The war now approached its termination; for the last hope of the Persians had failed; and Heraclius, with his mind set at rest as regarded his capital, was free to strike at any part of Persia that he pleased, and, having the prestige of victory and the assistance of the Khazars, was likely to carry all before him.  It is not clear how he employed himself during the spring and summer of A.D. 627; but in the September of that year he started from Lazica with a large Roman army and a contingent of 40,000 Khazar horse, resolved to surprise his adversary by a winter campaign, and hoping to take him at a disadvantage.  Passing rapidly through Armenia and Azerbijan without meeting an enemy that dared to dispute his advance, suffering no loss except from the guerilla warfare of some bold spirits among the mountaineers of those regions, he resolved, notwithstanding the defection of the Khazars, who declined to accompany him further south than Azerbijan, that he would cross the Zagros mountains into Assyria, and make a dash at the royal cities of the Mesopotamian region, thus retaliating upon Chosroes for the Avar attack upon Constantinople of the preceding year, undertaken at his instigation.  Chosroes himself had for the last twenty-four years fixed his court at Dastagherd in the plain country, about seventy miles to the north of Ctesiphon.  It seemed to Heraclius that this position might perhaps be reached, and an effective blow struck against the Persian power.  He hastened, therefore, to cross the mountains; and the 9th of October saw him at Chnaethas, in the low country, not far from Arbela, where he refreshed his army by a week’s rest.  He might now easily have advanced along the great post-road which connected Arbela with Dastagherd and Ctesiphon; but he had probably by this time received information of the movements of the Persians, and was aware that by so doing he would place himself between two fires, and run the chance of being intercepted in his retreat.  For Chosroes, having collected a large force, had sent it, under Ehazates, a new general, into Azerbijan; and this force, having reached Canzaca, found itself in the rear of Heraclius, between him and Lazica.  Heraclius appears not to have thought it safe to leave this enemy behind him, and therefore he idled away above a month in the Zab region, waiting for Ehazates to make his appearance.  That general had strict orders from the Great King to fight the Romans wherever he found them, whatever might be the consequence; and he therefore followed, as quickly as he could, upon Heraclius’s footsteps, and early in December came up with him in the neighborhood of Nineveh.  Both parties were anxious for an immediate engagement, Rhazates to carry out his master’s orders, Heraclius because he had heard that his adversary would soon receive a reinforcement.  The battle took place on the 12th of December, in the open plain to the north of Nineveh.  It was contested from early dawn to the eleventh hour of the day, and was finally