It was clear that the crusaders were going nowhere fast, so one of the leaders, Boniface of Montferrat, visited his cousin Phillip of Swabia in what is now the Czech Republic. There, Boniface met Phillip's brother-in-law, Alexios, the son of the recently deposed Byzantine Emperor, Isaac II. Isaac had been forced off the throne by his brother, Alexios III. Prince Alexios saw Boniface as the head of a large and currently unemployed army, and offered Boniface a deal. If Boniface would help him get the Byzantine throne, Alexios would (1) pay 100,000 silver marks, (2) have the Orthodox Church submit to the pope and (3) have the Byzantine army join the crusade.

Boniface hurried back to Venice, where he had little difficulty in persuading the rest of the crusader leaders in going along with this. Pope Innocent heard about it and told the crusaders telling them not to attack their fellow Christians in Constantinople. However, Innocent's letter was suppressed, and the crusaders set off.