Britannica Sources used in this answer

How did Alexius IV become Byzantine emperor with Crusader support?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Innocent III Innocent III, fresco in the Abbey of San Benedetto, Subiaco, Italy.

Alexius IV Angelus became Byzantine emperor in 1203 through a deal made with the leaders of the Fourth Crusade and their Venetian allies.21

After his father, Emperor Isaac II Angelus, was blinded and deposed by Alexius III, the young Alexius escaped and sought support from his brother-in-law, Philip of Swabia. Seeking to restore his family to the throne, Alexius offered the Crusaders significant incentives if they would divert their expedition to Constantinople to reinstate him. His promises included:21

Substantial financial payments and supplies.21
Military support for the Crusade's campaign in Egypt.21
The maintenance of 500 knights in the Holy Land.2
The submission of the Byzantine church to Rome.21

Despite explicit prohibitions from Pope Innocent III, the Crusade leaders accepted the offer to resolve their own financial difficulties. Upon arriving in Constantinople in 1203, the Crusaders attacked the city, causing Alexius III to flee, which allowed the prince to be elevated to the throne as Alexius IV alongside his father.31