After Rome ceased to be a republic the emperors more than once wanted to transfer the capital from republican-minded Rome to the East. According to the Roman historian, Suetonius (I, 79), Julius Caesar intended to move from Rome to Alexandria or to Ilion (former Troy). In the first centuries of the Christian era the emperors often deserted Rome for long periods during their extensive military campaigns and journeys through the empire. At the end of the second century Byzantium received a heavy blow: Septimius Severus, upon defeating his rival, Pescennius Niger, who was supported by Byzantium, submitted the city to a terrible sack and almost complete destruction. Meanwhile the East continued to attract the emperors. Diocletian (284-305) preferred to live in Asia Minor in the Bithynian city, Nicomedia, which he beautified with many magnificent new edifices.
When Constantine decided to create a new capital, he did not choose Byzantium at once. For a while, at least, he considered Naissus (Nish) where he was born, Sardica (Sofia), and Thessalonica. His attention turned particularly to Troy, the city of Aeneas, who according to tradition, had come to Latium in Italy and laid the foundations for the Roman state. The Emperor set out personally to the famous place, where he himself defined the limits of the future city. The gates had already been constructed when, as Sozomen, the Christian writer of the fifth century, related, one night God visited Constantine in a dream and induced him to look for a different site for his capital. After this Constantine's choice fell definitely upon Byzantium. Even a century later travelers sailing near the shores of Troy could see the unfinished structures begun by Constantine.