The Ecclesiastical History of Socrates Scholasticus

Now the emperor of the Romans dwelling in Constantinople being fully aware that God had plainly given him the victory was so benevolent that although those under him had been successful in war nevertheless he desired to make peace; and to that end he dispatched Helion, a man in whom he placed the greatest confidence, with a commission to enter into a pacific treaty with the Persians. Helion having arrived in Mesopotamia, at the place where the Romans for their own security had formed a trench, sent before him as his deputy Maximin an eloquent man who was the associate of Ardaburius the commander-in-chief of the army, to make preliminary arrangements concerning the terms of peace. Maximin on coming into the presence of the Persian king, said he had been sent to him on this matter, not by the Roman emperor, but by his generals; for he said this war was not even known to the emperor, and if known would be considered insignificant by him. And as the sovereign of Persia had gladly decided to receive the embassy,—for his troops were suffering from want of provisions,—there came to him that corps among them which is distinguished by the name of ‘the Immortals.’ This is a body of brave men numbering about ten thousand—and counselled the king not to listen to any overtures for peace, until they should have made an attack upon the Romans, who, they said, were now become extremely incautious. The king approving their advice, ordered the ambassador to be imprisoned and a guard set over him, and permitted the Immortals to put their design upon the Romans into execution. They therefore, on arriving at the place appointed, divided themselves into two bands, with a view to surround some portion of the Roman army. The Romans observing but one body of Persians approaching them, prepared themselves to receive it, not having seen the other division, in consequence of their suddenly rushing forth to battle. But just as the engagement was about to commence, Divine Providence so ordered it, that another division of the Roman army under Procopius a general emerged from behind a certain hill and perceiving their comrades in danger, attacked the Persians in the rear. Thus were they, who but a little before had surrounded the Romans, themselves encompassed. Having utterly destroyed these in a short time, the Romans turned upon those who broke forth from their ambuscade and in like manner slew every one of them with darts. In this way those who by the Persians were termed ‘the Immortals’ were all of them shown to be mortal, Christ having executed this vengeance upon the Persians because they had shed the blood of so many of his pious worshippers. The king of the Persians on being informed of the disaster, pretended to be ignorant of what had taken place, and ordered the embassy to be admitted, he thus addressing the ambassador: ‘I agree to the peace, not as yielding to the Romans, but to gratify you, whom I have found to be the most prudent of all the Romans.’ Thus was that war concluded which had been undertaken on account of the suffering Christians in Persia, under the consulate of the two Augusti, being the thirteenth of Honorius, and the tenth of Theodosius, in the fourth year of the 300th Olympiad: and with it terminated the persecution which had been excited in Persia against the Christians.