The Crusader Army That Was Supposed to Invade Egypt in 1202 and Instead Sacked Constantinople in 1204 to Pay Off Its Venetian Debt

Pope Innocent III had preached the Fourth Crusade in 1198 with the strategic objective of recapturing Jerusalem (lost in 1187 to Saladin) by invading the Mamluk-controlled Egypt — the political and military centre of the Islamic Near East at the time. The amphibious nature of the planned campaign required a fleet.

In 1201 the crusader leadership — predominantly French aristocrats — signed a contract with the Republic of Venice to provide transport. The contract specified ships for 33,500 men and 4,500 horses, with an agreed price of 85,000 silver marks. Venice undertook to build the fleet by summer 1202.

What went wrong

Venice built the fleet on schedule. The crusaders did not arrive in their contracted numbers. By summer 1202 only about a third of the planned crusader force had reached the Venetian assembly point at the Lido. The crusaders could pay only 51,000 of the 85,000 marks owed.

The Venetian Doge Enrico Dandolo — at 94 the most senior Italian political figure of the period, who had a personal grievance against the Byzantine Empire that had cost him his eyesight during a younger diplomatic visit — proposed a solution. Venice would accept payment in services rather than silver. The crusader army would attack the Hungarian-controlled Adriatic port of Zara, which had recently rebelled against Venetian commercial dominance.

The proposal was theologically scandalous. Zara was a Christian Catholic city. Innocent III forbade the attack in writing. The crusader leadership consulted the papal letter and proceeded to attack Zara anyway. The city was sacked on 24 November 1202.

Innocent III excommunicated the entire crusader army (then quietly lifted the excommunication against the lay crusaders while maintaining it against the Venetians). The crusade was now technically heretical and operationally bankrupt.

The Byzantine offer

At Zara in early 1203 the crusader leadership received an offer from Alexios Angelos — the son of the deposed Byzantine emperor Isaac II, whom Alexios’s uncle Alexios III had blinded and imprisoned in 1195. Young Alexios proposed that the crusader army restore him to the Byzantine throne. In exchange he would pay 200,000 silver marks, supply 10,000 Byzantine troops for the Egyptian campaign, and bring the Eastern Orthodox Church back into communion with Rome.

The offer would more than pay off the Venetian debt and would (he claimed) make the Egyptian campaign more practicable. The crusader leadership accepted.

The army arrived at Constantinople on 24 June 1203. The city was the largest in Europe — population approximately 500,000, walls that had held off every major siege since their 5th-century construction. The crusader fleet broke through the Golden Horn sea defences in July; the assault on the land walls drove out Alexios III; young Alexios was crowned co-emperor as Alexios IV alongside his blind father Isaac II on 1 August 1203.

What Alexios IV could not pay

The promised 200,000 marks did not exist. The Byzantine treasury was empty. Alexios IV imposed heavy emergency taxation, melted down imperial gold-and-silver liturgical objects from the Hagia Sophia, and managed to pay approximately half the sum across late 1203. The remaining half was unrecoverable.

The Byzantine population reacted against Alexios IV’s tax demands and against the Latin presence in the city. A senior Byzantine official named Alexios Doukas (nicknamed Murtzuphlos for his bushy eyebrows) led a palace coup in January 1204. Alexios IV was strangled. Isaac II died within days. Doukas declared himself Alexios V.

The new emperor refused to pay the remaining debt. The crusader army camped outside the city was now stranded with no plausible return route and no payment.

12-15 April 1204

The Venetian and crusader leadership voted to take Constantinople by storm and to divide the city among themselves. The assault began on 9 April 1204 from the Golden Horn. The Venetian galleys pushed siege ladders against the sea walls; crusaders fought their way up onto the towers; a section of the walls was breached on 12 April.

The Latin army entered the city on the afternoon of 12 April 1204. The sack ran for three days.

The destruction was systematic. The Hagia Sophia was looted of every transportable liturgical object — gold communion vessels, silver altar fittings, jewelled icons, the silver-and-gold canopy over the high altar. The patriarchal throne was broken. A drunk Latin prostitute, contemporary Byzantine accounts record, was placed in the patriarch’s chair and sang bawdy songs. The Hagia Sophia’s collection of holy relics — including a portion of what was claimed to be the True Cross and the Crown of Thorns — was distributed among Catholic monastic and royal foundations across Western Europe over the subsequent decade.

The four bronze horses on the Hippodrome — Lysippan classical sculptures of approximately 250 BCE — were shipped to Venice. They have been on the façade of St Mark’s Basilica since 1254 and are the most familiar surviving piece of the sack.

The Byzantine historian Niketas Choniates — a survivor and eyewitness — estimated the civilian death toll at approximately 30,000, with extensive rape and torture of the surviving population to extract concealed wealth. The Latin contemporary Geoffrey of Villehardouin gives a lower figure but does not dispute the pattern.

The Latin Empire

A new Latin Empire of Constantinople was established by the conquering force. Baldwin IX of Flanders was elected emperor on 16 May 1204. Venice took three-eighths of the city and the most valuable Aegean trade routes. The original objective — the invasion of Egypt — was abandoned. No Fourth Crusade soldier reached Egypt.

The Latin Empire lasted 57 years. The Byzantines reconquered Constantinople on 25 July 1261 under Michael VIII Palaiologos. The Byzantine empire survived as a regional power for another 192 years before its final collapse to the Ottoman conquest of Constantinople in 1453.

The Eastern Orthodox-Catholic schism — which had been a theological-political division since 1054 but which had been intermittently reconcilable through the 11th and 12th centuries — became permanent after 1204. The sack of Constantinople by a papal-blessed Catholic army made any subsequent reconciliation politically impossible. Pope John Paul II issued a formal Vatican apology to the Eastern Orthodox communion in 2001 — 797 years after the events.