Final answer:
Conrad of Montferrat held the city of Tyre after the Third Crusade, and the Fourth Crusade was called for by Pope Innocent III to recapture the Holy Land, attempting a new strategy through Egypt.
Step-by-step explanation:
Conrad of Montferrat held the city of Tyre after the Third Crusade. During that period, the crusaders only maintained control over Tyre, Acre, and a few other fortresses in the Holy Land. Pope Innocent III called for a Fourth Crusade, aiming to conquer the Holy Land through Egypt and persuade the eastern churches to accept papal sovereignty. However, the crusades leading up to this had failed to reclaim Jerusalem. Breaking from previous strategies, Frederick later landed in Acre, the main port still under Christian control, but his slow progress had detrimental effects due to his excommunication.