But this valuable support to his cause was no free gift of a generous friend; on the contrary, it had to be purchased by great sacrifices.  Chosroes had perhaps at first hoped that aid would be given him gratuitously, and had even regarded the cession of a single city as one that he might avoid making.  But he learnt by degrees that nothing was to be got from Rome without paying for it; and it was only by ceding Persarmenia and Eastern Mesopotamia, with its strong towns of Martyropolis and Daras, that he obtained the men and money that were requisite.

Meanwhile Bahram, having occupied Ctesiphon, had proclaimed himself king, and sent out messengers on all sides to acquaint the provinces with the change of rulers.  The news was received without enthusiasm, but with a general acquiescence; and, had Maurice rejected the application of Chosroes, it is probable that the usurper might have enjoyed a long and quiet reign.  As soon, however, as it came to be known that the Greek emperor had espoused, the cause of his rival, Bahram found himself in difficulties:  conspiracy arose in his own court, and had to be suppressed by executions; murmurs were heard in some of the more distant provinces; Armenia openly revolted and declared for Chosroes; and it soon appeared that in places the fidelity of the Persian troops was doubtful.  This was especially the case in Mesopotamia, which would have to bear the brunt of the attack when the Romans advanced.  Bahram therefore thought it necessary, though it was now the depth of winter, to strengthen his hold on the wavering province, and sent out two detachments, under commanders upon whom he could rely, to occupy respectively Anatho and Nisibis, the two strongholds of greatest importance in the suspected region.  Miraduris succeeded in entering and occupying Anatho.  Zadesprates was less fortunate; before he reached the neighborhood of Nisibis, the garrison which held that place had deserted the cause of the usurper and given in its adhesion to Chosroes; and, when he approached to reconnoitre, he was made the victim of a stratagem and killed by an officer named Rosas.  Miraduris did not long survive him; the troops which he had introduced into Anatho caught the contagion of revolt, rose up against him, slew him, and sent his head to Chosroes.

The spring was now approaching, and the time for military operations on a grand scale drew near.  Chosroes, besides his supporters in Mesopotamia, Roman and Persian, had a second army in Azerbijan, raised by his uncles Bindoes and Bostam, which was strengthened by an Armenian contingent.  The plan of campaign involved the co-operation of these two forces.  With this object Chosroes proceeded early in the spring, from Hierapolis to Constantina, from Constantina to Daras, and thence by way of Ammodion to the Tigris, across which he sent a detachment, probably in the neighborhood of Mosul.  This force fell in with Bryzacius, who commanded in these parts for Bahram, and surprising