In 1260 Mongol forces combined with those of their Christian vassals in the region, including the army of the Armenian Kingdom of Cilicia under Hethum I, King of Armenia and the Franks of Bohemond VI of Antioch.
 This force conquered Muslim Syria, a domain of the Ayyubid dynasty.
They captured Aleppo by siege and, under the Christian general Kitbuqa, seized Damascus on March 1, 1260.
A Christian Mass was celebrated in the Umayyad Mosque and numerous mosques were profaned.
Many historical accounts describe the three Christian rulers Hethum, Bohemond, and Kitbuqa entering the city of Damascus together in triumph, though some modern historians such as David Morgan have questioned this story as apocryphal.

The invasion effectively destroyed the Ayyubids, which was until then a powerful dynasty that had ruled large parts of the Levant, Egypt, and the Arabian Peninsula.
The last Ayyubid king, An-Nasir Yusuf, had been killed by Hulagu this same year.
With Baghdad ravaged and Damascus weakened, the center of Islamic power shifted to the Mamluk sultan's capital of Cairo.

Hulagu intended to send forces southward through Palestine toward Cairo.
So he had a threatening letter delivered by an envoy to the Mamluk Sultan Qutuz in Cairo demanding that Qutuz open his city or it would be destroyed like Baghdad.
Then, because food and fodder in Syria had become insufficient to supply his full force, and because it was a regular Mongol practice to move troops to the cooler highlands for the summer, Hulagu withdrew his main force to Iran near Azerbaijan, leaving behind two tumens (20,000 men) under Kitbuqa, which Hulagu considered sufficient.
Hulagu then personally departed for Mongolia to play his role in the imperial succession conflict occasioned by the death some eight months earlier of Great Khan Möngke.
But upon receiving news of how few Mongols now remained in the region, Qutuz quickly assembled his well-trained and equipped 12,000-strong army at Cairo and invaded Palestine.
He then allied himself with a fellow Mamluk leader, Baibars in Syria, who not only needed to protect his own future from the Mongols but was eager to avenge for Islam the Mongol capture of Damascus, looting of Baghdad, and conquest of Syria.

The Mongols, for their part, attempted to form a Frankish-Mongol alliance with (or at least, demand the submission of) the remnant of the Crusader Kingdom of Jerusalem, now centered on Acre, but Pope Alexander IV had forbidden such an alliance.
Tensions between Franks and Mongols also increased when Julian of Sidon caused an incident resulting in the death of one of Kitbuqa's grandsons.
Angered, Kitbuqa had sacked Sidon.
The Barons of Acre, contacted by the Mongols, had also been approached by the Mamluks, seeking military assistance against the Mongols.
Although the Mamluks were traditional enemies of the Franks, the Barons of Acre recognized the Mongols as the more immediate menace.
Instead of taking sides, the Crusaders opted for a position of cautious neutrality between the two forces.
In an unusual move, however, they allowed the Egyptian Mamluks to march northward without hindrance through Crusader territory and even let them camp near Acre to resupply.
In 1260 Mongol forces combined with those of their Christian vassals in the region, including the army of the Armenian Kingdom of Cilicia under Hethum I, King of Armenia and the Franks of Bohemond VI of Antioch.  This force conquered Muslim Syria, a domain of the Ayyubid dynasty. They captured Aleppo by siege and, under the Christian general Kitbuqa, seized Damascus on March 1, 1260. A Christian Mass was celebrated in the Umayyad Mosque and numerous mosques were profaned. Many historical accounts describe the three Christian rulers Hethum, Bohemond, and Kitbuqa entering the city of Damascus together in triumph, though some modern historians such as David Morgan have questioned this story as apocryphal.
The invasion effectively destroyed the Ayyubids, which was until then a powerful dynasty that had ruled large parts of the Levant, Egypt, and the Arabian Peninsula. The last Ayyubid king, An-Nasir Yusuf, had been killed by Hulagu this same year. With Baghdad ravaged and Damascus weakened, the center of Islamic power shifted to the Mamluk sultan's capital of Cairo.
Hulagu intended to send forces southward through Palestine toward Cairo. So he had a threatening letter delivered by an envoy to the Mamluk Sultan Qutuz in Cairo demanding that Qutuz open his city or it would be destroyed like Baghdad. Then, because food and fodder in Syria had become insufficient to supply his full force, and because it was a regular Mongol practice to move troops to the cooler highlands for the summer, Hulagu withdrew his main force to Iran near Azerbaijan, leaving behind two tumens (20,000 men) under Kitbuqa, which Hulagu considered sufficient. Hulagu then personally departed for Mongolia to play his role in the imperial succession conflict occasioned by the death some eight months earlier of Great Khan Möngke. But upon receiving news of how few Mongols now remained in the region, Qutuz quickly assembled his well-trained and equipped 12,000-strong army at Cairo and invaded Palestine. He then allied himself with a fellow Mamluk leader, Baibars in Syria, who not only needed to protect his own future from the Mongols but was eager to avenge for Islam the Mongol capture of Damascus, looting of Baghdad, and conquest of Syria.
The Mongols, for their part, attempted to form a Frankish-Mongol alliance with (or at least, demand the submission of) the remnant of the Crusader Kingdom of Jerusalem, now centered on Acre, but Pope Alexander IV had forbidden such an alliance. Tensions between Franks and Mongols also increased when Julian of Sidon caused an incident resulting in the death of one of Kitbuqa's grandsons. Angered, Kitbuqa had sacked Sidon. The Barons of Acre, contacted by the Mongols, had also been approached by the Mamluks, seeking military assistance against the Mongols. Although the Mamluks were traditional enemies of the Franks, the Barons of Acre recognized the Mongols as the more immediate menace. Instead of taking sides, the Crusaders opted for a position of cautious neutrality between the two forces. In an unusual move, however, they allowed the Egyptian Mamluks to march northward without hindrance through Crusader territory and even let them camp near Acre to resupply.
Hulagu Khan