sentences:  The Egyptian ruler Aybak was murdered in 1257 and his young son al-Mansur Ali, only 15 years old, became the new sultan, with Qutuz as vice-sultan.The following year (1258) the Mongols led by Hulagu Khan sacked Baghdad.Baibars al-Bunduqdari argued that an-Nasir Yusuf should mobilize his army and make preparations to fight
  the Mongols who were marching towards Syria.