Woodcut from Vegetius', Four Books of Knighthood, 1511. German translation of De Re Militari (Concerning Military Matters) a treatise by the late Latin writer Publius Flavius Vegetius Renatus about Roman warfare and military principles. The extant text dates to the late 4th, early 5th century. Vegetius based his treatise on descriptions of Roman armies, especially those of the mid to late Republic. It is the only ancient manual of Roman military institutions to have survived intact. The treatise is carefully laid out in subsections. They are organized into four books. The fourth book on siege-craft contains the best description of Late Empire and Medieval siege machines. The German edition updated and included 16th century weaponry some that are quite fanciful.