Sultan Barbars could now turn his attention to the European Latins and indeed after 1250, the Mamluk Sultanate in Egypt had begun attacking Christian kingdoms. By 1268, Caesarea, Haifa, Arsuf, Galilee and Antioch had been conquered. Pope Gregory IX called in vain for yet another major crusade. However by this time, the 'crusade' itself had become debased currency. Personal ambition and corruption within the Vatican and Europe's nobility had worn down enthusiasm and respect for such endeavors, particularly when at the end of the day those on crusade were fighting the Pope's wars with little linkage to their home principality and rulers. The weak Ninth Crusade accomplished very little. In 1276 Lattakioh was taken by the Mamluk and the King of Jerusalem, Henry II, withdrew to Cyprus and sent an envoy to warn European monarchs about the deteriorating situation in the Levant. Frantic efforts once again to conclude an alliance between Latins in the East and the Mongols failed. Tripoli fell to the Muslims in 1289.

In one of the most important battles in Western history, siege and war comes again to Acre in the last decade of the 13th century. The great fortress /seaport city is now the last major Christian stronghold in the Holy Land. 12,000 brutish Italian crusaders entered the city in 1290 and went on a rampage, killing any man who had a beard. Justifiably angry, Melot Sapheraph, Sultan of Babylon led a large army to Acre. The Grand Master of the Templars, William of Beaujeu, was on excellent terms with the Sultan and met with him in an attempt to avert war. He obtained terms that if each citizen of Acre paid the Sultan one Venetian penny, the truce and peace treaty would be restored. Returning to Acre, William of Beaujeu preached a sermon in the Church of St. Cross but was accused of betraying the city and was angrily driven out by a mob.

The Mamluk Sultan Qalawun attacked Acre, fighting stopped soon thereafter but the Council of Acre refused to remit Muslim prisoners to the Sultan who then declared the long standing peace with the Christians treaty null and void. Qalawun died following a general mobilization order to his army and his son Khalil took charge of the siege of Acre. The population of Acre was 40,000 with 15,000 troops entrenched including the Knights Templar, 2,000 sent by Henry II more arrived May 1291. Khalil's forces may have numbered 20,000 men but most were volunteers working for the siege. 60 Muslim ballista bombed Acre night and day with stones and fire, the psychological effect was devastating. The Hospitallers gave up the fight and took refuge in a church, only to die when it was set afire. The Templars had built a secret 1,000' long tunnel towards the Mediterranean and they silently escaped during the siege. Many believed that if the Knights Templar had remained in Acre, the siege may have been withstood. 500 noblewomen left the city carrying their valuable possessions and jewels and walked towards the sea asking for rescue and refuge. Nonetheless, Acre fell in six weeks, although some believe the Templars held on more than two weeks afterwards in their tower fortress and did not escape by a secret tunnel. By the end of the year, all remaining Crusader cities including Beirut fell to the Mamluks. Christian Europe never again controlled Palestine, Jerusalem and the Holy Land.