We are told that on one occasion Prince Hormisdas narrowly escaped falling into the surena's hands.

On another, the Persian force, having allowed the Roman vanguard to proceed unmolested, suddenly showed itself on the southern bank of one of the great canals connecting the Euphrates with the Tigris, and forbade the passage of Julian's main army.

It was only after a day and a night's delay that the emperor, by detaching troops under Victor to make a long circuit, cross the canal far to the east, recall Lucilianus with the vanguard, and then attack the surena's troops in the rear, was able to overcome the resistance in his front, and carry his army across the cutting.
Having in this way effected the passage, Julian continued his march along the Euphrates, and in a short time came to the city of Perisabor (Mruz Shapur), the most important that he had yet reached, and reckoned not much inferior to Otesiphon.

As the inhabitants steadily refused all accommodation, and insulted Hormisdas, who was sent to treat with them, by the reproach that he was a deserter and a traitor, the emperor determined to form the siege of the place and see if he could not compel it to a surrender.

Situated between the Euphrates and one of the numerous canals derived from it, and further protected by a trench drawn across from the canal to the river, Perisabor occupied a sort of island, while at the same time it was completely surrounded with a double wall.
The citadel, which lay towards the north, and overhung the Euphrates, was especially strong; and the garrison was brave, numerous, and full of confidence.