Summary

The beginnings of Roman military camps are obscure. Although considerably more recent written sources mention camps being built during the battles with neighbouring towns and tribes as early as the Roman Regal Period, archaeological remains of such installations have only been found since the 2nd century bce, especially on the Iberian Peninsula. Beginning with the early Imperial Period, our knowledge of castra—in various regions of the empire, but also beyond the imperial borders—is considerably greater than during the time of the Republic.

The few and scattered written sources deal only marginally with the different functions of the camps. With the help of large-scale excavations and geophysical and aerial photo surveys, it is possible to make a differentiation and functional determination among them. Despite standardisation, no two camps are alike: the well-known rectangular plan with rounded camp corners is only one of the known forms of camp design and organisation (castrametatio). In Late Antiquity, Roman camps, together with the Roman army system in general, were subject to fundamental change. Adaptation to threats from external enemies, but also from recurring civil wars within the empire, also affected the design, size, and internal layout of late Roman camps: the standardisation of the early and middle Imperial Period no longer plays much of a role, the areas to be defended are clearly reduced, natural protection is taken into account in new construction, and the camp defences are considerably strengthened. These characteristics of late Imperial camps were adopted by the early Eastern Roman Empire.