As the direct agent of God, the emperor was responsible for preserving the tradition of Roman law. Only the emperor could modify the laws already in effect or proclaim new ones. Thus he had on hand an immensely powerful instrument for preserving and enhancing power.
Byzantium and Islam
After Constantine, Byzantium called itself New Rome. Its emperors ruled in direct succession from Augustus. Yet many non-Roman elements became increasingly important in Byzantine society. A Roman of the time of Augustus would have been ill at ease in Byzantium. After Constantine had become a Christian, the emperor was no longer a god; but his power remained sacred.
At the far southeastern corner of Europe, on a little tongue of land still defended by a long line of massive walls and towers, there stands a splendid city, Istanbul. After 330, when the first Christian Roman emperor Constantine the Great made it his capital, it was often called Constantinople, but it also retained its ancient name Byzantium. For more than eleven hundred years thereafter it remained the capital of the Eastern Roman Empire.