The citizens of Nisibis were animated by the exhortations of their bishop, inured to arms by the presence of danger, and convinced of the intentions of Sapor to plant a Persian colony in their room, and to lead them away into distant and barbarous captivity.

The event of the two former sieges elated their confidence, and exasperated the haughty spirit of the Great King, who advanced a third time towards Nisibis, at the head of the united forces of Persia and India.

The ordinary machines, invented to batter or undermine the walls, were rendered ineffectual by the superior skill of the Romans; and many days had vainly elapsed, when Sapor embraced a resolution worthy of an eastern monarch, who believed that the elements themselves were subject to his power.

At the stated season of the melting of the snows in Armenia, the River Mygdonius, which divides the plain and the city of Nisibis, forms, like the Nile, an inundation over the adjacent country.

By the labor of the Persians, the course of the river was stopped below the town, and the waters were confined on every side by solid mounds of earth.