Zosimus, New History 6.13



[6.13.1] Such was the state of Italy, while Constantine gave a diadem to his son Constans, and from a caesar raised him to an emperor; after having deprived Apollinarius of his office, and appointed another person prefect of the court in his room. In the meantime Alaric proceeded to Ravenna to confirm the peace with Honorius; but fortune invented another obstacle beyond all expectation, and as it were pointed out what should befal the commonwealth. 

[6.13.2] For while Sarus was stationed with a few barbarians in Picenum, and joined neither with the emperor nor with Alaric, Athaulf, who had an animosity against him on the ground of some former difference, came with his whole army to the place where Sarus happened to be. As soon as Sarus perceived him approaching, finding himself not able to centend with him, as he had only three hundred men, he resolved to fly to Honorius, and assist him in the war against Alaric.