Baghdad by Hulagu. At some point after Khubilai Khan's accession as Khan, Guo Kan assisted Khubilai Khan in the conquest of the Southern Song and ultimately the unification of China under the Yuan Dynasty. By this point the Mongol Yuan empire was nearly fully complete, stretching from China across Central Asia, Siberia, and the Middle East to Europe. After Guo Kan returned to China with Hulagu Khan following Möngke Khan's death, Guo Kan helped Kublai Khan in the difficult conquest of Southern Song Dynasty of Southern China. Khubilai's accession as becoming Khan allowed him to select the best Yuan Generals to serve him. Subutai and Jebe both died of old age, and Guo Kan was the last of the 'Gods of War', so the new Great Khan Khubilai assigned Guo Kan to command the final Yuan expedition and reunification of China. Guo Kan reportedly urged Khubilai to adopt a Han Chinese-style dynastic title, establish a capital and central government, and build schools. He reportedly was the general who proposed capturing Xiangyang as a strategy for invading the Southern Song. In 1262, he defeated Song forces in a battle at Xuzhou, and in 1266 urged Khubilai to establish military farms in Huaibei to provide supplies for an invasion of the Southern Song. In 1268 and 1270 he suppressed local rebellions, and then he was sent to participate in the siege of Xiangyang. In 1276, the Song dynasty fell (except for the loyalist movement that lasted until 1279), and Guo served as a prefect for one more year before dying. Guo Kan was a general who helped unify the massive Yuan Mongol empire. He played an important role in their conquests of all corners of the empire, from the east to west. As an example of Mongol meritocracy More than any army in history until the 20th Century, and more so than many even in the modern era, the Mongols promoted strictly on the basis of military skill and ability. Like his brother "dogs of war", Jebe, son of an ordinary warrior in a tribe which had opposed Genghis Khan in his unification of the nomads, and Subutai, son of a blacksmith, Guo Kan, ethnically Han, represented the revolutionary concept of promoting the sons of the most humble or non-Mongol born to command any of the Mongol nobility, including relatives of the Great Khan. Though Batu was nominally in charge of the