Overview
The siege of Constantinople in 1203 was a Crusader siege of the capital of the Byzantine Empire, in support of the deposed emperor Isaac II Angelos and his son Alexios IV Angelos. It marked the main outcome of the Fourth Crusade.
Siege
To take the city by force, the Crusaders first needed to cross the Bosphorus. About 200 ships, horse transports and galleys would undertake to deliver the crusading army across the narrow strait, where Alexios III had lined up the Byzantine army in battle formation along the shore, north of the suburb of Galata. The Crusaders' knights charged straight out of the horse transports, and the Byzantine army fled south.
The Crusaders followed south, and attacked the Tower of Galata, which held one end of the chain that blocked access to the Golden Horn. The Tower of Galata held a garrison of mercenary troops of English, Danish, and Italian origin. As the crusaders laid siege to the Tower, the defenders routinely attempted to sally out with some limited success, but often suffered bloody losses. On one occasion the defenders sallied out but were unable to retreat back to the safety of the tower in time, the Crusader forces viciously counterattacked, with most of the defenders being cut down or drowning in the Bosporus in their attempts to escape. The Golden Horn now lay open to the Crusaders, and the Venetian fleet entered.
On 11 July the Crusaders took positions opposite the Blachernae palace on the northwest corner of the city. Alexios IV was paraded outside the walls, but the citizens were apathetic, as Alexios III, though a usurper and illegitimate in the eyes of the westerners, was an acceptable emperor for the Byzantine citizens. The siege began in earnest on 17 July, with four divisions attacking the land walls, while the Venetian fleet attacked the sea walls from the Golden Horn. The Venetians took a section of the wall of about 25 towers, while the Varangian Guard held off the Crusaders on the land wall. The Varangians shifted to meet the new threat, and the Venetians retreated under the screen of fire. The fire lasted for 3 days and destroyed about of the city, leaving 20,000 people homeless.
Alexios III finally took offensive action, and led 17 divisions from the St. Romanus Gate, vastly outnumbering the Crusaders.
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