The Fourth Crusade was an armed expedition by western European Crusaders to reclaim Jerusalem, which was under the control of the Muslims at the time. Despite this stated aim, a series of economic and political events instead led to the sacking and capture of Constantinople, the capital of the Byzantine Empire. Thus, when the Fourth Crusade began, the crusaders needed transport aboard Venice's ships. The city's Doge Enrico Dandolo agreed to transport the Crusaders, on the condition that they take the Dalmatian city of Zadar and recapture Constantinople. As the crusaders took Constantinople, the Venetian fleet sacked it and stole four bronze horses, among other things. The horses were later used as ornaments on the Basilica di San Marco.
Prior to the city's sacking, the Mentor of the Levantine Assassins, Altaïr Ibn-La'Ahad, had hoped to spread the Assassin ideology to the Byzantine Empire, but was forced to cut his stay in Constantinople short to return to Masyaf.
- Assassin's Creed II (mentioned in Database entry only)
- Assassin's Creed: Renaissance (mentioned only)
- Assassin's Creed: The Secret Crusade (mentioned only)