The Fourth Crusade’s sudden diversion to attacking Constantinople took the city completely by surprise. Byzantine in-fighting had used many plot twists, but this was the first time a deposed prince had found a full army to rent instantly, waiting nearby. The city normally kept most of its soldiers stationed around its shrinking empire, although there was a permanent garrison. The Emperor had the Varangian Guard, too; these were Norwegians and Swedes who stayed behind after the Norwegian Crusade a century earlier.
Constantinople had been the high-tech “First World” city when Charlemagne ruled in a wooden “palace” in rough Aachen, but now his descendants had fully caught up in war technology. They too had the Greek fire recipe, and Europeans had studied Byzantine armor and weapons. The Fourth Crusade’s knights were superior fighting machines. In a skirmish outside the city, 80 knights defeated 500 Imperial soldiers. When Venetian ships landed the main force on the Anatolian side of the Strait, the knights charged. They expected the city to welcome back its rightful king!
The city actually didn’t care; Alexios’ family had just deposed the previous family, so what was another change in nominal kingship? The Crusaders set up a siege, although they could not actually encircle the huge city. The Varangian Guard bore most of the defense, beating back knights on land and a sea attack on the sea walls. Venetian sailors set a fire as they retreated, which burned 120 acres of city buildings. Prince Alexios’s uncle, the Emperor, led a sortie against the Crusaders, but his courage failed and he retreated. He slipped out of the city in shame, while the city elders deposed him and restored the blind, aging Isaac II from prison to the throne.
The casus belli was thus taken away from the Crusaders. Prince Alexios’s father was Emperor again, not himself. The Crusaders insisted on the prince’s cause, so his blind father had him co-crowned. And then the trouble started.
It turned out that now-Emperor Alexios IV could not find the sums of gold he had promised them. His deposed uncle had taken 1000 pounds of gold with him into exile, but there probably was just not as much money in Constantinople as the young prince thought. He ordered ICONS to be melted down to extract the gold and silver leaf! This move was unthinkable, and the news quickly spread through the city. It was the worst thing a new ruler could have done; previous new Emperors had paid treasury money to householders to buy support, but this one was melting down the icons their grandparents had endowed to pay foreigners!
Alexios IV begged the Crusaders not to leave him yet; he would come up with the full payment if only they’d stay for six months longer, until spring 1204. Then he took a large Crusader army to Adrianople, to try to stamp out the deposed Emperor’s (his uncle’s) foothold of power. When the Crusader army was reduced this way, the city began to riot in earnest. Constantinople’s Latin Quarter was the target, and some Latin residents died. Crusaders and Venetians attacked a mosque in retaliation, and as fighting widened, they set the city on fire again. This time, the fire burned for three days and leveled most of the city.
Things were relatively quiet for a few months after that. The Crusaders policed the city for Alexios IV, and 1204 came around, when they were to leave in April. The old blind Emperor died, and suddenly things changed rapidly. The Byzantine Senate refused to endorse the younger Emperor, electing another man instead. They arrested Alexios IV, and he quickly met his end in a dungeon, like many Emperors before him. A new Alexios V Doukas was crowned, and he took rapid, firm anti-Crusader steps of fortification.
The Crusaders began to use their siege engines on the city, and the city’s catapult battery answered back. It was now April, when the Crusaders had planned to move on to the Holy Land, and on April 9, they recognized that their assault had been defeated. Now what? And here, the local Latin bishops stepped in. They did not want the Fourth Crusade to give up, but Pope Innocent III had again ordered them to stop attacking fellow Christians. This papal order was kept quiet. Instead, the Latin priests told the Crusaders that the Greeks were murderers and traitors, and God wanted them to stay and finish the Greeks off.
The Crusaders and Venetians began another full-scale assault, and this time they succeeded. Ships got close to the walls, and some walls were pulled down. Another fire ravaged the parts of the city still standing. On April 13, the city gates were opened.
This second time the Fourth Crusaders entered Constantinople, they were not there to put Prince Alexios on the throne, so they acted as complete enemies. They also had had months to look the city over, so they knew where to loot. They felt they were owed at least 100,000 silver marks and helped themselves. Some historians estimate that they probably took nine times that much, mostly from churches and private homes.
During this Sack of Constantinople, many priceless works of art went missing. Venetians generally took things back to Venice, but the Northern Europeans tended to just smash things. Venice also kidnapped many artisans who had trade secrets they could use. Venice’s pre-eminence in glassmaking dates from the Fourth Crusade; they installed the captured artisans on an island and kept it closely guarded. It became a sort of prison-workshop.
When the Crusader rampage was over, the city was in ruins. Much of it had burnt in the three Crusader fires, and many citizens had died in the riots and looting. The mother church of Hagia Sophia was deliberately desecrated. They smashed its art, ruined its books, seated a prostitute on the Patriarch’s Throne, and got drunk using the silver chalices as cups.
The Pope was beside himself with grief and fury at how his beloved Fourth Crusade had turned out. He rebuked and excommunicated, but the Vatican also accepted gifts from the Venetians, things they had looted from Constantinople. Pope Innocent recognized that the Crusaders had just put an end, forever, to hopes that the Western and Eastern churches could reunite.
And now they had a burnt, ruined city full of corpses that needed to be governed.