Where things stood in 1453
By the spring of 1453, the Byzantine Empire had been reduced to the city of Constantinople and a few scattered territories, mostly in southern Greece. The Ottomans controlled the land around the city on both sides of the straits. In 1452 the young sultan, Mehmed II, had ordered a fortress built on the European shore of the Bosporus, at its narrowest point, to control shipping. It was later known as Rumeli Hisari. That move made clear that he intended to take the city, and it cut off easy help from the Black Sea.
The emperor, Constantine XI Palaiologos, had appealed to the West for help. The pope and some Italian states responded with limited aid, but no large relief army came. The Byzantines also had to contend with divisions at home over the union of the Eastern and Western churches, which many Orthodox Christians disliked.
The defenses
Constantinople occupied a triangular peninsula. Water protected two sides: the Sea of Marmara to the south and the harbor inlet known as the Golden Horn to the north. On the landward side the city was guarded by the Theodosian Walls, a system built in the fifth century, which included a moat, an outer wall and a taller inner wall with many towers. These had held against many earlier attacks.
At the entrance to the Golden Horn the defenders stretched a large chain across the water, supported by floating timbers, to keep enemy ships out. It was one of the city’s key advantages.
The garrison was very small compared with the city’s size and the length of its walls. The commonly cited figure is around seven thousand fighters, including foreign volunteers, though sources differ. A contingent of Genoese soldiers under the commander Giovanni Giustiniani Longo, who arrived with a small force in January, was especially valued. Venetians living in the city and various other foreigners also took part. The defenders had to spread out thinly along a very long perimeter, and this weakness proved important.
The Ottoman forces
The Ottoman army was many times larger. Estimates in the sources vary a great deal, and later writers often inflated figures, but most historians agree the besiegers outnumbered the defenders by a wide margin. The force included regular troops, among them the sultan’s elite infantry known as janissaries, and irregular fighters, as well as a fleet.
Mehmed also put his hopes in artillery. A foundry engineer, usually named in the sources as Urban, a man from central Europe who had first offered his services to the Byzantines, built giant cannons for the sultan. The largest of them was reportedly very difficult to move and slow to reload, so it could fire only a few times a day. Even so, the sustained bombardment weakened sections of the old walls. These guns are one reason the siege is often treated as a landmark in the history of siege warfare, replacing the older trebuchets and catapults, though the walls were not simply flattened, and the defenders repaired damage overnight with timber and earth.
The siege day by day
The Ottoman army arrived before the walls in early April 1453, and the main siege is usually dated from about April 6. Over the next weeks, there were several phases:
- Bombardment and early assaults. The cannons pounded the land walls, and attacks were driven back with serious losses to the attackers.
- The naval clash. In mid-April a small group of Christian ships forced its way through the Ottoman fleet and into the Golden Horn, which boosted the defenders’ morale.
- Ships over land. Late in April, the Ottomans dragged a number of ships overland on greased tracks and launched them into the Golden Horn behind the chain. This forced the defenders to guard the sea walls along the harbor as well, stretching them even thinner.
- Mines and counter-mines. The Ottomans dug tunnels under the walls, but the defenders were able to detect and counter many of them.
By late May, supplies were short, hope of foreign help had faded, and the sultan prepared a final assault.
The final assault
The main attack began in the early hours of May 29, 1453. It came in waves: first irregular troops, then regular units, and finally the janissaries. The fighting concentrated on the stretch of walls where the cannon had done most damage. Giustiniani was wounded during the fighting and left his post, and accounts differ on how much this affected morale. At some point the Ottomans got inside the walls, and the defense collapsed.
Emperor Constantine XI is generally believed to have died fighting, although his exact fate is not recorded with certainty. The city was then sacked, as was customary for a city that had refused to surrender, and many residents were killed or enslaved. After a few days Mehmed ordered the looting to stop and began to resettle and rebuild the city. It became the Ottoman capital, later known as Istanbul.
Why it mattered
The fall of Constantinople ended the long history of the eastern Roman state, and it gave the Ottomans a capital and a commanding position between Europe and Asia. Whether it was truly a turning point for the world is a different question, since historians treat 1453 as a convenient marker rather than a sharp break.