Similar letters were sent to Chosroes, King of Persia, and to Heraclius, the Christian Emperor at Constantinople. The former tore the letter in pieces contemptuously, for at that time his kingdom extended over the greater part of Asia; Jerusalem, once the pride of the Eastern Empire, had fallen into his grasp; while his armies were besieging Constantinople itself. A letter that he himself penned to the Christian Emperor shows his overweening pride, and the depths into which Byzantium had fallen in the public regard:
‘Chosroes, Greatest of Gods, and Master of the whole earth, to Heraclius, his vile and insensate slave. Why do you still refuse to submit to our rule and call yourself a king? Have I not destroyed the Greeks? You say that you trust in your God. Why has he not delivered out of my hand Caesarea, Jerusalem, Alexandria? and shall I not also destroy Constantinople? But I will pardon your faults if you will submit to me, and come hither with your wife and children, and I will give you lands, vineyards, and olive groves, and look upon you with a kindly aspect. Do not deceive yourself with vain hope in that Christ, who was not even able to save himself from the Jews, who killed him by nailing him to a cross. Even if you take refuge in the depths of the sea I shall stretch out my hand and take you, so that you shall see me whether you will or no.’
Christendom was fortunate in Heraclius. Instead of contemplating either despair or surrender, he called upon the Church to summon all Christians to his aid, and by means of the gold and silver plate presented to him as a war loan by the bishops and clergy, and in command of a large army of volunteers, he beat back the Persians from the very gates of his capital. Not content with a policy of defence, he next invaded Asia, and at the battle of Nineveh utterly destroyed the hosts of Chosroes. The fallen King, deposed by his subjects, was forced to take refuge in the mountains, and later was thrown into a dungeon where he died of cold and starvation.
Had the reign of Heraclius ended at this date, it would be remembered as a glorious era in the history of Constantinople; but unfortunately for his fame another foe was to make more lasting inroads on his Empire, already weakened by the Persian occupation.