Roman preparation for conflict with Persia began in 335, initiated by the militarily capable Constantius, the son of the pious emperor Constantine the Great. A year later, the Sasanians invaded Mesopotamia and captured the city of Amida, deep in Roman territory. The Roman response was swift, and they clashed with the Sasanians at Narasara (present-day location unknown), killed the Persian general Narses, recaptured Amida, and improved its fortifications. This would prove invaluable when it was besieged again in 359. The death of Constantine the Great in 337 gave the Sasanian king Shapur II an opportunity to invade Mesopotamia - according to Theodoret of Cyrrhus in his Historia Religiosa, Shapur "despised the sons of Constantine as being less capable than their father" (1.1 1-12). Shapur's army reached the city of Nisibis in the same year, located on present-day Turkey's border with Syria.
Sieges and savarans
Once Nisibis was surrounded, Shapur II demanded its surrender, which was refused by its defenders. It was now besieged, with assaults on the city supported by archers on siege towers, and its walls undermined by engineers. After these attempts failed, Shapur II dammed the Mygdonius River, and after enough of it had built up, he unleashed it against a section of the walls, which was destroyed by the deluge. The soldiers and citizens 2.26). The defenders, filled with religious fervour, worked tirelessly to rebuild the walls. By the morning of the following day, they had succeeded enough to prevent the Sasanians from entering the city. When this attempt to capture the city failed, Shapur II raised the siege, which had lasted 70 days.
