Both his father and grandfather served under Genghis Khan, while his forefather Guo Ziyi was a famous general of the Chinese Tang dynasty.
The biography of this Han commander in the History of Yuan said that Guo Kan's presence struck so much fear in his foes that they called him the "Divine Man".
Guo Kan was raised in the household of Prime Minister Shi Tianzhe (who was also a Han, and whose father and two brothers all served the Yuan dynasty).
He then helped Subutai conquer West Eurasia, Europe, and the Middle East and was appointed governor of Baghdad by Hulagu.
[2] By this point the Mongol Yuan empire was nearly fully complete, stretching from China across Central Asia, Siberia, and the Middle East to Europe.
[6][page needed] Guo Kan reportedly urged Khubilai to adopt a Han Chinese-style dynastic title, establish a capital and central government, and build schools.