The Battle for Egypt
The Plan of Louis IX was more or less the same as the plan for the fifth crusade. They would attack Egypt and force the Sultan to hand over Jerusalem and other areas in the Holy Land. On the 6th of June 1249 CE Damietta was taken with little resistance from the Egyptians. In November of that year Louis IX marched towards Cairo.
A force led by Robert of Artois alongside the Knights Templar and the English army, led by William Longespée, was sent out to attack the Egyptian camp at Gideila. The camp was overrun in a surprise attack. Instead of waiting there for the reinforcements of Louis IX the army advanced to Al Mansurah.
The Egyptians had opened the gates to let the Crusaders in but once inside the city the Crusaders were attacked and the army completely destroyed. Only a handful of Christian souls survived this battle.