Ammianus Marcellinus Res Gestae 19.11.2

[2] The emperor, believing that these outrages would soon be pushed to greater heights if the matter were postponed, assembled from every quarter a great number of soldiers most eager for war and took the field before spring had yet fully come; he was the more eager for action from two considerations: first, because an army glutted with the rich booty of the past summer, by the hope of similar booty would be confidently encouraged to achieve successful enterprises, and because under Anatolius, ¹ who at that time was prefect of Illyricum, all necessary supplies had been brought together even ahead of time and were still coming in without trouble to anyone.