Camps and forts of units and formations of the Roman army

A previously outlined paradigm for laying out Roman camps was used to fit particular auxiliary units to certain small camps. A spreadsheet for estimating the numbers of cavalry and infantry within camps is described and illustrated by reference to the putative camps of a two-legion army group, a one-legion group and two subdivisions of a legionary army group. The same paradigm with different constants applied to forts and legionary fortresses with, on average, the intervallum 1/16th of the sq. root of the area it enclosed in the fort and 1/32nd in the fortress. In the forts of both auxiliary units and legionary vexillations, each notional cohort (480 infantry or 240 cavalry) was almost certainly intended to have eight actus quadrati (a.q.) within the intervallum. This allowed the forts later to contain larger auxiliary units. Dividing a fort's acreage by 3.25 indicates the number of notional cohorts for which it was probably first made. The vexillation fort at Longthorpe was probably intended for half a legion and the reduced fort built for two auxiliary units. In legionary fortresses each notional cohort had 12 a.q. The paradigm applied to the Heidenheim fort suggested that an ala milliaria comprised 24 turmae of 42 men. The fortress at York was probably first built as a legionary fort.