“On May 11, 330, the Emperor Constantine inaugurated the ‘New Rome which is Constantinople,’ to share with Rome, as co-capital, the administration of his huge empire. From its inception three complementary elements characterized the new city: Greek language and culture; Roman law and administration; and Christian faith and organization. While the western half of the empire survived only another century and a half, the eastern empire continued on its own for another thousand years, until 1453. It became an empire in its own right, later called Byzantium after the name of the Greek city around which Constantinople was built.
Like the west, the east had to withstand military attack. Germanic tribes crossed the Danube, but found Constantinople impregnable, defended behind huge walls built by the Emperor Theodosius II (r. 408-450). Using the German mercenaries, the eastern emperor Justinian I (r. 527-565) recaptured many of the western regions including North Africa, southern Spain, Sicily, Italy, and even Rome itself, but costs in wealth and manpower crippled his empire. After his death most of these western conquests were lost, while the Persians constantly warred with the remnants of the Roman Empire in the east. Justinian’s legal, administrative, and architectural initiatives produced more lasting results. He had the Roman system of Civil Law codified in four great works, known collectively as the Justinian Code, thus helping to perpetuate an administration of great competence. In time, the Code became the basis for much of modern European law. He adorned Constantinople with numerous new buildings, crowned by the Church of Hagia Sophia, the Church of Holy Wisdom. He had churches, forts, and public works constructed the empire.” ~ The World’s History