The ravages of the pestilence having ceased, Chosroes, in the following year (A.D. 544), again marched westward in person, and laid siege to the city of Edessa.  It would seem that he had now resolved not to be content with plundering raids, but to attempt at any rate the permanent conquest of some portion of the Roman territory.  Edessa and Daras were the two towns on which the Roman possession of Western Mesopotamia at this time mainly depended.  As the passing of Nisibis, in A.D. 363, from Roman into Persian hands, had given to Persia a secure hold on the eastern portion of the country between the rivers, so the occupation of Edessa and Daras could it have been effected, would have carried with it dominion over the more western regions.  The Roman frontier would in this way have been thrown back to the Euphrates.  Chosroes must be understood as aiming at this grand result in the siege which he so pertinaciously pressed, and which Edessa so gallantly resisted, during the summer of A.D. 544.  The elaborate account which Procopius gives of the siege may be due to a sense of its importance.  Chosroes tried, not force only, but every art known to the engineering science of the period; he repeated his assaults day after day; he allowed the defenders no repose; yet he was compelled at last to own himself baffled by the valor of the small Roman garrison and the spirit of the native inhabitants, to burn his works, and to return home.  The five hundred pounds of gold which he extorted at last from Martinus, the commandant of the place, may have been a salve to his wounded pride; but it was a poor set-off against the loss of men, of stores, and of prestige, which he had incurred by his enterprise.

It was, perhaps, his repulse from the walls of Edessa that induced Chosroes, in A.D. 545, seriously to entertain the proposals for an arrangement which were made to him by the ambassadors of Justinian.  Throughout the war their had been continual negotiations; but hitherto the Persian king had trifled with his antagonist, and had amused himself with discussing terms of accommodation without any serious purpose.  Now at last, after five years of incessant hostilities, in which he had gained much glory but little profit, he seems to have desired a breathing-space.  Justinian’s envoys visited him at Ctesiphon, and set forth their master’s desire to conclude a regular peace.  Chosroes professed to think that the way for a final arrangement would be best prepared by the conclusion, in the first instance, of a truce.  He proposed, in lieu of a peace, a cessation of hostilities for five years, during the course of which the causes of quarrel between the two nations might be considered, and a good understanding established.  It shows the weakness of the Empire, that Justinian not only accepted this proposal, but was content to pay for the boon granted him.  Chosroes received as the price of the five years truce the services of a Greek physician and two thousand pounds of gold.