Why did Constantine build Constantinople?

Rome had stopped being the capital

By Constantine’s time, Rome had not been the empire’s working capital for decades. The fighting was on the Rhine, the Danube and the Persian frontier, and the richest provinces lay in the East. In 293 Diocletian had split power among four rulers based at Trier, Milan, Sirmium and Nicomedia, each close to a threatened border. Rome remained the symbol. It was no longer where decisions were made. Lactantius, a Christian teacher at Diocletian’s court, complained about what the new system cost.

For he made choice of three persons to share the government with him; and thus, the empire having been quartered, armies were multiplied, and each of the four princes strove to maintain a much more considerable military force than any sole emperor had done in times past.

Nicomedia, Diocletian’s own capital, lies about 100 kilometers (60 miles) east of Byzantium. When Constantine chose a seat of his own, he chose the same corner of the map.

The battle that chose the site

In 324 Constantine fought Licinius, the last rival emperor, for the East. His forces beat Licinius at Adrianople, again at sea in the Hellespont, and finally on September 18 at Chrysopolis, on the Asian shore of the Bosporus, looking across at Byzantium. Now he ruled the whole empire, and that same year work began on a new city on the European side.

Byzantium was an old Greek trading town, and its site had been admired for centuries. Polybius, in the second century BC, judged it the best placed of any city he knew for safety and wealth by sea, though badly exposed by land. Water guarded three sides: the Sea of Marmara, the Bosporus and the Golden Horn, a deep natural harbor. Every ship between the Black Sea and the Mediterranean passed beneath it, and the land road from Europe into Asia crossed here. From it an emperor could reach either of his great frontiers, the Danube or Persia.

A second Rome, built in a hurry

Constantine modeled the new city on the old one. It was divided, like Rome, into fourteen regions. It had a senate of its own, a hippodrome for chariot races, a great palace and, from 332, free grain for its citizens, as Rome did. The building went at speed, and columns, marble and statues were carted in from all over the empire. Jerome wrote in his Chronicle that the city was dedicated by stripping almost every other city bare. One prize still stands in Istanbul’s old Hippodrome: the bronze Serpent Column, made at Delphi after the Greek victory over Persia at Plataea in 479 BC.

Was it meant to be a Christian capital? Constantine built churches there, among them the Church of the Holy Apostles, where he chose to be buried. But on top of his porphyry column in the new forum stood a statue of the emperor himself as the sun god Helios, crowned with rays. The column, finished around 328, still stands; its statue fell long ago. Historians still argue over how Christian the city was meant to be (who Constantine was).

What the move achieved

On May 11, 330, after six years of work, he dedicated it: Constantinople, the city of Constantine. It became the anchor of the eastern half of the empire, which outlived the West by almost a thousand years (why the East survived). It fell to the Ottomans in 1453 (when Constantinople fell), and today it is Istanbul (what it is called today).