The Siege of Baghdad, which lasted from January 29 until February 10, 1258, entailed the investment, capture, and sack of Baghdad, the capital of the Abbasid Caliphate, by Ilkhanate Mongol forces and allied troops. The Mongols were under the command of Hulagu Khan, brother of the khagan Möngke Khan, who had intended to further extend his rule into Mesopotamia but not to directly overthrow the Caliphate. Möngke, however, had instructed Hulagu to attack Baghdad if the Caliph Al-Musta'sim refused Mongol demands for his continued submission to the khagan and the payment of tribute in the form of military support for Mongol forces in Iran.