The Battle of La Forbie, also known as the Battle of Harbiyah, was fought October 17–October 18, 1244 between the allied armies (drawn from the Kingdom of Jerusalem and the crusading orders, the territory of Homs, and the Ayyubid-ruled Trans-Jordan) and the Egyptian army of Sultan as-Salih Ayyub, reinforced with Khwarezmian mercenaries.
The capture of Jerusalem by the Khwarezmians in August had excited great alarm among both the Christian and the Muslim states. Al-Mansur, the Emir of Homs and an-Nasr Dawud, ruling in the Transjordan, joined the Templars, the Hospitallers, the Teutonic Knights, and the remaining forces of the Kingdom of Jerusalem to take the field against the Egyptian Sultanate.
The two armies met near La Forbie, a small village northeast of Gaza. On the allied side, al-Mansur was present in person, commanding about 2,000 cavalry and a detachment of troops from Damascus. The overall Christian command was given to Walter IV of Brienne, Count of Jaffa and Ascalon, although the Constable of Jerusalem, Philip of Montfort, was also present. The Christian army consisted of about 1,000 cavalry and 6,000 foot. The Transjordanian forces were under the command of Sunqur al-Zahiri and al-Waziri, and consisted of about 2,000 mounted Bedouin. The Egyptian army was commanded by the young officer Baibars, soon to overthrow his masters and become Sultan of Egypt, and was slightly inferior in strength to its opponents.
Al-Mansur advised the allies to fortify their camp and take the defensive, waiting for the undisciplined Khwarezmians to disperse and leave the Egyptians at a considerable disadvantage. However, Walter, to whom the overall command had been given, was unwilling to refuse battle when he had the advantage of numbers, a rarity for the Christians of Outremer. The allied dispositions were as follows: Christians on the right wing, near the coast, the Emir of Homs and the Damascenes in the center, the Bedouin on the left.
Battle was joined on the morning October 17, with the Christian knights repeatedly charging the Egyptians and fighting up and down the line. The Egyptian army held its ground. On the morning of October 18, Baibars renewed the fight and threw the Khwarezmians against the Damascene troops in the center of the allied line. The center was shattered by their furious attack, and they turned on the allied left and cut the Bedouin to pieces. The Emir's cavalry held fiercely, but they were nearly annihilated, and al-Mansur finally rode from the field with 280 survivors, all that remained of his troops. Threatened by the Egyptians in front and the Khwarezmians on their flank, the Christians furiously charged, to no avail. Over 5,000 of them were killed, and 800 prisoners taken, including Walter of Brienne, William of Chastelneuf, Master of the Hospital, and the Constable of Tripoli.. Of the troops of the knightly orders, only 33 Templars, 27 Hospitallers, and 3 Teutonic Knights survived; Philip of Montfort and the Patriarch of Jerusalem also escaped to Ascalon. However, Armand de Périgord, the Master of the Temple, the Marshal of the Temple, the archbishop of Tyre, the bishop of Lydda and Ramla (St. George), and John and William, sons of Bohemond, Lord of Botron, were all killed.
The Kingdom of Jerusalem suffered worst in the aftermath of La Forbie. It had not been able to put so large an army into the field since the Battle of Hattin, and would never be able to undertake offensive operations again. It brought no lasting success to the Ayyubids; the Khwarezmians were defeated outside of Homs by al-Mansur in 1246 after falling out with the Egyptians, and with the rise of the Mamluk sultans, Baibars came to rule Egypt in 1260. That able and ruthless commander then turned against the Crusader States he had bled white at La Forbie, and devastated them, reducing the Kingdom of Jerusalem to a tiny coastal strip. While Hattin holds great symbolic importance as having led to the fall of Jerusalem, it was La Forbie that truly marked the collapse of Christian power in Outremer.