The Theodosian Walls and Fall of Constantinople
- My Istanbul Guide
- Aug 21
- 6 min read
Having retired after doing their duty for fifteen hundred years, protecting the city, Istanbul's walls are still standing proud and strong. A stroll along (and sometimes on top of) the city walls would bring one to the past of the glorious defenses!
The city of Constantinople is on the tip of a peninsula, surrounded by water on two sides. The city is protected by strong walls, covering all three sides of it. The walls along the Golden Horn stretched for 7 kilometers, those along the Sea of Marmara for 7 kilometers, and the land walls for 5.5 kilometers. In total, 20 kilometers of walls protected the city. In this tour, we will be covering the southern half of the land walls. Starting in the middle of them, and then finishing at the southern end, where we will visit the Seven Towers Fortress (Yedikule). We will be covering roughly about 3,5 kilometers, or 5000 steps.
The year is 1451, and the 19 year old Mehmed the Second rises to throne as the new Ottoman Sultan. He is a young and ambitious man and he needs to prove himself to the veziers and other bureucrats under him. So, he needs to hit a big success to prove that he is a worthy ruler. He sets his eye on the pearl of the Romans, the city of Constantinople.
Although being the wealthiest and the most civilzied city of the late Roman and medieval world for more than 1000 years. the city of Constantinople had been in a long period of decade in the 15th century. Inner conflicts between the ruling dynasties and many invasions from all around had eaten away the lands of the empire in the Balkans and Anatolia. At the onset of the Siege, the city was in the middle of a Turkish sea all around. The Ottoman Turks had conquered the Balkan and Western Anatolian provinces of the Byzantine empire already. Now, it was the city of Constantinople that Mehmed the Second set his eyes on.
Although having been sieged by a number of armies throughout its history, including Arabs, Goths, Bulgars, Rus, Avars, Huns, and more; the city of Consantinople had never fallen except for one case which we will tak about later. The thing that protected the city was the formidable and complex set of walls, mainly built during the time of Theodosius II between 408 and 413.
The Walls consisted of three main layers. The main wall, outer wall, a low wall and the moat. The main wall would rise up to 12 meters high and had 96 defense towers about 18-20 meters tall every 55 meters.
The Outer wall would rise 8,5 meters with 96 defense towers as well.
The Moat was 10 meters deep and 20 meters wide, and could possibly be filled with water when needed.
These set of fortifications proved a very effective method and they had served the city very well through its past until the Ottomans came with new siege tactics. The secret was the supercharged upgrade of gunpowder and crazy sized guns to fire 200-300kgs of cannons onto the walls. The Ottomans didn’t need to climb over the walls to take over the city; they were going to tear down the walls to make their way in to the city!
We need to mention one important man that changed the course of history here. The person we mean is the Hungarian cannon founder and engineer Orban. This crazy man had the idea to cast huge guns to fire massive cannons. He first went to the Byzantines with his ideas, but was rejected by them due to the lack of funds. Mehmed II, however, happily accepted his services and granted him the means to work. The Ottomans had already been using cannons to siege fortifications before. They even had a unit for artillery, called ‘Topçular’ in Turkish.
At the beginning of the Spring of 1453, the Ottoman army camped outside the city walls and began their preparations with 80,000 strong army. They also brought the massive 4,5 tonnes heavy bombard Orban had built in the then-Ottoman-capital of Adrianople (modern day Edirne in Türkiye). The gun was dragged by sixty oxen to the siege.
The Byzantines were heavily outnumbered by the sieging Ottomans (10,000 defenders against 80,000 siegers). However, they were also aided by the Genoese and Venetian ships and soldiers. The siege lasted about 50 days. Although the defenders fought bravely and vigorously, the Ottomans finally managed to tear down the middle section of the walls eventually and began entering the city through the walls. The city fell shortly afterwards. The last emperor of the Byzantines, Constantine XI Palailogos, died defending the city, instead of fleeing with the Venetian ships.
Istanbul is often referred to as ‘The City of Seven Hills,’ in reference to Rome.This hilly topography, while bringing some advantages, also brought a major drawback in the defense of the city. At the approximate midpoint of the land walls, observe how the terrain forms a narrow dip toward the city's center. This depression marks the course of the Lycus River, which historically flowed into the city from outside the walls. This river no longer exists, but its course roughly corresponds to today’s Vatan Boulevard. This dip causes that section of the walls to be at a lower altitude than the sections on its right and left. This topographical feature proved a significant disadvantage for the city's defenders, as Ottoman guns positioned on either side of the river course were at a markedly higher altitude than the defenders in the middle.
Defense of Constantinople
On the 6th of April, the siege of Constantinople began. The Ottoman army pitched its royal tents near the central section of the land walls, facing the mightiest fortifications of the empire. Inside the city, Emperor Constantine XI made his final preparations. He was not alone — by his side stood the Genoese commander Giovanni Giustiniani Longo, a seasoned soldier of fortune, who had brought with him seven hundred well-armed men.
In fact, even before Sultan Mehmed appeared with his army before the land walls, a decision had already been made on how to organize the city’s defense. According to this plan, the great stretch of the Theodosian Walls was divided among Byzantine, Venetian, and Genoese nobles. The most critical sector — the Romanos Gate (today’s Topkapı Gate) and the Mesoteichion, the central stretch most vulnerable to attack — was entrusted to Emperor Constantine himself and Giustiniani with his Genoese troops.
The sea walls, weaker than the land walls, were left to various other commanders: Byzantine aristocrats, the Ottoman pretender Prince Orhan with his supporters, and even the papal legate Cardinal Isidore with his Latin soldiers. To the north, the defense of the Golden Horn was placed under the command of Lukas Notaras, the Megas Doux, the empire’s “grand admiral” and the emperor’s right-hand man.
Thus, every section of the city was assigned defenders — Byzantines and Latins standing side by side on the ancient ramparts. They were outnumbered, but they hoped the walls that had withstood centuries of siege would again hold firm.
The Miners
Alongside the heavy artillery, the Ottomans also used miners (sappers) during the siege. Their task was to dig tunnels under the land walls, prop them up with wooden beams, and then collapse them by fire or explosives so that the masonry above would give way.
The Byzantines responded with counter-mining. Defenders inside the city tried to detect Ottoman tunnels by listening for digging sounds through the earth. When they located one, they dug their own tunnels to intercept. Underground encounters were often deadly — fires were lit to drive the enemy out, and close combat sometimes took place in the darkness.
Although the Ottomans managed to weaken parts of the walls, many of their tunnels were discovered and destroyed. The defenders proved surprisingly effective at neutralizing this threat, forcing Mehmed to rely more heavily on his artillery bombardment.
Interested in travelling in past! Join us on a guided tour to the Walls of Constantinople and hear the stones talk!
Comments