(A.D. 1201) Pope Innocent III(c. A.D. 1160–1216) Innocent III was Pope from A.D. 1198 until his death in 1216. He was one of the most influential Popes in Medieval Europe. He us... calls for the Fourth Crusade, which was hijacked by the Venetians seeking to place a puppet king on the throne of the Byzantine (Eastern Roman) Empire. This Crusade ended with the Crusaders never leaving Christian territory and instead. sacking Byzantium.