Why Constantinople Became the Second Rome

Why Byzantium Prospered with its Capital on the Bosphorus

The fishing was easy near Constantinople. Here, Byzantines "fire-fish," in which a burning fire basket was mounted onto the end of the boat at night. The light would attract the fish closer to the surface of the water allowing the fisherman to see their catch more easily This is a miniature from Cynegetica, by Oppian of Apamea (or Pella) (active 3rd century AD), manuscript Venice, Marc. Gr. Z 479. Greece, 11th century.

The nondescript town of Byzantium, a Greek colony of Megara (Dorian city), was founded before 3000 B.C. Byzantium was an important center for trade on the Black Sea and was not typically thought of as having importance in Mediterranean affairs. Though it was of little importance in the Roman Empire, for which trade on the Pontus Euxine was a sideshow, it became a major world center during the Middle Ages. It remains a world capital, now renamed Istanbul. This is because the ancient Romans specifically chose it as their new home as the situation in Italy deteriorated. There were several reasons why Byzantium was a good location for a second (and ultimately only) capital of the Roman Empire.

Byzantium was considered part of the Black Sea (Pontus Euxine) sphere, not the Mediterranean.

Rome was not very defensible. It was a problem of the region, not just the city itself. At the height of the Roman Empire, the idea of invaders capturing and sacking Rome was absurd. However, this changed as Rome's foes accumulated just across the border (and, in many cases, within the borders). The western Romans themselves realized this and eventually moved the true (military) capital to Ravenna, which was more easily defensible. The first major recognition of this was when Emperor Diocletian (r. 284–305), who ruled before Constantine and began the process of dividing the Empire, chose to rule the eastern half for reasons which we'll get to below. However, he chose Nicomedia as his capital before retiring to his palace near his Salona birthplace in the seaside town of Aspalathos (now Split, Croatia). Thus, there were different options for the new capital, some of them at the time arguably as good as Byzantium. However, the inherent benefits of Byzantium prevailed.

Constantine the Great chose Byzantium as Rome's new capital.

The Advantages of the East

The emperor Constantine (r. 324–337) chose the Byzantium as the new capital for a reason. The eastern half of the empire, which eventually became the Eastern Roman Empire, had various advantages in general over the Western Roman Empire. The pars orientalis had been a major center of civilizations long before Italy. Thus, it had densely populated, wealthy, and more ancient cities (e.g., Cairo, Damascus, Aleppo, Edessa, Jerusalem, Ephesus, Smyrna, Nicaea, Alexandria, Antioch, Caesarea) than the western regions.

The Rhine-Danube corner in the Roman frontier (ziegelbrenner).

Of course, not all was sweetness and light in the east. The new Sassanian dynasty was more aggressive than the Parthians and had become a major distraction for the later Roman emperors. The barbarian tribes from the steppes were pressing against the Limes Transalutanus, Limes Rhaetia, and Limes Moesiae on the Danube frontier and the frontier defenses had become inadequate. In addition, the predominant language in the region was Greek, not Latin. All of these problems could be overcome, however, through various methods.

After pondering the matter at length, Constantine put aside other options such as Troy and perhaps Chrysopolis. One of the major deciding factors for Constantine's decision had nothing to do with geography or military considerations. In his later years, Constantine was a deeply religious man (for most of his life a pagan, Constantine believed that he owed his victory at the Battle of the Milvian Bridge to Christian divine intervention). It was no secret that the new Christian religion had taken hold to a much deeper degree in the east than in the west. This made the populations of the east more reliable and less likely to switch allegiances based on considerations such as money or prestige. In a word, the population was more controllable.

This map shows the location of Constantinople at the lower left, with the Golden Horn directly above it and the route to the Black Sea heading off to the upper right (Kaidor).

Natural Advantages of Byzantium

Let's go through ten reasons why Byzantium was prime real estate throughout the Middle Ages.

First, being situated at the crossroads of two continents—Europe and Asia—and two seas—the Black Sea and the Mediterranean Sea—gave Constantinople major advantages. it was located on the trade routes from the East. Whether they came by land or via the Black Sea, goods from the East were going to have to pass through Constantinople. That meant an assured stream of customs revenue.

The Theodosian Walls stopped invaders for a thousand years. The only time they were breached, in 1204, was by a naval attack.

Second, the location of the city itself on a peninsula made it naturally defensible. Constantinople could only be approached on land from the north and west. This area funneled down to a very narrow area that was soon fortified. You can say many negative things about the Romans and Byzantines, but you can't say they were bad wall builders. In fact, the Byzantines were probably the best military wall builders of all time. The defenses were amplified by closing off the Golden Horn and building the Theodosian Wall along the neck of the city. The Bosphorus always proved handy to slow down the routine invasions from the East because invaders from that direction often did not have a fleet. To capture Constantinople, an enemy had to have both an army and a superior fleet - a rarity in the middle ages. Attackers who had only an army - such as the Arabs - or a navy - such as the Venetians - could do little against Constantinople's walls.

Third, the East was the source of much of the Roman Empire’s wealth. Trade routes from the Pacific and Indian Oceans converged on Constantinople. There were gold mines, spices, fertile lands in Asia Minor, all sorts of natural wealth in the East. Egypt was the granary of the Roman Empire, although it was lost fairly early on in the life of the Eastern Empire.

Fourth, at least at the time of its founding, most Roman enemies were far away. The Germanic tribes were heading toward Gaul, not particularly toward Asia Minor. The Persian Empire (Sassanian era) was in the East, but the Romans always had a handle on it and the Persians had an awfully long march just to get to the Bosphorus. Of course, over time that situation changed drastically until it seemed as though enemies in Europe and Asia always were attacking Constantinople, but that’s where success gets you.

Fifth, the priority at the time of Constantinople's found had become solid defenses. Following the cataclysmic issues of the Third Century, the Romans weren’t going to choose somewhere they couldn’t easily defend. That ruled out an awful lot of choices. There were many nascent power centers developing in Gaul and northern Italy which weren’t going away, walled towns each with its budding Caesar. By contrast, the tribes of the Balkans were technologically backward and at Constantinople, there weren’t any nearby power centers - and most of those were far away on the other side of the Bosphorus. The Romans could leave the little satraps in Pisa or Genoa or Milan in the rearview mirror forever by moving to Constantinople.

Abydos controlled access between the Black (Euxine) Sea and the Aegean.

Sixth, simply controlling crossings across the Bosphorus, regardless of trade, gave Constantinople natural political and economic leverage. This came in very handy during the early and late Crusades, for instance (not so much the Fourth Crusade, though). The ports and customs of Abydos (Hellespont) and Hieron, south and north of Constantinople respectively, were a source of continual revenue. Of course, at times this trade caused problems - such as when the Black Death arrived, which savaged Byzantium and later all of Europe - but overall thriving trade was a major reason for the Eastern Empire's survival.

Seventh, centering on the border of Europe and Asia kept the Romans’ hand in both pots. It “kept their options open.” While it is common to think of the Byzantines as fops wearing lots of gaily colored silks, at many times, such as during the reign of the Comneni in the 12th Century, the Byzantines were extremely western in their orientation and positively warlike. They had jousting tournaments and falconry and all that stuff just like in Merry old England.

Eighth, Constantinople had a very mild climate. There were nice sea breezes, it never got too cold, you didn’t get cooped up in drafty castles all winter, it wasn’t in the desert - such as Jerusalem or Edessa or Antioch or the other cities in the East. It was pleasant. That counts for a lot.

Ninth, in terms of its location, Constantinople was a central spot in the east. An army encamped at Constantinople could just as easily head north to battle the Bulgars or south to battle the Persians or west to battle invading Italians. The Romans built an efficient military road network that still exists in many places. A central location amplifies your military resources.

Byzantine fishermen using a net. This is a miniature from a Lectionary, 13th century. © Instituto Ellenico di Studi Bizantini e Postbizantini di Venezia.

Tenth, the Golden Horn was bountiful for fishing. You literally had an inexhaustible food source that was practically under your nose and which nobody could ever take away from you. The Byzantines were excellent fishermen and perfected techniques for preserving fish. Putting a chain across the mouth of the Golden Horn protected the fishing boats that fed the city from any invader. The River Lycus provided fresh water. The Byzantines need never succumb to a siege, and their enemies knew it.

So, there were many reasons to create a second capital at Constantinople rather than somewhere else, and probably many more beyond the ones I’ve listed. One can’t fault the choice, the Eastern Empire did, after all, last for a full 1000 years.

2019