De Re Militari by Vegetius is the famous strategy book written in times of the Roman Empire. It explains how they organized their armies, battles, sieges, and war strategies. This is the complete official edition and it contains the 4th part (how to perform sieges, city defenses, and naval warfare) which is not included in commonly available basic editions. De Re Militari is essential to understand European strategy and war due to the fact that, besides describing the military might of Rome in practical terms, it was also used by generals and rulers in the next centuries and the Middle Ages to organize European armies, conduct sieges, reinforce castles, train soldiers, and conquer enemy nations. So much so that generals would be judged and measured in warfare skills by their knowledge and understanding of Vegetius.