The object of Chosroes in thus changing his return line of march was to continue in Roman Mesopotamia the course which he had adopted in Syria since the conclusion of the truce--i.e.to increase his spoil by making each important city ransom itself.

Edessa, Constantina, and Daras were successively visited, and purchased their safety by a contribution.

According to Procopius, the proceedings before Daras were exceptional.

Although Chosroes, before he quitted Edossa, had received a communication from Justinian accepting the terms arranged with the Roman envoys at Antioch, yet, when he reached Daras, he at once resolved upon its siege.

The city was defended by two walls, an outer one of moderate strength, and an inner one sixty feet high, with towers at intervals, whose height was a hundred feet.