The Ecclesiastical History of Sozomen

Under the government of Constantine the churches flourished and increased in numbers daily, since they were honored by the good deeds of a benevolent and well-disposed emperor, and otherwise God preserved them from the persecutions and harassments which they had previously encountered. When the churches were suffering from persecution in other parts of the world, Constantius alone, the father of Constantine, accorded the Christians the right of worshiping God without fear. I know of an extraordinary thing done by him, which is worthy of being recorded. He wished to test the fidelity of certain Christians, excellent and good men, who were attached to his palaces. He called them all together, and told them that if they would sacrifice to idols as well as serve God, they should remain in his service and retain their appointments; but that if they refused compliance with his wishes, they should be sent from the palaces, and should scarcely escape his vengeance. When difference of judgment had divided them into two parties, separating those who consented to abandon their religion from those who preferred the honor of God to their present welfare, the emperor determined upon retaining those who had adhered to their faith as his friends and counselors; but he turned away from the others, whom he regarded as unmanly and impostors, and sent them from his presence, judging that they who had so readily betrayed their God could never be true to their king. Hence it is probable that while Constantius was alive, it did not seem contrary to the laws for the inhabitants of the countries beyond Italy to profess Christianity, that is to say, in Gaul, in Britain, or in the region of the Pyrenean mountains as far as the Western Ocean. When Constantine succeeded to the same government, the affairs of the churches became still more brilliant; for when Maxentius, the son of Herculius, was slain, his share also devolved upon Constantine; and the nations who dwelt by the river Tiber and the Eridanus, which the natives call Padus, those who dwelt by the Aquilis, whither, it is said, the Argo was dragged, and the inhabitants of the coasts of the Tyrrhenian sea were permitted the exercise of their religion without molestation.

When the Argonauts fled from Æetes, they returned homewards by a different route, crossed the sea of Scythia, sailed through some of the rivers there, and so gained the shores of Italy, where they passed the winter and built a city, which they called Emona. The following summer, with the assistance of the people of the country, they dragged the Argo, by means of machinery, the distance of four hundred stadia, and so reached the Aquilis, a river which falls into the Eridanus: the Eridanus itself falls into the Italian sea.

After the battle of Cibalis the Dardanians and the Macedonians, the inhabitants of the banks of the Ister, of Hellas, and the whole nation of Illyria, became subject to Constantine.