Books like The late Roman army by Pat Southern

Edward Gibbon’s monumental history of Rome, compressed into a single volume, traces the empire’s rise and fall while highlighting religion’s influence and the rise of Islam.

Facing unprecedented pressures from within and without, in the early fourth century A.D. the Emperor Constantine formed a new military force, a permanent Roman field army. He levied detachments from his legions defending the frontiers, and in a drastic step with far-reaching consequences, he recruited soldiers from the unconquered Germans east of the Rhine. Those new detachments of auxilia gave the western Roman army a strongly Germanic, but basically loyal character. Was Constantine's decision one of the major causes of the fall of the Western Empire? Dr. Cromwell argues that misuse of that army by later generals who wanted to intimidate their enemies rather than defend the empire led to the final economic and military disasters. Using original charts and clear explanations of terms, Cromwell shows both how the Roman field army was organized and why it was initially successful. He also illustrates the geographical and political differences which made the Eastern Empire based on Constantinople more viable than that of the West. This study makes a significant contribution to understanding the military and social situation of the late Roman Empire.

An examination of how ancient and medieval military thought shaped the practice of war, covering strategy, tactics, and organization.

The Roman Army: A Social and Institutional History examines the Roman military from the perspective of its soldiers, detailing its organization, daily life, and lasting adaptability over nearly a millennium.