Final answer:
The Song dynasty was conquered by the Mongols, led by Kublai Khan, leading to the establishment of the Yuan dynasty.
Step-by-step explanation:
The Song dynasty was overthrown by the Mongols, a nomadic people from the Gobi. Under the leadership of Kublai Khan, the grandson of Chinggis Khan, the Mongols were able to defeat the Song forces, proclaiming the shift of the Mandate of Heaven to Kublai and establishing the Yuan dynasty. Despite the efforts of the Song dynasty to stabilize and recover after significant military setbacks, they could not withstand the might of the Mongol invasion and eventually succumbed to their power.