When did the Roman Army decline?

[Renatus]

The Clarke translation of Vegetius was being used by the US military even up to 1946 as I have a copy of the US Military School publication of Vegetius from 1946 that was issued to officer candidates in the US army.

This is the abridgement of the first three books of Lt. Clarke's translation, first published by Maj. (later Brig. Gen.) T. R. Phillips in 1940 as part of a collection of military classics under the title Roots of Strategy. The collection comprised Sun Tzu's The Art of War, Vegetius, Maurice de Saxe's My Reveries upon the Art of War, Frederick the Great's Military Instructions for the Generals and Napoleon's Military Maxims. In his Synopsis of Contents, Phillips says of these, " . . . all are an indispensible part of an officer's military education and the foundation of a military library." He concludes his Editor's Foreward by saying, "It is hoped that this volume, containing the most influential military works of the past, may increase appreciation of the effect of military ideas on the course of history and the fate of nations, and assist in demonstrating the historical importance of military thought."

It seems, therefore, that Phillips was approaching these works as military history, rather than for their practical value, although no doubt much valuable practical advice could be found in them. On the other hand, it was for its practical value that Vegetius' work was prized in the Middle Ages. The commanders who used him did not care a jot what period of Roman history any part of his work might relate to or whether his interpretations were accurate. It was what he said about the practicalities of maintaining an army in the field that they were interested in and that was timeless.

Vegetius' first book, which he submitted to his Emperor unsolicited, is something of a polemic aimed at improving the recruitment and training of the soldiery. To some extent, therefore, there is an element of hyperbole in it. His subsequent books, which he prepared on the instructions of the Emperor, are somewhat different. In Book 2, he attempts to reconstruct the ancient legion and gets in a muddle in doing so. It is highly unlikely that anyone had written a history of the army, describing its development over time. Vegetius was, therefore, faced with differing descriptions, each relating to the army as it was at the time that the particular source was written. I have argued that Vegetius believed the legion to have remained largely unchanged since its inception, with the result that, in trying to combine the differing descriptions that he had, each relating to a different period, he produced a legion that had never existed. To his credit, he realised that his construction did not really hold together and admitted as much, leaving it to his readers to absorb the information that he had given and to work out the answers for themselves. His remaining books are much more successful and it is in these that is found the practical advice that made him so influential. Apart from Book 2, his Epitoma is, to all intents and purposes, a handbook on how to recruit, train and use an army. The mistake that his critics make is to believe that he was writing a military history; he was not.