The Roman Invasion of A.D. 43

Modern attempts to investigate the sources of his History2 have raised doubts about the reliability of certain details: in the chapters which concern us the description of the river-battle as lasting into a second day and even the division of the army into three parts before sailing3 have been held to be mere literary topoi. But these suggestions are by no means certain, for each passage is well suited to its context. With one emendation of the text, noted below, we see no certain justification in rejecting any part of Dio's account of the campaign. However, even if the passages concerned could be established as topoi, their rejection would make virtually no difference to an understanding of the campaign, for, as we shall show, the three divisions are irrelevant to the development of the advance while the reduction of the battle-span from one and a half days to one does not detract from the difficulties of the river crossing or from the decisiveness of victory. A first principle of successful campaigning in war, once active hostilities have begun, is to concentrate all the forces that you can muster and make for your enemy's source of power as speedily as possible, there to deal him the decisive blow which in turn will place your secondary objectives within your grasp. This principle can be identified in the campaigns of Alexander, Caesar or Trajan, as also in those of more recent commanders such as Marlborough, Nelson or Napoleon. It was succinctly stated by the nineteenth-century US General Forrest: 'Get thar fastest with the most men'; but Forrest had been anticipated by Xenophon,4 who wrote, 'If you attack expecting to prevail, do it in full strength, because a surplus of victory never caused any conqueror one pang of remorse'." Several reasons based in high policy have been adduced in modern times for the decision to invade Britain, including Claudius' own need to be seen as a vir militaris; but for the army in A.D. 43 there were two immediate objectives: (1) the restoration of the southern kingdom of the aged Verica, a Roman ally who had fled to Claudius, and (2) the defeat of the Catuvellaunian princes whose pressure had caused his flight. The first objective could not be finally and securely met without achievement of the second, and was accordingly a secondary objective. The southern kingdom had recently been overrun by Catuvellaunian forces and a Roman landing near Chichester could anticipate strong resistance, even if the native Atrebatic population itself was friendly. Moreover, the principal centre of the Atrebates from which Verica had been driven first in the A.D. 20s or 30s6 was Calleva (Silchester), some 40 miles inland. We learn two valuable facts from Dio's account:7 (1) that the embarkation of Plautius' forces was delayed till late in the season by a mutiny and the need to consult with Rome; and (2) that