Guo Kan was a famous general of Han Chinese descent who served the MongolKhans in their conquest of the West and the conquest of China itself. He descended from a lineage of Chinese generals. Both his father and grandfather served the Khan, while his forefather Guo Ziyi was a famous general of the Tang Dynasty of China. Guo Kan became the first governor of Baghdad during Mongol rule and was instrumental in devising the strategy for the Siege of Baghdad. He served as a Mongol commander and was in charge of Chinese artillery units under the Mongol Yuan Empire. He was one of the Han Chinese legions that served the Mongol Empire, and some of the later conquests of the Mongols were done by armies under his command. The biography of this Han commander in the Yuan Shi said that Guo Kan's presence struck so much fear in his foes that they called him the "Divine Man".
He served Subutai in the conquest of Europe a few years following the fall of the Jin Dynasty. He then served in Hulagu's conquest of the Middle East, playing a major role in the capture and Battle of Baghdad, devising the strategy of using the dikes to drown the Caliph's army, and supervising the reduction of Baghdad's walls. He was then appointed the first Yuan Ilkhanate Governor of Baghdad by Hulagu.
China
Guo Kan took part in the final drive in the conquest of the Jin dynasty, including the capture of Kaifeng. He then helped Subutai conquer West Eurasia, Europe, and the Middle East and was appointed governor of 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, 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 conquest of Europe, it was Subutai who truly commanded. Equally, Guo Kan devised the strategy that reduced the powerful walls of Bagdad in mere days, after destroying her small, but brave and disciplined army in mere hours by drowning them. Promotion by merit, not birth, was one of Genghis Khan's most important innovations, and Guo Kan, from an ethnic group of the Mongols' strongest rivals, was one of his prized generals, loyal to five generations of Great Khans. Nasir al-Din Tusi, Rashid and Bar Heabreus provide accounts of Hulagu's first governors in Baghdad.
