How the Fourth Crusade Was Aimed at Jerusalem but Hit Constantinople

The 4th Crusade aimed to retake Jerusalem. It was well-financed and had Papal backing. So how did it end up sacking a fellow Christian city, the Byzantine Empire’s capital Constantinople?

Feb 22, 2022By Matthew Doherty, Msc East Asian Relations, BA Asia Pacific Studies

fourth crusade conquered zara


On October 9th, 1192, King of England Richard I departed the holy land, effectively ending the 3rd Crusade and dashing any hopes of a Christian conquest of Jerusalem. It took six years and the election of a new pope in 1198 for a 4th Crusade to be commissioned, this time bound for Egypt. It was hoped that Egypt could then be ransomed for the return of Jerusalem. But the crusade never achieved any of this; instead ending in the rapacious looting of the Byzantine Empire’s capital of Constantinople in April 1204.


The 4th Crusade Forms

morgan bible picture
Leaf from the Morgan Picture Bible, c. 1250, via Digitized Medieval Manuscripts


Upon coming to office, Pope Innocent III immediately had ambitions to recapture Jerusalem and restore Christian fortunes in the Levant. This was to be a pan-European movement; old scores between nobles and knights were to be put aside. He commanded: “Let all, collectively and individually, prepare themselves.”


Richard’s 3rd Crusade had secured Christian control over the coastal cities of the holy land, but their position, surrounded by Muslim forces, was precarious. Innocent gave the usual papal blessing, as well as an edict allowing the remission of sin for anyone who took the cross.


The medieval knight was a man of violence. And violent men, it was said, would find it very hard to enter the gates of heaven. Religiously-minded crusaders craved remission of sin. But the practical among them knew armed pilgrimage to the Near East was an opportunity to acquire new lands and plunder – all sanctified by the will of God’s sole earthly representative.

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With news of Innocent’s call, a huge wave of optimism filled Europe. One knight summed up the feeling of the times: “we wish only to avenge the honour of Jesus Christ and, by the grace of God, reconquer Jerusalem.”


Thibaut, Count of Champagne, was elected to lead the army, despite being aged only 22. However, he was already a successful knight; one chronicler stated, “no other man at that time had so many devoted followers.” It is perhaps a testament to Thibaut’s popularity that older men (such as Louis of Blois and Baldwin of Flanders) were willing to fight and potentially die under his command.


So why did the 4th Crusade fail so spectacularly? How did a well-financed, well-led band of experienced soldiers end up 1000 kilometers from their objective, sacking a fellow Christian city?


The First Diversion: Deal With the Devil

fourth crusade enrico dandolo
Portrait of Enrico Dandolo by Tintoretto, 13th Century, via World History Encyclopedia


Most of the previous crusades had involved marching slow masses of soldiers across hostile lands to reach Palestine. The 4th Crusade would be different. Its objective was Egypt and would require the use of a large fleet of ships to reach it.


Only two seafaring nations in Southern Europe were able to muster such a flotilla, Genoa and Venice. Genoa was uninterested in the scheme, but the Venetians agreed to provide a naval force capable of transporting, according to the French knight Villehardouin, “four thousand five hundred horses and nine thousand squires… four thousand five hundred knights and twenty thousand foot soldiers.”


This totaled 33,500 men. Such a gigantic force would need to pay for its transportation, as the Venetians could not foot the bill alone. For such a fleet to be built, the Venetians would have to suspend their other lucrative trading interests in the region.


This was not a decision taken lightly; as a Venetian Doge remarked, “a request of this magnitude requires careful consideration.”


That Doge was Enrico Dandolo. He was around ninety years old and as shrewd a political operator as they came. Dandolo had seen it all and done it all: soldier, statesman, admiral, merchant. For years he had expanded the interests of Venice through conflict with the Byzantine Empire. The crusade offered him and his people an opportunity to make some serious money, as well as get in the Pope’s good books.


It was plain that this deal was the only viable option for the crusaders. It also left them with a massive bill owed to the Venetians.


The Second Diversion: An Untimely Death

medieval deathbead art
Medieval deathbed. Miniature taken from the manuscript Le desert de la religion, British Library Collection, via Medievalists


Then came the Crusade’s first great disaster.


Count Thibaut, the great hope of Catholic Europe, died suddenly and unexpectedly from a fever. The crusade was left leaderless.


As the Christian host gathered around Venice in the summer of 1202, it became clear that “only a quarter of the knights and half the infantry” had materialized, leaving a force of perhaps 12,000. The lack of troops is explained by the death of the Thibaut.


Count Boniface of Montferrat was eventually elected to lead the army, but he was an Italian. Though he had a good crusading pedigree, the soldiers making up the 4th Crusade were mainly drawn from France and would have preferred it if Thibaut had survived to lead them. A great many had simply not turned up.


The crusaders gathered at Venice were now left in serious debt, as it had previously been agreed that each man would pay his own share for the passage. There can be little doubt that Dandolo used the crusaders’ predicament to his own advantage, but under the circumstances, he could do little else. The size of the Venetian commitment to the 4th Crusade was immense, unparalleled in the history of Italian maritime republics. Assembling this fleet had drained the Venetian treasury, and when it became apparent the army could not pay in full, Dandolo was left with little option but to recoup his losses in some fashion.


The Third Diversion: Zara

crusaders conquering zara
The Crusaders Conquering the City of Zara in 1202 by Andrea Vicentino, 16th century, via Archivo Historia


The crusading army of 1202 comprised a large, battle-hardened body of mostly professional European soldiery. For Dandolo, the need to use it to further Venetian interests proved too great, and it was agreed that the debt the crusaders owed would be put on hold if they helped take the Dalmatian port of Zara, a Christian city in the Byzantine Empire. The booty gained from the conquest would then be used to pay the Venetians off, and the fleet would then sail to Egypt without delay.


Reluctantly, most of the crusaders agreed. The time of year also conspired to force the crusade down this path as Egypt, the objective, was out of reach until the spring. The debt to the Venetians could not just be ignored, as their fleet was still a crucial part of the venture. Nor could Dandolo afford to pursue any other course of action – for him, time was money. He had the army with him now and could not afford to wait until the next campaigning season in Egypt for fear the crusade might break up. He and his people would have poured their money into the scheme for nothing.


Villehardouin gives us a description of the capture:


“On the seaward side they hoisted scaling ladders from the warships. [Siege engines] began stoning the walls and towers. The battle lasted five days, when the sappers were ordered to dismantle the walls. The inhabitants finally gave way….”


Upon taking the Dalmatian port in December 1202, it was found that the plunder gathered proved insufficient. The Venetians were still owed money; hence the 4th crusaders were still required to fulfill obligations to their allies.


The Fourth Diversion: The Pretender to the Byzantine Empire

boniface proclaims crusade
Boniface II, marquis de Montferrat by Henri Decaisne, 1847, via Réunion des Musées Nationaux – Grand Palais


Just days after the taking of Zara, Boniface of Montferrat arrived in the crusader camp with a startling proposition. He had brought a man named Alexius Angelos, a rival claimant for the Byzantine throne, currently held by Isaac II.


In return for deposing the current emperor in favor of himself, Angelos agreed to pay off the crusader debt with the Venetians and finance an assault on the holy land after he was placed in power. Most surprising of all, he also agreed to offer the crusaders union of the Greek Orthodox Church with Rome.


If the plan succeeded, everyone would benefit. The Venetians would finally be paid off, leaving crusader honor intact, the Pope would be ecstatic that the schism of Eastern and Western Christianity could be unified under his control, and the crusaders themselves would be able to fulfill their holy vows by mounting a gargantuan assault on the Islamic world.


The mass of the army was already quartered in Zara, a perfect start point for an overland march through the Balkans to capture the Byzantine capital of Constantinople. During the winter, news also reached the crusader camp that another ruler had deposed Isaac II, who called himself Alexius III. There were clearly internal troubles within the Byzantine Empire – something the 4th crusaders and their Venetian allies were only too willing to exploit.


venetians at constantinople
Assault of the Crusaders on Constantinople 1204 by David Aubert, 15th Century, via akg-images


In early July, the crusader host established a camp outside the city. When Alexius Angelos was paraded in front of the walls, none of the watching citizens seemed to even know who he was. The crusaders were confronted by the fact that they would need to use force to get their man on the throne.


On the 17th, they mounted a series of vicious assaults, which left the place in flames. Alexius III, a less-than-adequate military commander, fled the city. On 1st August, Alexius Angelos was crowned as Alexius IV, ruling as co-Emperor with Isaac II (who had been imprisoned and blinded by Alexius III). This dual monarchy was set up to preserve the myth of Byzantine imperial integrity.


Alexius IV’s first act was to issue a decree to pay the Venetians 100,000 marks (the balance of crusader debt). However, the new Emperor could not satisfy the crusader’s demands without totally alienating his own people.


Public opinion soon turned against him as accusations of homosexuality were leveled. According to Choniates, a Greek chronicler at the time, people claimed: “that he kept company with depraved men.” Eventually, Alexius was overthrown by his son-in-law, who unsurprisingly refused to honor the treaty with the Christians. Moreover, the supply situation in the crusader camp was growing desperate as their position ensured they controlled no fertile provinces for easy forage.


Unhappy with the Byzantine diversion, some of the army left for the holy land under their own initiative. As Villehardouin stated, any course of action seemed preferable to seeing the army “broken up and destroyed.”


Months went by without action. The Byzantine Empire’s inter-factional politics became interminable for the crusaders. The situation grew ever more uneasy, so the crusade leaders made the pragmatic and desperate decision to sack Constantinople.


The Sack of Constantinople & Aftermath of the 4th Crusade

sacking of constantinople
The Taking of Constantinople by Jacopo Palma il Giovani, c. 1587, via Doge’s Palace, Venice, through Google Arts & Culture


On 9th April 1204, crusader attacks began along the city’s northern shore, the Venetian ships having been converted into floating siege towers.


Initial assaults were repulsed, but three days later, two knights managed to scramble onto the walls. The first was hacked to pieces by the Varangian Guard. The second, Andrew of Orboise, confronted the defenders who, according to Villehardouin, “rushed at him with axes and swords and rained blows on him, but, by God’s grace, he was wearing armour and they did not wound him. He was protected by God, and it was not His will that the rule of the [Byzantine’s] should endure.”


Before evening, a section of the city was in the crusaders’ power. Fearing a counterattack from the Byzantines, the crusaders then set fire to a number of houses, the flames engulfing a large part of Constantinople. That night, the Byzantine commander fled along with most of his surviving troops.


Three days of violence and systematic plunder followed, the crusade leaders ordering their personal retinues to “seize possession of all the best and richest houses of the city.”


The looting army stole approximately 500,000 marks, enough to fund a large European state for ten years. Boatloads of holy relics were also taken, as well as the famous Horses of Saint Mark statue, which is kept in Venice even today.


In the aftermath, a new Crusader State was established, the short-lived Latin Empire. In reality, the only thing the 4th Crusade achieved was to hasten the final collapse of the Byzantine Empire.


Innocent was shocked when he heard of the bloodshed, condemning the whole venture:


“For they who are supposed to serve Christ rather than themselves, who should have used their swords against the infidel, have bathed those swords in the blood of Christians.”

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By Matthew DohertyMsc East Asian Relations, BA Asia Pacific StudiesMatthew is a writer, editor, and teacher, specializing in all things military history related. His work has been published in the UK Defence Journal and the Small Wars Journal. He holds an Msc from the University of Edinburgh and a BA from the University of Leeds. In his spare time, he also writes science fiction stories.