Ammianus Marcellinus, a Roman army officer, provided a vivid description of the siege in his work (
Res Gestae). Ammianus served on the staff of
Ursicinus, the
Magister Equitum (master of horse) of the East, during the events of the siege.
Persian When
Shapur II took control of the Sasanian Empire, he sought to regain old territories previously lost to the Roman Empire. After
crushing the Arabs in the south, Shapur II had to fight for a decade against invaders called the
Xionites. He was successful in his efforts, asserting his dominance over the invaders and securing his eastern borders. The
Xionites were forced to conclude a peace, and their king,
Grumbates, accompanied Shapur II in the war against the Romans. In 358 the Romans had failed to dissuade Shapur from attacking
Mesopotamia, so the next year Shapur decided to invade. Shapur besieged Amida in 359.
Roman Emperor
Constantius II had increasingly been doubting the loyalty of General Ursicinus. As a result, he did not give him command of the Roman forces in the East, and instead gave it to Sabinianus. Ursicinus served as Magister Equitum (Master of Horse) while Sabinianus held the rank of
Magister Peditum (Master of Foot) of the East. As events unfolded, Ursicinus became the 'de facto' commanding general of the
Limitanei armies of Mesopotamia and Osrhoene, while Sabinianus continued as commander of
Comitatus (the Field Army) of the East. As news of the Persian invasion spread, the civilian population of the region began to panic: Several
Roman legions gathered at Amida. These included:
Legio XXX Ulpia Victrix, Magnentius, Decentius, Superventores, Praeventores and a detachment of
Legio X Fretensis. The garrison of Amida itself consisted of
Legio V Parthica supported by an unidentified cavalry regiment. Ursicinus probably planned to use Amida as a base of operations against the Persian invasion. ==Preliminaries of the siege==