First Ilkhan
The actual founder of the Ilkhanate dynasty was Hulagu Khan, grandson of Genghis Khan and brother of both Möngke Khan and Kublai Khan. Möngke dispatched him to establish a firm Toluid control over the Middle East, and ordered him return to Mongolia when his task was accomplished. Taking over from Baiju in 1255 or 1256, he had been charged with subduing the Muslim kingdoms to the west "as far as the borders of Egypt." This occupation led the Turkmens to move west into Anatolia to escape from the Mongolian tribes. He established his dynasty over the southwestern part of the Mongol Empire that stretched from Transoxiana to Syria. He destroyed the Ismaili Nizari Hashshashins and the Abbasid Caliphate in 1256 and 1258 respectively. After that he advanced as far as Gaza, briefly conquering Ayyubid Syria.
Möngke's death forced Hulagu to return from the Persian heartland for the preparation of Khuriltai (selection of a new leader). He left a small force behind to continue the Mongol advance, but it was halted in Palestine in 1260 by a major defeat at the battle of Ain Jalut at the hands of the Mamluks of Egypt. Due to geo-political and religious issues and deaths of three Jochid princes in Hulagu's service, Berke declared open war on Hulagu in 1262 and possibly called his troops back in Iran. According to Mamluk historians, Hulagu might have massacred Berke's troops and refused to share his war booty with Berke.
Hulagu's descendants ruled Persia for the next eighty years, tolerating multiple religions including Shamanism, Buddhism, and Christianity, ultimately adopting Islam as a state religion in 1295. However, despite this conversion, the Ilkhans remained opposed to the Mamluks (who had defeated both Mongol invaders and Crusaders). The Ilkhans launched several invasions of Syria, but were never able to gain and keep significant ground against the Mamluks, eventually being forced to give up their plans to conquer Syria, along with their stranglehold over their vassals the Sultanate of Rum and the Armenian kingdom in Cilicia. This was in large part due to civil war in the Mongol Empire, and the hostility of the khanates to the north and east. The Chagatai Khanate in Moghulistan and the Golden Horde threatened the Ilkhanate in the Caucasus and Transoxiana, preventing expansion westward. Even under Hulagu's reign, the Ilkhanate was engaged in open warfare in the Caucasus with the Mongols in the Russian steppes. On the other hand, the China-based Yuan Dynasty was an ally of the Ikhanate and also held nominal suzerainty over the latter for many decades.
Hulagu took with him many Chinese scholars, astronomers, and the famous Persian astronomer Nasir al-Din al-Tusi learned about the mode of the Chinese calculating tables. The observatory was built on a hill of Maragheh.
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