history
1259 Mongol siege of the Southern Song fortress at modern Hechuan, Chongqing. Great Khan Möngke died during the campaign (most accounts say from a wound or illness), forcing the Mongol armies to retreat from Sichuan — and ending Hulagu's expedition into the Middle East, since Khubilai and other princes turned home to contest the succession. The fortress held out for 36 years, the longest Mongol siege on record.
