Battle Of La Forbie
The Battle of La Forbie, also known as the Battle of Harbiyah, was fought October 17, 1244 – October 18, 1244 between the allied armies (drawn from the Kingdom of Jerusalem, the crusading orders, the breakaway Ayyubids of Damascus, Homs and Kerak) and the Egyptian army of the Ayyubid Sultan as-Salih Ayyub, reinforced with Khwarezmian mercenaries.
The papal interests represented by the Templars brought on a conflict with Egypt in 1243, and in the following year a Khwarezmian force summoned by the latter stormed Jerusalem. The crusaders were drawn into battle at La Forbie in Gaza. The crusader army and its Bedouin mercenaries were completely defeated within forty-eight hours by Baibars' force of Khwarezmian tribesmen. This battle is considered by many historians to have been the death knell to the Kingdom of Outremer. Although this provoked no widespread outrage in Europe as the fall of Jerusalem in 1187 had done, Louis IX of France organized a crusade against Egypt from 1248 to 1254, leaving from the newly constructed port of Aigues-Mortes in southern France. It was a failure, and Louis spent much of the crusade living at the court of the crusader kingdom in Acre. In the midst of this crusade was the first Shepherds' Crusade in 1251.
Wikipedia: Seventh Crusade