Sack of Constantinople (1204): The Fourth Crusade's Betrayal

The Sack of Constantinople took place in April 1204, when the army of the Fourth Crusade, together with the fleet of Venice, stormed the capital of the Byzantine Empire and plundered it for three days. Launched to recover Jerusalem, the crusade ended by destroying the greatest Christian city of its time. The sack broke the Byzantine Empire into pieces and left a lasting wound between the Catholic West and the Orthodox East.

Background: a crusade in debt

Pope Innocent III called a new crusade in 1198 to recover Jerusalem, lost to Saladin in 1187. The leaders, mainly nobles from northern France, Flanders and Italy, planned to attack Egypt, the centre of Ayyubid power, by sea.

In 1201 their envoys signed a treaty with Venice. The republic would build ships and transport 33,500 men and 4,500 horses for 85,000 silver marks, and would join the expedition in return for half of any conquests. The figures were far too optimistic. When the army gathered at Venice in summer 1202, only about a third of the expected men arrived, perhaps 11,000-12,000, and they could not pay.

Doge Enrico Dandolo, then in his nineties and almost blind, offered a deal. The crusaders could postpone the debt if they helped Venice recover Zara (modern Zadar), a Christian city on the Dalmatian coast that had rebelled and placed itself under the King of Hungary. Zara was taken in November 1202. Innocent III, furious that crusaders had attacked fellow Catholics, excommunicated them, though he soon lifted the penalty from the non-Venetians.

The diversion to Constantinople

While the army wintered at Zara, a new offer arrived. Alexios Angelos, son of the Byzantine emperor Isaac II, had escaped to the West after his uncle, Alexios III, deposed and blinded Isaac in 1195. Alexios promised that if the crusaders restored his father, he would pay them 200,000 marks, provide 10,000 soldiers for the crusade, maintain 500 knights in the Holy Land, and bring the Greek Church under the authority of Rome.

The leader of the crusade, Boniface of Montferrat, and Dandolo supported the plan. Many crusaders objected and some left, but the majority sailed east. Historians still debate whether the diversion was a deliberate Venetian plot, as some once argued, or a series of improvised decisions forced by debt. Most modern scholars, such as Donald Queller and Thomas Madden, favour the second view.

The German king Philip of Swabia, who was married to Alexios’s sister Irene, also backed the scheme, and Boniface had close ties to his court. For the ordinary crusaders the argument that won the day was practical: without money and supplies the expedition would collapse, and a friendly emperor in Constantinople seemed the only way to reach the Holy Land at all.

The first siege, 1203

The fleet reached Constantinople in June 1203. On 17 July the Venetians took part of the sea walls along the Golden Horn, while the crusaders attacked by land. That night Alexios III fled with part of the treasury. The Byzantines brought blind Isaac II out of prison, and on 1 August 1203 his son was crowned co-emperor as Alexios IV.

The new emperor could not keep his promises. The treasury was empty, and melting down church silver made him hated in the city. Tension between Latins and Greeks grew. In August 1203 a group of westerners started a fire that burned through a large part of the city.

In January 1204 a palace official, Alexios Doukas, nicknamed Mourtzouphlos, seized power. Alexios IV was strangled in prison in early February, and Isaac II died around the same time. The new emperor, Alexios V, refused to pay the crusaders anything.

What happened in April 1204

In March 1204 the crusaders and Venetians signed an agreement on how to divide the city’s wealth and the empire itself after a conquest. Their clergy told them the war was just because the Greeks were schismatics and had murdered their rightful lord.

A first assault on 9 April failed. On 12 April the attackers used ships fitted with flying bridges to reach the towers of the sea walls along the Golden Horn. A small party got through a walled-up gate, and the defence collapsed. Alexios V fled that night. On the morning of 13 April the city lay open.

For about three days the army looted Constantinople. Churches, monasteries, palaces and homes were stripped. In Hagia Sophia, the great cathedral of the Orthodox world, soldiers smashed the altar to take its silver and led mules inside to carry off treasure. The Byzantine historian Niketas Choniates, who escaped with his family, described murders, rapes and the desecration of sacred objects, and wrote that the Muslims had shown more mercy when they took Jerusalem in 1187.

The crusader chronicler Geoffrey of Villehardouin, one of the leaders, boasted that never since the creation of the world had so much booty been won in a single city. Ancient bronze statues were melted down for coin. The number of people killed is not known; contemporary accounts give no reliable total.

The looting followed rules agreed in advance only in part. Valuables were supposed to be brought to three churches for an orderly division, but much was hidden by individual soldiers. Relics, from fragments of the True Cross to the supposed head of John the Baptist, were especially prized and were shipped to abbeys and cathedrals across the West. Many Byzantine nobles and clergy fled the city with whatever they could carry.

Key people

• Enrico Dandolo: Doge of Venice from 1192, who guided the crusade to serve Venetian interests; he died in Constantinople in 1205 and was buried in Hagia Sophia.
• Boniface of Montferrat: leader of the crusade, later King of Thessalonica.
• Alexios IV Angelos: the young prince whose offer diverted the crusade, emperor from August 1203 until his murder in 1204.
• Alexios V Doukas (Mourtzouphlos): the last emperor before the sack, later captured and executed by the crusaders.
• Baldwin of Flanders: elected first Latin emperor on 9 May 1204.
• Niketas Choniates: Byzantine statesman and historian, the main eyewitness on the Byzantine side.

Consequences: the Latin Empire and the Byzantine exiles

Baldwin of Flanders was crowned emperor in Hagia Sophia on 16 May 1204. Venice received “a quarter and a half of a quarter” of the empire, including key ports and islands such as Crete, and a Venetian, Thomas Morosini, became the first Latin patriarch. Crusader lords carved out states in Greece, including the Kingdom of Thessalonica, the Principality of Achaea and the Duchy of Athens.

The Latin Empire was weak from the start. On 14 April 1205 Tsar Kaloyan of Bulgaria, whose state had arisen from the Uprising of Asen and Peter, crushed the Latins at Adrianople and captured Baldwin, who died in captivity.

Byzantine resistance gathered in three successor states: the Empire of Nicaea in western Anatolia under Theodore I Laskaris, the Despotate of Epirus in western Greece, and the Empire of Trebizond on the Black Sea, founded weeks before the sack. Nicaea proved strongest. In July 1261 a Nicaean force under the general Alexios Strategopoulos retook the city for Emperor Michael VIII Palaiologos, an event described in the Recapture of Constantinople.

By the numbers

Legacy

The restored Byzantine Empire after 1261 was a smaller, poorer state that never regained its former strength. Many historians see 1204, rather than 1453, as the decisive blow: it destroyed the wealth and unity that had made Constantinople a barrier against invaders from the east. The city’s final fall to the Ottomans came in 1453, as told in the Fall of Constantinople.

The sack also hardened the split between the Catholic and Orthodox churches, formally divided since 1054. For many Orthodox Christians, 1204 became the defining memory of Western aggression. Pope John Paul II expressed regret for the events in 2001 and again in 2004, the 800th anniversary.

Treasures from 1204 still fill Western collections. The four bronze horses of St Mark’s in Venice, the Treasury of St Mark’s and many relics in French and Italian churches came from the looted city.

Myths and facts

• Myth: Venice planned the diversion from the beginning. There is no firm evidence of a secret plan; most historians now explain the attack through debt, opportunism and a chain of bad decisions.
• Myth: The Pope ordered the attack. Innocent III repeatedly forbade attacks on Christians and condemned the sack, though he later accepted its results.
• Fact: Constantinople had never before been taken by storm by a foreign army. Its walls had held off every earlier foreign besieger since the city’s dedication as capital in 330.

Timeline

• 1198, August: Innocent III proclaims the Fourth Crusade.
• 1201, April: The Treaty of Venice sets the terms for transporting the crusade.
• 1202, November: The crusaders and Venetians capture Zara.
• 1203, 17 July: First attack on Constantinople; Alexios III flees.
• 1203, 1 August: Alexios IV is crowned co-emperor with Isaac II.
• 1204, February: Alexios IV is murdered; Alexios V takes power.
• 1204, 9 April: The first assault on the sea walls fails.
• 1204, 12-15 April: The city falls and is sacked.
• 1204, 16 May: Baldwin of Flanders is crowned Latin emperor.
• 1261, 25 July: Nicaean forces recapture Constantinople.

Why it matters

The Sack of Constantinople showed how a holy war could turn against fellow Christians. It shattered the Byzantine Empire, enriched Venice, sharpened the divide between East and West, and helped clear the way for the Ottoman rise two centuries later.