Limitanei and Comitatenses: Military Failure at the End of Roman Britain? By Rob Collins and David Breeze * ABSTRACT Presumptions of military failure at the end of Roman Britain are a recurring feature of many modern accounts.While there is some support in ancient sources for the withdrawal of soldiers from Britain in the late fourth and early ffth centuries, archaeological evidence also suggests activity at many Roman military sites in the ffth century. A review of the military history as suggested by Roman sources, as well as a consideration of the organisation of both the late Roman military and fourth-century Britain, promotes a regional approach to interpreting military archaeology and history in the fnal years of Roman Britain, with particular emphasis on the distinct military commands in the diocese. There is no single cause or simple explanation for the end of Roman Britain, but the presumption of military failure is a recurring feature of many accounts that warrants a reconsideration of the fate of the soldiers defending Britain in the early ffth century. The underlying assumptions for military failure have varied, from the straightforward total withdrawal of soldiers, to the collapse of the infrastructure that supplied any remaining soldiers. A model was proposed suggesting that the armies of the diocese of Britain were too small through the fourth century to have sufered many, if any, troop withdrawals (James 1984), but the size of the estimated force in the model may have been too conservative, and there does seem to be evidence of some withdrawal of soldiers in the fnal decades of Roman Britain. Excavations in the northern frontier over the past 30 years, however, have demonstrated continued activity at a number of late Roman military installations into the ffth century, and in some cases later. A model arguing for the transformation of late Roman military units into sub- Roman warbands has been proposed (Casey 1993; Wilmott 1997; Collins 2012), but thus far the model has only been applied to evidence from the northern frontier. The military situation at the end of Roman Britain for the entire diocese has been considered in focused discussions of ‘the end’ (e.g. Dark 2000; Esmonde Cleary 1989; Faulkner 2004) or in more general accounts of Roman Britain (e.g. Millett 1990; Mattingly 2006). In such treatments, the military garrison of the island has been portrayed in a generic fashion as an imperial institution at a broader geographic scale, as it relates to other structural aspects of Roman imperial government. However, an examination of the late Roman military commands of Britannia reveals likely geographic patterning, further reinforcing the plethora of evidence for the signifcance of regionality in Roman and post-Roman Britain. This paper provides a brief overview of the structure of the late Roman army and its disposition in Britain, followed by a consideration of reasons for military failure or continuity. The archaeological evidence is reviewed geographically to test the notion of continued military presence c. a.d. 400. THE FOURTH-CENTURY ROMAN ARMY The late Roman army was structurally and operationally diferent to that of the early Roman Empire. This evolution occurred throughout the third century, but changes were formalised under Diocletian, Constantine and subsequent emperors, and there is no evidence that the ‘fghting quality’ of the late Roman army diminished. A number of general studies provide a * University of Newcastle upon Tyne; robert.collins@newcastle.co.uk; davidbreeze@hotmail.co.uk