It was led by several leaders, Frankish and Venetian. The purpose was to put Alexios IV on the throne, who was a Byzantine prince in exile. In return for giving him the Byzantine throne, Alexios IV promised money and men to help in the crusade. He tried to live up to his promises, but that made the Greeks unhappy. He was killed in a coup, and the new emperor didn't want to help the crusader army. So the crusaders attacked the city and plundered it. The Venetians got a part of the city and some parts of the Byzantine empire, so that they had an unbroken chain of ports towards the Black Sea. Baldwin I of Flanders became the Byzantine emperor.