At that time, an incident took place, which Hulagu did not expect. Before he arrived in Damascus, Hulagu received the news of the death of Mongke Khan, the Khagan of the state of the Tatars. Of course, it was a very great crisis. He was ruling a wide-ranging state which expanded within a record time, and any trouble in the rule might threaten to break up this vast state. On the other hand, Hulagu was one of the candidates to rule the state of the Tatars, as being the brother of Mongke Khan and the grandson of Genghis Khan, and achieved for the Tatars great victories and astounding conquests. He took pride in the fact that he was the first to overthrow the Islamic caliphate along the history. All this made Hulagu qualified to be the first candidate to rule the entire state of the Tatars, instead of ruling only the Middle East region.

For this reason, once Hulagu received the news of the death of Mongke Khan, he decided to leave his army and return in haste to Karakorum, the Mongolian capital, to take part in choosing the successor of Mongke Khan. He appointed in command Kitbuqa, his greatest Mongolian leader, who was, as we have previously mentioned, one of the Christian Tatars.

On his way, and by the time he arrived in the enclave of Persia, Hulagu received the couriers coming from Karakorum telling him that his brother Kublai Khan was chosen as the new Tatarian Khagan. Although the dream of Hulagu was knocked down, as the choice was opposed to his expectations, as well as to the principles of rule stipulated by Genghis Khan, he accepted it quietly, and preferred to remain in the Middle East, given that he had seen its huge resources. But he did not return to Shaam once again. He went to Tabriz (presently in Iran) and made it the main centre of administering all those vast possessions.

Regardless of its impregnability and moderate atmosphere, it was in the middle of all the large territories under Hulagu's sovereignty. His sovereignty extended from the territories of Khwarezm including Kazakhstan, Turkmenistan, Uzbekistan, Afghanistan and Pakistan, passing through the enclaves of Persia and Azerbaijan, ending with Iraq, Turkey and Shaam. He also did not return to Shaam once again because there remained only small parts, in which there were no big cities, especially after he had received the flight news of An-Naasir Yoosuf and his army southward to Palestine, leaving Damascus unprotected. But Hulagu sent an important message to Kitbuqa, in which he placed a strong emphasis on the necessity of arresting the wretch and rebel, An-Naasir Yoosuf Al-Ayyoobi.

http://300035.dotdothktrade.tech/en/artical/3408721/The-death-of-Mongke-Khan