This ambitious series offers the reader a comprehensive narrative of the military history of the late Roman period from 284 to 641. Each volume (5 are planned) provides a detailed account of the changes in organization, equipment, strategy, and tactics of both Roman forces and their enemies in the respective period, while also offering a detailed yet accessible description of campaigns and battles. Volume I covers the period 284-361, starting with the recovery from the 'crisis of the third century' and the formation of the Tetrarchy. Constantine's civil wars and stabilization are also main themes, with the pattern repeating under his sons. Constantius II's wars against the usurper Magnentius, the Danubian tribes, and the Sassanid Persians illustrate the severe combined internal and external threats the Empire faced at this time. The author discusses these and many other dramatic military events in their full context and draws some interesting conclusions about strategic and tactical developments. He argues, for example, that the Roman transition from infantry to cavalry as the dominant force occurred much earlier than is usually accepted. Anyone interested in the military history of this period will find it both informative and thought-provoking.