The Fall of Outremer
The Mongol Advance
The leader of the westward expansion of the Mongol Empire was Hulagu. He crossed the Oxus River with a huge army in 1256. One of his first orders of business was to destroy the Assassins in Persia, for they had murdered one of Jenghiz Khan's sons. The Mongols did this by methodically reducing castle after castle until there were none left (1257). The Assassin sect never reappeared in Persia.
He then proceeded to Baghdad, which tried everything from force to duplicity to try to turn aside the Mongols. To no avail. They took Baghdad in 1258 and destroyed it, slaughtering thousands. Aleppo followed in 1259 and Damascus in 1260. Everywhere they went the Mongols brought terror. Resistance meant utter destruction: many was the town that was simply eliminated, razed to the ground and its citizens killed or sold into slavery. Cooperation meant a permanent loss of political indpendence and a crushing financial burden.
It's difficult to say where it all would have ended. Where it did end was with the death of the great Khan, Mongka Khan son of Jenghiz, in 1259. When word reached Hulagu, he took a portion of the great western army and headed back to Mongolia. He left one of his trusted commanders, Kitbuqa (Kerbogha), to finish up in Syria and Egypt. It was Kitbuqa who captured Damascus.
Battle of Ain Jalud
Cairo was next on the list. Some of the Crusader States wanted to form an alliance with the Mongols, while others weren't so sure. The allure of destroying Egypt was great, but the Mongols were pretty scary allies. In the end, Armenia and Antioch joined, along with the Templars and Hospitallers.
But this was not the old Egypt. The Mameluks were fierce fighters, and they had outstanding commanders. The Mongols were very far from their bases, and any reverse could quickly turn into a rout.
The decisive battle was at Ain Jalud, near the Egyptian border, in 1260. The Mameluks were led by Qutuz. Some in the Mongol camp argued that there was no need to fight here; all they had to do was out-wait them and the Egyptians would be forced to retreat. When they did, civil war would likely ensue and the Mongols could mop up. Others, however, argued that the army should strike now and not give the Egyptians a chance to fall back to a stronger position. Ahead was the Sinai Desert, a risky crossing for anyone.
In the end, the Mongols decided to attack. Qutuz out-fought them in a day-long battle. The Mongol army was so badly damaged, they did not dare to advance. They retreated, and they kept right on retreating all the way back to Iran and Turkestan.
It was a hallmark battle, for Cairo was the only significant power left to Islam in the Near East. The tide emphatically turned after this, even though in sheer numbers it shouldn't have.
Shortly after the battle, one of the Mameluk commanders murdered Qutuz and took over for himself. His name was Baibars. He led the Egyptians on a counter-offensive of remarkable effectiveness. He was determined first to drive out the Mongols, second to be avenged on Armenia and Antioch for aiding the Mongols, and third to drive the Christians into the sea.