The most important limitation Ammianus displayed as a military historian was that he barely mentioned chronology or topography. This is one of Ammianus more serious weaknesses that can not always be accounted for by artistic motives. Ammianus had another important weakness. He described battles in the field in much less detail than he does sieges. There is a good explanation for this to be found in the fact that a siege is always more static than a battle. Maybe another explanation could be that Ammianus had a keen interest in (exceptional) war-machines used in the sieges. All the above arguments go a long way in explaining Ammianus thorough knowledge of warfare by his own career and his curiosity. Nevertheless, one has to keep in mind the historians weaknesses.
Ammianus actual career is not Crump's focus. He investigates Ammianus remark that he wrote his Res Gestae as a soldier and a Greek (31.16.9). This remark should be placed within the context of classical thinkers who judged this combination highly desirable. As a Greek, Ammianus possessed the formal education that came with a standard (Greek) rhetorical curriculum. As a soldier he would have had the practical experiences needed to write military history.Ammianus never lost sight of the human element, the res gestae in his narrative. This is not only because the audience wanted a story to pivot around these occurrences, but also because Ammianus was an old soldier, aware that ancient warfare was about the decisive deeds of men. According to Crump, as a story of human deeds, Ammianus work is rarely incorrect, usually competent, and sometimes comparable to the best examples of classical historiography [Crump 131]. The artistic paraphernalia do not seem to destroy the accuracy of the Res Gestae on military subjects, but only interrupt the story. In the digression about artillery, Ammianus gives technical details to his readers about fourth-century siege warfare that would otherwise interrupt his narrative. This goes beyond the original purpose of a digression: showing the writers study and erudition. All in all Ammianus can be seen as a qualified military historian in his own historiographical tradition.
- Austin, N.J.E., Ammianus on Warfare. An Investigation into Ammianus Military Knowledge, Collection Latomus 165, Brussels 1979