Nicene and Post-Nicene Fathers, Ser. II, Vol I:
The Life of Constantine with Orations of Constantine and Eusebius.: Chapter XVIII

Chapter XVIII.—That after the Abdication of Diocletian and Maximian, Constantius became Chief Augustus, and was blessed with a Numerous Offspring.

The immediate consequence of this conduct was a recompense from the hand of God, insomuch that he came into the supreme authority of the empire. For the older emperors, for some unknown reason, resigned their power; and this sudden change took place in the first year after their persecution of the churches. 3086

From that time Constantius alone received the honors of chief Augustus, having been previously, indeed, distinguished by the diadem of the imperial Cæsars, 3087 among whom he held the first rank; but after his worth had been proved in this capacity, he was invested with the highest dignity of the Roman empire, being named chief Augustus of the four who were afterwards elected to that honor. Moreover, he surpassed most of the emperors in regard to the number of his family, having gathered around him a very large circle of children both male and female. And, lastly, when he had attained to a happy old age, and was about to pay the common debt of nature, and exchange this life for another, God once more manifested His power in a special manner on his behalf, by providing that his eldest son Constantine should be present during his last moments, and ready to receive the imperial power from his hands. 3088

Footnotes

The persecution was in 303 or 304. Compare discussion of date in Clinton, Fasti Rom. ann. 303–305. The abdication was in 305.

Eusebius uses the terms Augustus, king, autocrat, and Cæsar with a good deal of interchangeableness. It is hard to tell sometimes whether king (βασιλεύς) means emperor or Cæsar. In general, Augustus has been transferred in translations, and king and autocrat both rendered emperor, which seems to be his real usage.

Constantine reached him just before his death, though possibly some weeks before. Compare Prolegomena.