Throughout the period of the late Republic and Principate Rome was the dominant military force in the Mediterranean. With the exception of a few noted and quite spectacular disasters it was not until the latter part of the period that Roman military superiority came to be challenged regularly. There is a wealth of archaeological and epigraphic evidence relating to the Roman imperial army, its arms and equipment, its organization and rank structure, its fortifications, its religious beliefs and practices and so on. The majority of studies of the Roman army, whether for reasons of evidence or because of the prevailing social and political atmosphere, have tended to concentrate on these issues rather than on the army as a fighting force. It is only in the last decade or so that this imbalance has begun to be redressed.

When it comes to actual fighting the evidence (except for Caesar’s campaigns) is far less extensive. Narratives of campaigns by historians of the imperial period often lack the detail of earlier writers such as Polybius and Livy, and though Tacitus, the ‘most unmilitary of historians’, might have complained about the lack of wars of conquest and battles to describe in his histories, when he has the opportunity with the Parthian campaigns under Nero, he deals with them in an almost cursory fashion (Ann. 4.33). Events in Rome were much more interesting. The virtus of the battlefield surrenders to the vice of the imperial bedchamber.