During preparations for the Fifth Crusade in 1217, it was decided that Damietta should be the focus of attack. Control of Damietta meant control of the Nile, and from there the crusaders believed they would be able to conquer Egypt. From Egypt they could then attack Palestine and recapture Jerusalem. When the port was besieged and occupied by Frisian crusaders in 1219, Francis of Assisi arrived to peaceably negotiate with the Muslim ruler. The siege devastated the population of Damietta. After the crusaders captured Damietta in November 1219 they loot the city. In 1221 the Crusaders attempted to march to Cairo, but were destroyed by the combination of nature and Muslim defences.