Ardaburius drew off on his approach, burned his siege artillery, and retired from before the place.

Nisibis was preserved; but soon afterwards a disaster is said to have befallen the Arabs, who, believing themselves about to be attacked by the Roman force, were seized with a sudden panic, and, rushing in headlong flight to the Euphrates (!) threw themselves into its waters, encumbered with their clothes and arms, and there perished to the number of a hundred thousand.
The remaining circumstances of the war are not related by our authorities in chronological sequence.

But as it is certain that the war lasted only two years, and as the events above narrated certainly belong to the earlier portion of it, and seem sufficient for one campaign, we may perhaps be justified in assigning to the second year, A.D.421, the other details recorded--viz., the siege of Theodosiopolis, the combat between Areobindus and Ardazanes, the second victory of Ardaburius, and the destruction of the remnant of the Arabs by Vitianus.
Theodosiopolis was a city built by the reigning emperor, Theodosius II., in the Roman portion of Armenia, near the sources of the Euphrates.
It was defended by strong walls, lofty towers, and a deep ditch.

Hidden channels conducted an unfailing supply of water into the heart of the place, and the public granaries were large and generally well stocked with provisions.

This town, recently built for the defence of the Roman Armenia, was (it would seem) attacked in A.D.421 by Varahran in person.
He besieged it for above thirty days, and employed against it all the means of capture which were known to the military art of the period.
But the defence was ably conducted by the bishop of the city, a certain Eunomius, who was resolved that, if he could prevent it, an infidel and persecuting monarch should never lord it over his see.