The Fourth Crusade was proclaimed by Pope Innocent III in 1198 to recover Jerusalem — and it never got there. Unable to pay Venice for its fleet, the army was turned first against the Christian city of Zara and then, by a bargain with the claimant Alexios IV, against Constantinople. In April 1204 a Latin Christian army stormed and sacked the greatest city in Christendom: three days of massacre, rape, and plunder.

This is the event the Orthodox cannot forget, and the facts carry the indictment. The crusaders desecrated Hagia Sophia itself — smashing the great altar and dividing it as loot, leading mules and asses into the sanctuary to carry off the silver, pouring the consecrated Body and Blood onto the floor, and (per the eyewitness Niketas Choniates) seating a drunken harlot on the patriarch’s seat to sing and dance. They installed a Latin emperor and a Latin patriarch by force and held the City for fifty-seven years (the Latin Empire, 1204–1261); the relics and treasure were carried west, and largely never returned. Choniates’ bitter verdict is the one the East never forgot — that the Saracens, when they had taken Jerusalem, dealt more mercifully than these men who wore the cross of Christ.

The schism became unbridgeable in the streets, not the schools. Photius and the Filioque had been an argument among theologians; 1204 was a wound in the body. After the sack, “union with Rome” no longer meant a disputed clause in the Creed — it meant the memory of Latin soldiers butchering Greek Christians in their own cathedral. And many historians (Steven Runciman among them, who called it a greater crime against humanity than any) judge that the catastrophe of 1204 so shattered Byzantium that it helped deliver the City to the Ottomans two and a half centuries later.

The Catholic answer makes no excuse; owning the crime is the only honest reply. The Crusade was a betrayal of its own purpose: hijacked by debt and ambition, it was the negation of a crusade, not the act of one. And it was carried out in direct defiance of the Pope who called it — Innocent III had forbidden the attack on Christians and excommunicated the army after Zara. When the reports of the sack reached him, he condemned the crusaders without restraint: their swords, meant for the infidel, were “now dripping with Christian blood”; they had “spared neither age nor sex”; they had stripped the silver from the very altars. The Church owns this as a grievous sin — condemned by the Pope when it happened, and formally repented of by the popes since.