THE DIVISIONS OF THE ARMY
A text by the Latin historian Tacitus, who in his Annalsl describes the forces Tiberius had at his disposal in AD 23, is a good demonstration of the complexity of the Roman army:
To begin with the capital of the Empire: the ten thousand men who made up what is called 'the garrison of Rome' were not stationed at first in the very heart of the city. In particular, most of the praetorians were distributed by Augustus throughout the cities of Latium until the inhabitants became accustomed to seeing armed men in the streets, a situation contrary to the political and religious traditions of the Republic. Afterwards the troops were regrouped, mainly in the outlying districts, and true barracks were finally created between the Viminal, the Caelian and the Esquiline hills (pI. III, 4).