The Fall of Constantinople, 1453: Siege, Sources and Aftermath

The 1453 siege of Constantinople told step by step, from Mehmed II's preparations to the final assault, with a close look at where the eyewitness and later accounts disagree.

Avevide · Last reviewed October 24, 2026 · 9 min read

On May 29, 1453, Ottoman troops fought their way through the walls of Constantinople, and the last emperor of the Byzantine state died somewhere in the fighting. A city that had been an imperial capital since the fourth century became the capital of a different empire, and the old Roman line that had begun with Constantine came to an end.

The fall is one of the best-documented sieges of the Middle Ages, yet the documents disagree on surprisingly basic points: how long the siege lasted, how many men fought on each side, how the attackers finally got in, and how the emperor died. This deep dive tells the story of the siege and, at each step, shows what the sources say and where they part ways.

A note on the sources used here. Alongside modern summaries from the Library of Congress, the Metropolitan Museum of Art, and UNESCO, this account draws on two classic narratives that are now in the public domain: Edward Gibbon's eighteenth-century Decline and Fall of the Roman Empire and Edwin Pears's The Destruction of the Greek Empire (1903). Both worked from the contemporary chroniclers, and both reflect the assumptions of their own times.

A capital without an empire

By 1453, Constantinople was a great city with almost nothing left around it. After the Byzantines recovered it from the crusaders in 1261, the Met's essay on the period explains, the cost of rebuilding devalued the currency, the empire's territory steadily contracted, and its population shrank. The Byzantine aristocracy could not compete with the Genoese and Venetians, who controlled increasingly profitable trade routes. And the city was one of the first to lose many of its people to the Black Death in 1347.

The Met's estimates make the decline vivid: a population of between 250,000 and 1,000,000 in the fourth and fifth centuries had fallen to about 50,000 by 1453. Gibbon, writing much earlier, put the population on the eve of the siege at more than 100,000. That gap is a reminder that premodern population figures are reconstructions, not counts.

The Library of Congress's country study of Turkey adds that the city had been cut off by land since 1365 and depended on Venetian traders for supplies and reinforcement by sea. The Ottomans had long since moved their own seat of government into Europe, to Adrianople (Edirne).

Mehmed II prepares

Mehmed II, whose reigns ran from 1444 to 1446 and from 1451 to 1481, made the city his target. Pears describes how he built a fortress on the European shore of the Bosporus, begun in March 1452 and completed by the middle of August, to control traffic through the strait.

He also secured artillery. According to Pears, drawing on the chronicler Ducas, a Hungarian or Wallachian cannon founder named Urban had first offered his services to the emperor, then went over to the sultan for higher pay. He cast an enormous bombard at Adrianople, which took sixty oxen to drag toward the capital.

Inside the city, Emperor Constantine XI and many of his dignitaries were ready to accept union with the Latin Church in the hope of winning Western defenders. On December 12, 1452, a service celebrating the union was held in Hagia Sophia. Pears recounts that it caused deep offense among those who rejected union, and that the monk Gennadius, also known as George Scholarius, asked why they put their trust in Italians instead of in God, declaring that in losing their faith they would lose their city.

The city's defenses were formidable. UNESCO's description of the Historic Areas of Istanbul notes that the land wall of Theodosius II ran 6,650 meters, with a second line of defense created in 447, and was a leading model for military architecture. By sea, the harbor of the Golden Horn was closed by a chain. Pears says the chain was stretched or strengthened on April 2, 1453, from a tower near Seraglio Point to the walls of Galata.

Counting the armies

Every account agrees that the defenders were badly outnumbered. They disagree on almost everything else.

On the defenders, both Gibbon and Pears rely on George Phrantzes (also spelled Sphrantzes), a close aide of the emperor, who said Constantine ordered a census of all men able to bear arms, including monks. The total was so low that the emperor told him to keep it secret. Gibbon gives Phrantzes's figure as 4,970 Romans; Pears gives 4,983 Greeks and "scarcely two thousand foreigners." Even the same source, in other words, reaches us in slightly different forms. Pears adds that an estimate of about eight thousand defenders is "the estimate in which nearly all writers concur." Gibbon names the most important foreign commander, John Giustiniani (Justiniani in older English), a Genoese noble who brought a body of two thousand men.

The Ottoman figures range far more widely. Gibbon reports that Ducas, Chalcondyles, and Leonard of Chios put the sultan's forces at three or four hundred thousand, while Phrantzes gave 258,000. Gibbon also cites the scholar Philelphus, who had lived in Greece some thirty years earlier, as believing the sultan's forces of any value could not exceed sixty thousand horse and twenty thousand foot. In a footnote Gibbon also cited Marsigli, an earlier writer on the Ottoman military, who held that "the effective armies of the Turks are much less numerous than they appear," although Gibbon himself judged that Phrantzes's 258,000 did "not exceed the measure of experience and probability." Modern readers should treat all of these figures as estimates.

The siege, April and May 1453

The Ottoman army arrived before the walls in early April. Gibbon dates the start of the siege to April 6; Pears describes the army arriving on April 5 and taking up its position along the whole line of the walls by April 7. That small disagreement explains another: the Library of Congress calls it a fifty-day siege, while Gibbon says it lasted fifty-three days.

Ottoman artillery pounded the land walls, but the harbor chain kept the Ottoman fleet out of the Golden Horn. On April 20, according to Pears, four relief ships fought their way through the Ottoman fleet into the harbor, a humiliation that, Pears notes, "all accounts agree" roused the sultan to fury.

Mehmed's answer is the most famous episode of the siege. On the evening of April 21 or the morning of April 22, in Pears's reconstruction, between seventy and eighty vessels were hauled overland across the hills behind Galata and launched into the Golden Horn, bypassing the chain. The Library of Congress describes the ships moving "on greased runners." Gibbon, who called the operation "bold and marvellous," says the planks were greased with the fat of sheep and oxen, yet he also cautioned that the "boasted miracle" had perhaps been equaled by the engineering of his own day. Either way, the defenders now had to guard the harbor walls as well as the land walls, with men they did not have.

May 29: the final assault

The last assault came in the early hours of May 29. Two moments decided it, though the sources weigh them differently.

The first was the wounding of Giustiniani. Gibbon wrote that the immediate loss of the city "may be ascribed to the bullet, or arrow, which pierced the gauntlet of John Justiniani," whose withdrawal to seek treatment demoralized the defenders around him. Gibbon followed the harsh judgment of Phrantzes and Leonard, but his own footnotes concede that Ducas treated Giustiniani more leniently, and a later editor's note adds a Georgian account that describes the wound as more serious.

The second was a small gate. Pears tells how Ottoman soldiers found a postern called the Kerkoporta open, entered, and raised their standards on nearby towers. He is careful to add that "the entry of the Turks by the Kerkoporta is only related by Ducas," though he thought other writers indirectly confirmed it.

Then there is the emperor's death, which no one can describe with certainty. Pears states it plainly: "The manner of his death is, however, doubtful. No contemporary writer was present." Phrantzes had been sent elsewhere. Critobulus said Constantine cried out that the city was taken while he still lived, and charged into the enemy. Leonard said he was struck down by a Janissary. Ducas reported that two Turks claimed to have killed him and taken his head. What the accounts share, in Pears's summary, is testimony to his bravery: "All accounts attest his courage."

The city was then sacked. Gibbon reports that about two thousand Christians were killed in the first heat of the pursuit before, in his account, the victors turned to taking captives and plunder.

What changed, and what did not

In military terms, the Library of Congress argues, the conquest "did not have a critical effect on European security." Its significance was symbolic. Mehmed regarded himself as the successor of the Byzantine emperors and made the city his imperial capital. Hagia Sophia was converted into a mosque. The country study explains that the Ottoman name Istanbul derives from a Greek phrase, eis tin polin, meaning "to the city."

Mehmed also chose continuity in some respects. The city remained the center of the Greek Orthodox Church, and Mehmed, in the country study's words, proclaimed himself its protector and appointed a new patriarch. Pears identifies that patriarch as Gennadius, the same monk who had opposed church union, and describes him as chosen by a local synod after the sultan told the Christians to elect one.

The Met describes the decades after 1453 as a period of renewed prosperity. The harbor again became an important center of trade, the population grew, and Muslims made up an estimated three-fifths of the population by 1477, alongside Byzantine and European communities. Mehmed commissioned two palaces, including the one later known as Topkapi, and the mosque complex now called Fatih. The Met's essay on early Ottoman art calls him "one of the greatest Renaissance patrons of his time." The remaining Byzantine centers at Mistra and Trebizond fell within a few years.

Reading the fall today

The fall of Constantinople is often told as a single dramatic story. The sources show something messier. They were written by people with loyalties and grievances, such as an imperial aide and a Latin archbishop who both condemned the Genoese commander, and by chroniclers who were not present at the moments they describe. Even careful historians such as Gibbon and Pears had to choose between them.

That does not make the event unknowable. The outline is secure: a long Byzantine decline, a determined young sultan with artillery and overwhelming numbers, a desperate defense, a final assault on May 29, and the transformation of the city into an Ottoman capital. It is the human details, the numbers and the last moments, that remain open to argument.

Key takeaways

By 1453, Constantinople was a shrunken, isolated city whose population had fallen dramatically since late antiquity.
The sources broadly agree the defenders numbered under about ten thousand, but the estimates of the Ottoman forces that Gibbon reports range from about 80,000 regular troops to 400,000.
Mehmed II's overland transport of ships into the Golden Horn bypassed the harbor chain and stretched the defense.
How Constantine XI died is unknown; no surviving contemporary writer witnessed it.
Mehmed made the city his capital, converted Hagia Sophia into a mosque, and kept the Orthodox patriarchate under Ottoman protection.

Sources

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