The Roman army is recognised as one of the most effective fighting machines that the world has ever seen. However, the senior officer corps of the Roman army was essentially amateur, made up of aristocratic men pursuing political careers. What then was the secret of the Romans' success? Kate Gilliver provides the first comprehensive study of military theory - as well as practice - in the late Republic and early Empire. She draws not just on the ancient textbooks, but makes use of the other contemporary literary evidence and on the wealth of archaeological evidence for military activity. In five central chapters Dr Gilliver looks in detail at all aspects of the Roman army; at its organisation, the order of march, temporary encampments, pitched battles and siege warfare. These chapters reveal the army's very flexible organisation and skills, as well as it discipline. The book also contains a fine range of illustrations, an Appendix of all the key Roman military treatises and a full Glossary of key technical terms. The complete work will command a wide international readership, particularly among military historians, archaeologists and wargamers.