ABSTRACT
Chapters 4.1-6.7 of Book 18 of the Res Gestae have been aptly called the ‘preface’ to Ammianus’ account of the Persian invasion of 359.2 With these chapters Ammianus sets the scene for the actual invasion, which reaches its climax in the siege and destruction of Amida. In short, the events are as follows. Shapur, the king of the Persians, is preparing for a major campaign against the Romans (18.4). Antoninus, a Roman, defects to the Persians with detailed intelligence on the Roman defences in the East and encourages Shapur to attack the Roman provinces (18.5). Ursicinus, serving as magister equitum in the East, receives an order to yield his position to Sabinianus and return to the court in Sirmium. He is to succeed Barbatio, the magister peditum at court, who has been executed for treason. However, on his way to Sirmium Ursicinus receives new orders, instructing him to return and to conduct the defence of the eastern border, yet without being restored to his former rank (18.6).
