This ambitious series gives the reader a comprehensive narrative of late Roman military history from 284-641. Each volume gives a detailed account of the changes in organization, equipment, strategy, and tactics among both the Roman forces and her enemies in the relevant period, while also giving a detailed but accessible account of the campaigns and battles. Volume I covers the period 284-361, starting with recovery from the 'third-century crisis' and the formation of the Tetrarchy. Constantine's civil wars and stabilization are also major themes, with the pattern repeated under his sons. Constantius II's wars against the usurper Magnentius, the Danubian tribes, and the Sassanid Persians illustrate the serious combination of internal and external threats the Empire faced at this time. The author discusses these and the many other dramatic military events in their full context and puts forward some interesting conclusions on strategic and tactical developments. He argues, for example, that the Roman shift from infantry to cavalry as the dominant arm occurred considerably earlier than usually accepted. Anyone with an interest in the military history of this period will find it both informative and thought-provoking.