What Events Led to the Fall of Constantinople in 1453 CE, and What was the Role of Mehmed II and Orban in it?

After 1500 years of rule, the final bastion of the Roman Empire was attacked by Ottoman forces.

Emperor Constantine
The Ottomans

Rome’s final stand

In 330 CE, the Roman Empire stretched all the way from the shores of Britain to the sands of Egypt. The capital at that time was the city of Rome, which was well-positioned to rule the western portion of the territory, but less convenient for lands in the east. To solve this problem, Emperor Constantine ordered the construction of a second capital – Constantinople – at the edge of modern Turkey.


Constantinople became a magnificent seat from which Roman emperors could rule the eastern portion of their empire. It was famed for its vibrant culture, scholarly attitudes, and colossal, fortified walls. This seat survived for more than a thousand years, with Romans ruling in Constantinople as late as 1453 CE. This far outstripped their presence in Rome, which fell to barbarian forces in 476 CE.

In other words, when people talk about the collapse of the Roman Empire in the 5th century, they are only telling part of the story. A version of the Roman Empire survived in Constantinople, safely protected by its fortified walls. It later became known as the Byzantine Empire, named after a Greek colony, Byzantium, which had previously existed in the place where Constantinople was built.

Rise of the Ottoman Empire

In the 13th century, a new force began to stir in the region of Anatolia, not far from the walls of Constantinople. This force was small but ambitious: a Muslim tribe who lived on the outskirts of the Byzantine Empire. They were known as the Ottomans, a term derived from the name of their leader: Osman I.


Osman was a powerful and charismatic leader. Throughout 19 years of rule, he led his tribe on a course of rapid territorial expansion. There are no surviving accounts of these events, and historians don’t know how such a minor tribe managed to expand so ferociously, but the Ottomans managed to seize control of several regions, including a number of Byzantine towns.

Osman’s successors continued what he had started. They expanded into Europe, claiming territory in Macedonia, Kosova, Bulgaria, Hungary, Serbia and Greece. But Constantinople, the glittering jewel of the Byzantine Empire, eluded them; its colossal walls were seemingly unsiegeable, and any attempt would have inevitably ended in defeat.

Mehmed and Orban

In 1444 CE, Mehmed II, a direct descendant of Osman I, ascended to the Ottoman throne. He was young and ambitious, and probably gay; he enjoyed collecting beautiful men and keeping them as personal prisoners. Like many before him, Mehmed aspired to invade Constantinople, but he knew it would be useless to send his forces thrashing against the city’s walls.

This changed in 1453 CE, when Mehmed was approached by a Hungarian engineer named Orbán. Orbán was an expert in gunpowder weaponry, a new technology which had only arrived in Europe during the 13th century. He offered to build a cannon for the Ottomans, a weapon more powerful than anything the world had seen before, with enough strength to shatter even the tallest fortified walls. Mehmed grabbed this opportunity, paying Orbán handsomely for his work.

Orbán built the cannon in three months. The weapon was named Basilic, and had the power to fire hefty cannonballs over a distance of more than a mile. It was so large that it needed 63 oxen and 400 men to drag it to Constantinople.

Fall of Constantinople

Mehmed II attacked Constantinople on 6th April 1453. His forces heavily outnumbered the Byzantine defenders: 80,000 Ottomans against 40,000 Byzantines, the majority of which were armed civilians rather than professional soldiers. Under normal circumstances, the Byzantines would still have been confident of defending the city, but the Basilic cannon changed things.

The cannon blasted through the walls, just as Orbán had promised. The defenders managed to hold the breach, but the Ottomans simply blasted another hole. Again, the defenders managed to hold, but the Ottomans blasted another. The bombardment lasted for 53 days, until there were too many breaches for the Byzantine forces to defend. Their resistance crumbled, and the Ottomans entered the city.

The Byzantine emperor was killed in battle, and Mehmed claimed the city as his own. He changed its name to Istanbul. After a period of almost 1500 years, the final bastion of the Roman Empire had collapsed.

European Renaissance

When the western portion of the Roman Empire had originally fallen to barbarian forces, a significant number of scientific texts had been lost or destroyed, many of them dating all the way back to the golden age of Ancient Greece. This led to an era of intellectual decline across Europe, as people struggled to cope without the collected learnings of the ancients.


owever, many of those texts were preserved within the walls of Constantinople. And after the Ottoman invasion, Byzantine scholars fled to Europe, bringing copies of these texts with them. This rapid influx of ancient wisdom inspired a wave of progress, with men like Galileo, Da Vinci, Kepler and Descartes making discoveries which changed the world. This period is often known as the Renaissance – a rebirth of European science. The fall of Constantinople wasn’t the only cause, but it certainly helped.

Progress was also made in the east, especially in terms of warfare. The Ottomans continued to use gunpowder weapons to bolster their military, and other nations quickly adopted these new technologies, changing the nature of warfare forever.

What if the Byzantines had won?

If the Byzantines had successfully fended off the Ottomans, then that final sliver of the Roman Empire would have survived for a little longer, and might even have endured to the present day. That would have been a remarkable achievement, making it the longest-lasting continuous empire in all of human history.


With its stockpiles of ancient texts, the victorious city of Constantinople might have enjoyed its own Renaissance period, with Byzantine scholars making groundbreaking discoveries in the arenas of science and medicine. Without the Byzantines that fled to Europe, European scholars would have fallen behind, with the Dark Ages continuing in many of these regions.

In later years, the Renaissance period gave Europe the impetus to explore the world, conquering parts of the Americas, Asia, Africa and Australasia. If the Renaissance had taken place in Constantinople instead, the Byzantines might have been the ones to conquer these far flung places, building a new Roman Empire even larger than the one which had existed centuries earlier.

Byzantine sources

Historians have access to a number of sources from Byzantine citizens. The most comprehensive of these comes from Nicolò Barbaro, a Venetian physician who was present throughout the siege. This source was written in the form of a diary, with regular entries giving a detailed account of the day-by-day progress of the battle. For example, he described how the Ottomans “came on behind the smoke of the cannon, raging […] like wild beasts.”

Barbaro’s text is far from perfect. As a Venetian, he hated people from the rival city of Genoa, and this attitude muddies his entire account. At one point, he tried to pin the failure of the city’s defenses on a Genoese commander who cowardly abandoned his post, while other sources explain that this commander was actually injured by an Ottoman arrow, and only left his post with great reluctance.

It is likely that additional Byzantine sources will be discovered in the near future. When Byzantine citizens fled to Europe, they left accounts of their experiences in libraries and archives, some of which are yet to be properly explored and documented.

Ottoman sources

While there are plenty of Byzantine sources to work with, Ottoman accounts are far more difficult to come by. The vast majority of Ottoman witnesses would have been illiterate soldiers, in contrast to the Byzantine witnesses, which included thousands of civilians in the besieged city, many of whom were educated enough to write things down.

The closest thing to an Ottoman source is the writing of Konstantin Mihailović, a Serbian cavalryman who served as part of the Ottoman army during the siege of Constantinople. However, his perspective wasn’t truly Ottoman, and he only took part in the battle reluctantly: Serbia was part of the Ottoman Empire at the time.

An Ottoman viewpoint might still be discovered in the future. Marios Phillipides, a modern historian, writes about “Ottoman libraries and manuscript collections that have thus far been overlooked.” All around the world, there are collections of documents which have never been properly studied and translated, which means an Ottoman source might be out there – it simply needs to be found.

The East-West Schism

In some ways, the Siege of Constantinople was a battle between Islam and Christianity, just like the Battle of Tours many centuries before it. But the situation was more complex in 1453 than it had been previously, following the East-West Schism in 1054 CE.


When Constantinople was first founded, the Byzantines had established a religious representative with similar powers to the Pope in Rome. This representative – the Patriarch – became a source of tension over the centuries which followed, as the office of the Pope and the office of the Patriarch clashed over details of the faith. For example, the Papacy believed that clerics should remain celibate, while the Patriarchy firmly disagreed.

In 1054 CE, the two sides decided to officially cut ties, with Christianity divided into separate halves: the Roman Catholic Church, run by the Pope, and the Eastern Orthodox Church, run by the Patriarch. When the Ottomans clashed with the Byzantines, these were Eastern Orthodox Christians. The Roman Catholics, in western Europe, were not involved.

Fall of the Ottoman Empire

After the Siege of Constantinople, the Ottoman Empire survived for hundreds of years, well into the modern age. Remarkably, they took part in World War One, and fought a battle at Megiddo, following in the footsteps of the Ancient Egyptians. Their leader during World War One was Sultan Mehmed VI, from the same bloodline of Mehmed II, the man who conquered Constantinople.

The Ottomans chose to ally with Germany, which meant they ended up on the losing side of the conflict. They lost almost 500,000 soldiers during the course of the war, and saw their territories divided between Allied forces. Mehmed VI was forced to flee to Malta, and the empire was replaced by the modern state of Turkey.

If the Ottomans had sided with the Allies instead of Germany, the empire might have survived to the present day. However, there were already signs of Ottoman weaknesses before the outbreak of World War One, with low literacy rates, weak industries, and dissatisfied subjects. The Ottoman Empire had probably reached the end of its lifespan, and World War One was just the final nail in the coffin.

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