Early career
A Bishop Near the Throne
Nothing certain is known of Eusebius's birth. The historian Ammianus Marcellinus says he was a distant relative of the future emperor Julian, and so of Constantine's family. Like Arius, he seems to have studied under Lucian of Antioch. He was first bishop of Berytus, modern Beirut, and then moved to Nicomedia, where the eastern emperor Licinius held his court.
Church custom frowned on a bishop leaving one see for a greater one, and the bishops at Nicaea soon forbade it, but Eusebius made such moves throughout his career. He was close to Constantia, the wife of Licinius and half-sister of Constantine, and influence at court was the source of his power.
Loading the rest of this biography