Arrian’s Array

Flavius Arrianus (c. A.D. 96-c. 170) is a leading witness to the fact that though, on the eve of the Roman collapse in the West, Roman armies in, for instance, the Diocese of the Gauls and the isle of Britain, consisted of at least two parts cavalry to one of infantry, this process of turning to the horse was already far advanced in the eastern half of the Empire in the second century of our era.

This change had been forced on the Roman military establishment, whose traditions of prestige derived from the well-equipped and superbly drilled legions which were essentially infantry brigades supported by light-armed troops, not all of them mounted, and containing within their ranks sappers adept at fortification, siege-work and river-crossing by bridge or boat, artillerymen serving balistas and catapults, and craftsmen capable of building and equipping not only permanent barracks but municipal buildings good enough at least for colonial purposes.