During the Middle Empire period (AD 180-284) the Roman army had to face the terrible 'Third Century Crisis', wherein a combination of socio-economic problems and new external threats threatened the Empire with complete collapse. Several provinces became temporarily independent from the central government of Rome, while others were frequently raided by foreign invaders. The Roman army had to fight with all its resources in order to reconquer a good portion of the Empire and preserve its unity. The Romans were forced to modernize and reform their forces to face the new challenges posed by a multitude of warlike enemies, such as the Persians in the Middle East or the Germanic Peoples in Central Europe. The previous military system based on the power of the legions' heavy infantry was completely revised, with the introduction of new organizational patterns. Cavalry became much more important than before, together with light troops specialized in skirmishing. The personal equipment of the Roman soldiers changed in a very significant way, with the introduction of new weapons that permitted the development of innovative tactics. Gabriele Esposito follows this evolution of Roman forces from the death of Marcus Aurelius to the rise of Diocletian, reconstructing the major military campaigns and explaining how the Roman military forces were transformed.

All the major troop types are covered, with details on the organization and equipment of each contingent. The book is lavishly illustrated throughout with excellent colour photos of reconstructed costume and equipment in use.