"The house of Ibn Lokman is intact, the chains still there" - King Louis IX of France surrendered to the victorious Mamluks after the lost Battle of Fariskur in the Nile Delta

6 April 1250, King Louis IX of France surrendered to the victorious Mamluks after the lost Battle of Fariskur in the Nile Delta, effectively ending the Seventh Crusade.
"If they decide to return to take revenge or to commit a wicked deed, tell the: The house of Ibn Lokman is intact, the chains still there as well as the eunuch Sobih" (Jamal ad-Din ibn Matruh)

The Battle of Al Mansurah during the Seventh Crusade, St Louis is shown to the right, mourning 

Rumours of a possible, hence unknown Christian power in the Far East, maybe the minions of fabled Prester John, penetrating the Muslim world on its eastern borders set on helping to save the crumbling Crusader states went around in the West since the 1220s. There was indeed a major invasion in Persia, Genghis Khan’s and, ironically enough, the Mongol invasion and destruction of the Khwarezmian Empire of Greater Iran and Afghanistan brought a large band of their now masterless soldiers into Syria. Calling themselves the Khwarezmiyya and fighting as heavy cavalry, they were hired as mercenaries by as-Salih, Sultan of Egypt. As-Salih was engaged in a civil war against his Ayyubid relatives and their Christian allies in in the Levant and during that campaign, in 1244, the Khwarezmiyya managed to capture Jerusalem, Christian again since 1229. In October of the same year, the Khwarezmian mercenaries played an essential part in as-Salih’s Mamluk General Baibars’ decisive victory over an alliance of armies of the Crusader states and the Syrian Ayyubids at the Battle of La Forbie. It was a stroke from which the Christian principalities in the Levant would never recover again. And it was the shock of losing Jerusalem once more to the Muslims that motivated Louis IX of France to take the cross and embark on a crusade, while his envoys negotiated with the Mongols about converting to Christianity to fight the Muslims together. The Mongol khans, Genghis’ successors, demanded the submission of Christian Europe in return and enforced the argument with invasions of Poland and Hungary in the meanwhile.

Ascelin Of Cremone receiving a letter from Innocent IV, and remitting it to the Mongol general Baiju

While Henry III of England licked the wounds from his lost campaign in France, many Central European princes pointed out that the local Mongol threat was a far more pressing concern than distant Jerusalem, Frederick II, the Holy Roman Emperor who had negotiated Jerusalem back from as-Salih’s predecessor al-Kamil 15 years before, wished the Capetian good luck and excused himself with being far too occupied in Northern Italy. Thus Louis IX, about to become Saint Louis, took the Oriflamme and went with 15,000 French and a few English, French and Frisians alone. Bolstered by contingents of the Knights Templar, Knights Hospitaller and Teutonic Knights, the Seventh Crusade landed not in the Holy Land but in Egypt in June 1249. The plan was to conquer Egypt as the nerve centre of anti-Christian resistance and a major supply base for the invasion of Palestine that was about to follow. The first strategic objective was to gain a beachhead at Damietta and that was the last part of the plan that did not end in a disaster. After the Crusaders just had taken the fortress town, the Nile flooded, as it does since time immemorial, and St Louis army was grounded for the next six months. In November, when news of Sultan as-Salih’s death reached the Crusaders, the army marched 30 miles down the Damietta branch of the Nile towards Cairo, tried to take the royal palace at Al Mansurah and promptly received a sound trashing by the Mamluks under Baibars. The days when Crusader armies, admittedly if well led, won against impossible odds were definitely over. Baibars cut off Louis’ retreat back to Damietta, the crusader king tried to trade the place against Jerusalem and a free passage to the Holy Land with his surviving army, the Mamluks urgently advised him to check the facts and laughed in his face and when Louis, finally, tried to flee north in a mad rush, he was brought to bay at Fariskur, 10 miles south of Damietta. His army was annihilated in a running battle and Louis surrendered and was brought back to Al Mansura to be interred at the House of Ibrahim ben Lokman, guarded by a eunuch called Sobih al-Moazami, until a king’s ransom arrived in May and the Raydafrans, as the Arabs called him, was free to leave for Acre. The Seventh Crusade was over.

The Mameluk coup d’etat, St Louis is watching in prison

One third of France’s entire annual revenue was paid as ransom for Saint Louis and those of his men who were taken captive. The Mamluks had assumed power in Egypt after a bloody coup d’etat and allowed the king to go to Acre, still the de facto capital of the Kingdom of Jerusalem, where he met with his queen, Margaret of Provence, after her flight from Egypt with her son, born a day days after the Battle of Fariskur. Margaret had aptly named the infant Jean Tristan. While Tristan probably means “clanking swords” in the old Welsh, Cornish and Breton sources of the famous tale, it was interpreted as “sadness” in the courtly culture of the High Middle Ages. Louis remained in the Holy Land for four years, strengthened what was left of the defences of the Crusader principalities after the defeat at La Forbie, dabbled in the intricate politics and diplomacy of the Near and Middle East, but was at least rewarded with an elephant and a zebra by Aybak, the Mamluk sultan of Egypt when he refused a new alliance with the Syrian Ayyubids. Talks with the Persian assassins of Alamut came to nought as well as further relations with the Mongols who suffered their first major defeat at the hands of Baibars and the Mamluks during the Battle of Ain Jalut in the Jezreel Valley in Lower Galilee in 1260, six years after St Louis had left the Holy Land. In the aftermath, Baibars captured the remaining Crusader strongholds in Palestine except Acre and when St Louis embarked for the next crusade in 1270, it was directed to Tunis and only malicious gossip has it that the place was chosen because the crusader king believed it to be right next to Cairo.

An imaginary portrait of St Louis by El Greco
King Louis IX is shown in one of the most veristic likenesses 
created by the master of Spanish Mannerism, depicting the 
canonised crusader king with the haggard countenance of a Catholic saint 
(fourth quarter of 16th century)

And more about the Battle of Fariskur on: