ABSTRACT
We begin with a definition of what is meant by the regular Roman army. I mean the regular professional force with its unique record of victory going back to Augustus and Marius and beyond. This was possibly the most successful military organization of all history and it continued to perform up to expectations at least up to 378 when Valens was defeated at Adrianople. That was the end of invincibility, but not the end of the army. Around 400 somebody compiled the Notitia Dignitatum, a list of all the units in the armies of both halves of the empire. It was a formidable force which Jones (1964, 418-60) estimated at 645,000. Jones’s estimate is certainly much too high. He did not take into account the high likelihood that unit strength in the late Roman army was very much smaller than in the early Empire. This is quite apart from the probability recognized by Jones that the Notitia represents paper establishments likely to have been much larger than the forces actually available (Liebeschuetz 1990a, 41; Duncan-Jones 1990, 105-17).
