He served as a diplomat for sultan al-Kamil from 1226 to 1228 in his negotiations with the Holy Roman Emperor Frederick II leading to the end of the Sixth Crusade.
[4] In 1226, Fakhr al-Din was sent by sultan al-Kamil on a diplomatic mission to Sicily to the court of Frederick II, attempting to forestall the imminent Sixth Crusade, again hoping to regain Christian control of the Holy Land.
[5] When Frederick reached the Holy Land with his small army in the fall of 1228, Fakhr al-Din was once again sent by the sultan in order to dissuade him from continuing his expedition.
[7] Fakhr al-Din was present at the siege of Damascus between June and December 1229, acting as al-Kamil's envoy to the besieged an-Nasir Da'ud.
At al-Salih Ayyub's invitation, the Khwarezmians advanced through Syria and Palestine and on 15 June 1244 successfully conducted the Siege of Jerusalem, leaving the city in ruins.
In 1246, deciding that his Khwarezmian allies were dangerously uncontrollable, he turned on them and defeated them near Homs, killing their leader and dispersing the remnants throughout Syria and Palestine.
[11] Al-Salih's capture of Jerusalem after the Khwarezmian sacking led to the call for the Seventh Crusade, and Louis IX of France took the cross.
Turanshah did not arrive in Egypt until 27 February, and the sultanate was effectively ruled by al-Salih's widow Shajar al-Durr and Fakhr al-Din.
Their vanguard under Robert I of Artois reached the opposite bank first and immediately attacked the camp of the Egyptian army, which was located in front of the city walls.
There a commander and future sultan, Baibars, set a trap for him by locking the gates behind the Crusaders' backs and killing most of them in street fighting.