae, a work on veterinary medicine focused on caring for horses and mules.
Vegetius had an unusually long afterlife for an ancient author. His military treatise was copied, translated, and studied throughout the Middle Ages and beyond, shaping European ideas about warfare, discipline, and leadership long after the Roman world had changed.