The Destruction of Baghdad. 10 February 1258.

In 1257, Möngke resolved to establish firm authority over Mesopotamia, Syria, and Iran. The khagan gave his brother, Hulagu, authority over a subordinate khanate and army, the Ilkhanate, and instructions to compel the submission of various Muslim states, including the Abbassid caliphate. Though not seeking the overthrow of Al-Musta’sim, Möngke ordered Hulagu to destroy Baghdad if the Caliph refused his demands of personal submission to Hulagu and the payment of tribute in the form of a military detachment, which would reinforce Hulagu’s army during its campaigns against Iranian Ismaili states.

After defeating the Assassins, Hulagu sent word to Al-Musta’sim, demanding his acquiescence to the terms imposed by Möngke. Al-Musta’sim refused, in large part due to the influence of his advisor and grand vizier, Ibn al-Alkami. Historians have described various motives to al-Alkami’s opposition to submission, including treachery and incompetence, and it appears that he lied to the Caliph about the severity of the invasion, assuring Al-Musta’sim that, if the capital of the caliphate was endangered by a Mongol army, the Islamic world would rush to its aid.

Although he replied to Hulagu’s demands in a manner that the Mongol commander found menacing and offensive enough to break off further negotiation, Al-Musta’sim neglected to summon armies to reinforce the troops at his disposal in Baghdad. Nor did he strengthen the city’s walls. By January 11 the Mongols were close to the city, establishing themselves on both banks of the Tigris River so as to form a pincer around the city. Al-Musta’sim finally decided to do battle with them and sent out a force of 20,000 cavalry to attack the Mongols. The cavalry were decisively defeated by the Mongols, whose sappers breached dikes along the Tigris River and flooded the ground behind the Abbasid forces, trapping them.

The Abbasid caliphate could supposedly call upon 50,000 soldiers for the defense of their capital, including the 20,000 cavalry under al-Musta’sim. However these troops were poorly equipped and poorly disciplined. Although the caliph technically had the authority to summon soldiers from other Muslim empires to defend his realm, he either neglected to do so or lacked the ability to. His taunting opposition had lost him the loyalty of the Mamluks, and the Syrian emirs, who he supported, were busy preparing their own defenses.

On January 29, the Mongol army began its siege of Baghdad, constructing a palisade and a ditch around the city. Employing siege engines and catapults, the Mongols attempted to breach the city’s walls, and, by February 5, had seized a significant portion of the defenses. Realizing that his forces had little chance of retaking the walls, Al-Musta’sim attempted to open negotiations with Hulagu, who rebuffed the Caliph. Around 3,000 of Baghdad’s notables also tried to negotiate with Hulagu but were murdered. Five days later, on February 10, the city surrendered, but the Mongols did not enter the city until the 13th, beginning a week of massacre and destruction.

Many historical accounts detailed the cruelties of the Mongol conquerors.

The Mongols looted and then destroyed mosques, palaces, libraries, and hospitals. Grand buildings that had been the work of generations were burned to the ground.

The caliph Al-Musta’sim was captured and forced to watch as his citizens were murdered and his treasury plundered. According to most accounts, the caliph was killed by trampling. The Mongols rolled the caliph up in a rug, and rode their horses over him, as they believed that the earth would be offended if it were touched by royal blood. But the Venetian traveller Marco Polo claimed that Al-Musta’sim was locked in a tower with nothing to eat but gold and “died like a dog”.

Baghdad was a depopulated, ruined city for several centuries and only gradually recovered some of its former glory.