From the moment it sailed, the Fourth Crusade was dominated by the commercial and political imperatives of the supplier of their fleet, the Doge of Venice. With the crusaders unable to pay, the Doge threatened to intern them in the harbor unless they subdued Venice’s trading competitors in the Adriatic, principally Zara in the Byzantine Empire. After brutally sacking Zara, the Crusaders, still indebted, were seduced by the promise of huge rewards from the Byzantine prince, Alexios IV Angelou, in return for deposing his brother, the emperor. Diverting to Constantinople, the crusaders accomplished their mission, and installed Alexios IV as emperor, but he was rapidly overthrown and slain. Baulked of their payment, the crusaders laid siege to the city and captured it, massacring the inhabitants, and desecrating its holy sites. Only a small separate force of crusaders ever reached the Holy Land, sufficient to replenish the garrisons but not to conduct any military operations.
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