Dandolo's first important political roles took place during the crisis years of 1171 and 1172, which were a tumultuous period between the Byzantine and Venetian empires. After Byzantine emperor Manuel Comnenus restored Pisans and Genoans, both enemies of the Venetians, to their quarters in Constantinople as part of his plan to reclaim Italy, an angry Venetian mob attacked the recently reinstated Genoese quarter. This attack caused Comnenus in March 1171 to order the seizure of goods and imprisonment of thousands of Venetians living in the empire. Popular Venetian anger with the attack forced Doge Vitale II Michiel to gather a retaliatory expedition, which included Dandolo. This expedition fell apart when its participants were struck by plague in 1172, and upon his return Michiel was killed by a mob of Venetians, angry with his defeat.