Constantinus autem ex se Byzantium Constantinopolim nuncupavit ob insignis victoriae memoriam. Quam velut patriam cultu decoravit ingenti et Romae desideravit aequari. In commemoration of his splendid victory, Constantine called Byzantium ‘Constantinople’ after himself; and as if it were his native city, he adorned it with great magnificence and wished to make it equal to Rome (Origo Constantini Imperatoris, 6.30).

An anonymous author wrote a biography about the life of Constantine a few years after the emperor’s death that asserted that Constantine founded Constantinople to commemorate his 324 A.D. victory against Licinius in Chrysopolis (mod. Üsküdar). The Battle of Chrysopolis was the last battle in the war between Constantine and Licinius, the co-emperors of the Tetrarchy. The first battle of this final war was fought in Hadrianopolis during the summer of that same year. This essay will offer a descriptive narrative that examines the causes and consequences of the Battle of Chrysopolis as is important to the urban history of modern Istanbul.The series of complex events that led Constantine and Licinius into direct rivalry began in Milan about ten years before the final battle. The two met in February 303 and decided on a new imperial policy particularly aimed towards Christian subjects. This meeting was also an opportunity to establish an additional alliance through marriage; Constantine had his sister Constantina married to Licinius. The Milan Meeting left Licinius in charge of large parts of the Balkan lands while Constantine received Italy and the rest of the western lands. However, Constantine had greater ambitions and wanted to become the sole ruler of a unified empire. He set out to create that empire through a series of administrative attempts, which significantly antagonized his relationship with Licinius. These attempts led to a local conflict that soon became a major battle in Cibalae (Vinkovci in Crotia) on October 8, 315. Licinius lost the battle and retired first to Sirmium (Sremska Mitroviça) then to Serdica (Sofia). In the subsequent peace treaty, Licinius lost much of the Balkans and ultimately transferred his capital to Nicomedia where he remained for the next seven years. He reemerged for the final battle against Constantine in 324.

A dissident group of Christians was one of the many factors forcing these two co-emperors into this final battle. The debates surrounding the divinity of Jesus Christ—leading up to the First Council of Nicea in 325—were deeply divisive within the Christian community. To prevent disorder in the cities, Licinius banned the ecclesiastical meetings of bishops. Never one to miss an opportunity, Constantine immediately became a defender of Christians. In a public address in Serdica in the early 320s, Constantine provocatively compared Licinius to the early persecutors of the Church. It seems that Constantine was seeking a pretense for a new war with Licinius. A real opportunity appeared in 323. While Constantine was in Thessaloniki, a Sarmatian war band broke into the Danube and plundered Thrace and Moesia. In response to this assault, Constantine personally led an expedition pursuing the Sarmatians up to the north of the Danube. During this skirmish with the Sarmatian nomads, Constantine did not respect the border agreement and from time to time crossed over into Licinius’ territory. In response, Licinius refused permission for coins minted in the name of Constantine to be distributed in the east. These events further enflamed the rivalry and, in the end, formed the background of the Battle of Chrysopolis.The first battle of the final war between the two emperors was fought on the banks of Hebrus in Hadrianopolis. Licinius defended the eastern banks of the river while Constantine was on the western side. On July 3, 324, Constantine decided to cross the river. Licinius could not hold his position and retreated to Byzantium by night. The next day, an important section of Licinius’ army surrendered to Constantine. Meanwhile, Licinius directed his significant naval forces to protect the Hellespont against a much smaller fleet commanded by Crispus, Constantine’s oldest son. However, Licinius’ admiral lost the sea battle against Crispus. Shortly afterwards, Crispus’ fleet arrived on the shores of Byzantium. Licinius relinquished Byzantium and, with most of his army and treasures, withdrew to Chalcedon. While laying siege to the city by land and sea—and in reaction to the city’s refusing to surrender—Constantine also seized an opportunity to cross the Bosphorus. Licinius failed to prevent Constantine from advancing, and the latter met Licinius’ fleet on the shores of Byzantium. Constantine’s army successfully crossed to the eastern side of the Bosphorus near the mouth of the Black Sea at a northern point about two hundred stadia (approx. 35 km) from Chalcedon. The spot where Constantine’s army crossed the strait was a holy place and, as noted by the geographer Strabo, belonged to the Chalcedonians.After crossing, Constantine’s army advanced into the hills around present-day Beykoz and began to march south. Licinius realized the province of Bithynia was now in danger and began to advance his army north for the final confrontation. On September 18, 324, a fierce battle ensued in Chrysopolis located between Chalcedon and the holy place. Here, according to sources, many of Licinius’ troops (approx. 25,000) were killed. A defeated Licinius retreated hastily and Constantine entered Nicomedia in triumph. The city of Chalcedon opened its gates to the Constantinian forces and Byzantium followed suit. The Byzantine citizens knew the consequences of supporting the loser of a battle; 130 years previously, during the war between Septimius Severus and Pescennius Niger, Byzantium had supported the loser and paid a heavy penalty.

1- The Great Constantine (Istanbul Archeology Museum, Coins Section)

Constantine won a decisive victory that not only determined the future destiny of Byzantium, but also had great impact on the future of Christianity and the history of Europe. Constantine very quickly perceived that an empire which had frontiers from the Danube to the Euphrates could be administered most effectively from a strategic location like Byzantium. While fifth-century sources like Sozomenus and Zosimus report that Constantine first chose Troy as his new capital and even started to expand the city, another source—Origo Constantini Imperatoris—claims the emperor decided to rebuild Byzantium as the new capital on November 1, 324. Whether Troy’s importance in the pagan tradition discouraged Constantine from naming it his new capital is difficult to tell. Sozomenus notes that traces of Constantine’s endeavors in Troy were visible even in his day. Zosimus argues that changing the new capital from Troy to Byzantium was a result of strategic factors and he places Constantine’s search for a new capital within the context of the scandal that broke out in the palace; Constantine’s wife Fausta and his son Crispus were put to death amidst accusations of adultery. Finally, there are also mythological stories that support choosing Byzantium as the capital. According to one medieval tale, when Constantine began to fortify Chalcedon, an eagle snatched a stone from the incomplete building and carried it to Byzantium. Constantine considered this a divine omen and decided to change his earlier plan in favor of Byzantium.

Among sources, only the record of Origo Constantini Imperatoris can be considered close to reflecting the true nature of events; other sources confirm Origo’s assertion that construction started prior to the end of 324. Constantine’s aim was for Constantinople to function as an alternative to Rome. To this end, he stripped the Aegean cities of their monuments and invited rich patrons from cities in Asia Minor to Constantinople. Yet another source claims the empire’s treasury almost collapsed because Constantine spent so much money reconstructing Byzantium. He also established a senate, the members of which were called clari instead of the Roman term clarissimi. To put all of this in context, Licinius would not have needed to construct a new Eastern capital if he had won the battle because he had already chosen Nicomedia as his headquarters.

In conclusion, the Battle of Chrysopolis was the decisive factor in the establishment of Constantinople as the flourishing, governing city of the Balkans and the Mediterranean lands for the next millennium.


Barnes, T.D., Constantine and Eusebius, Cambridge: Harvard University Press, 1981.Kaçar, Turhan, “Üsküdar Savaşı ve Bizans’ın Temelleri”, Üsküdar Sempozyumu I: 23-25 Mayıs 2003: Bildiriler I, edited by Zekeriya Kurşun et al., Istanbul: Üsküdar Belediyesi, 2004, vol. 1, pp. 21-28.

Millar, F., The Emperor In the Roman World, London: Cornell University Press, 1992.Pears, E., “The Campaign against Paganism A.D. 324”, The English Historical Review, 1909, vol. 24, no. 93, pp. 1-17.

Valesianus, Anonymus, “Origo Constantini Imperatoris”, Valesius Seçkileri, tr. Turhan Kaçar, Istanbul: Kabalcı, 2008, pp. 28-45.

This article was originally written in English for History of Istanbul and published in a digitalized form in 2019; and its Turkish translation was published in 2015

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