Constantine I the Great

   First Christian emperor (q.v.), who reigned from 306-337. Proclaimed augustus (q.v.) in York in 306 by his dying father Constantius Chlorus (q.v.), Constantine gained control of the West by defeating Maxentius in Rome (qq.v.) at the battle of the Milvian Bridge in 312. In 324 he gained control of the entire empire when he defeated his eastern rival Licinius (q.v.) at Chrysopolis in Bithynia (qq.v.). He converted to Christianity (in 312 according to the famous story in the Vita Constantini [q.v.] by Eusebios of Caesarea [q.v.]), and he thereafter showed a favoritism to the Christian church (e.g., he constructed churches at state expense and allowed the church to accept bequests) that put Christianity on the road to becoming the state religion by the end of the fourth century. The role he played in church affairs, especially in the controversies over Donatism and Arianism (qq.v.), became a prototype for future church-state relations. This was seen especially at the Council of Nicaea (q.v.). The new imperial residence at Byzantion (q.v.), founded in 324, would soon acquire the name Constantinople (q.v.), the "city of Constantine," and become the capital of the eastern half of the empire. Constantine perfected the administrative reforms of Diocletian (q.v.) by dividing the empire into four prefectures (q.v.), each administered by a praetorian prefect (q.v.), whose duties were only civil. Dioceses and provinces (qq.v.) remained as before. However, he separated the civil and military functions in each prefecture (q.v.); now each praetorian prefect had a magistri militum (qq.v.) in charge of military forces. In 312, he disbanded the old Praetorian Guard, greatly enlarging the mobile field forces, the comitatenses (q.v.). He reformed the currency, issuing a gold solidus (q.v.) that remained the "dollar" of the Mediterranean (q.v.) for almost a millennium. He was baptized in 337 as he lay dying by Eusebios of Nikomedia (q.v.), having changed the Roman Empire more than any emperor since its founder Augustus.