Kublai Khan (1215 – 1294) was a grandson of Genghis Khan and brother of the Great Khan, Mongke, whom he succeeded in 1260. He conquered the Song Dynasty of southern China and founded the Yuan Dynasty, thus reuniting China for the first time in centuries. He was the nominal overlord of all other Mongol domains, from the Pacific to the Carpathians, but his writ and attention were focused on the territory he personally ruled in China and its periphery, which was wealthier and more populous than all the remaining Mongol khanates put together.
Kublai heeded the advice that “one can conquer an empire on horseback, but cannot rule it on horseback“. After conquering the Song in a campaign that he largely led in person, he spent the bulk of his remaining years in governance rather than military affairs. He ordered expansions along the periphery of his domain that met with mixed success or ended in disaster such as two attempted invasions of Japan that were wrecked by typhoons, but domestic politics and governance interested him more than war.
His reign and founding of the Yuan Dynasty marked the transition that successful nomadic conquerors eventually underwent, eschewing the roughneck ways of the Steppe as they came to appreciate the benefits of settled life, and getting absorbed into the civilization which they had conquered. Kublai encountered fierce resistance from Mongol traditionalists who preferred the old ways and their felt tents to the courtly life in Chinese palaces, but he prevailed in the end.
Kublai’s conquest of the Song Dynasty reunified China after centuries of fragmentation, and the borders of the Yuan Dynasty, encompassing Manchuria, Tibet, and Mongolia, established the broad outline of Chinese territorial suzerainty that survives to this day.