Fourth Crusade
The Battle for Constantinople
On July 5, 1203, the Venetians were able to break the great chain that blocked the harbor, enabling the Crusaders to attack the city from both land and sea. The Franks drew up near the Blachernae palace, which lies close to the Golden Horn, while the Venetians prepared to attack from the harbor side. They built platforms in the spars of ships and put catapults on the decks.
On July 17 the Crusaders attacked in force. Defending the land side was the Varangian Guard, the Imperial palace guard that was made up of English and Danish mercenaries, and they were able to repulse the Franks. But the Venetians, led by Enrico Dandolo himself (who was at least in his 80s) were able to land on the narrow beaches and reached the top with scaling ladders. They took possession of a number of towers, descended into the city and set fire to part of it.
Meantime, Alexius had a assembled a large army for a counter-attack against the Franks. For some reason, however, his nerve failed him and he never made the attack. The Venetians in the meantime withdrew from the section of wall they had held, for they could not keep it without a victory on the Frankish side as well. Despite the fact that the Crusader assault had only partially succeeded, that night Alexius grabbed what wealth he could and fled the city with his daughter.
Those who remained in the palace thought quickly, then brought Isaac II Angelus out from his prison cell. They then turned to the Latins and declared that since Isaac was the rightful ruler, there was no need for anyone to fight on behalf of the young prince. The Crusaders countered that they would accept Isaac if his son were named co-Emperor. It was agreed, and Alexius was crowned August 1, 1203.