At the beginning of 13th century, Genghis Khan (Tiemuzhen in Chinese) united the feuding Mongolian tribes and created the world's most formidable war machine. Sweeping across Eastern Europe and Asia, he created the largest empire the world has ever seen. Kublai Khan, Genghis' grandson, established the Yuan dynasty after taking over the Jin dynasty in the north of China and the remnants of the Song to the south. Adopting the Chinese bureaucracy, Kublai Khan officially established the Yuan dynasty in 1271. The Mongolians treated the Han Chinese harshly and rebellions broke out when the dynasty saw the first signs of weakening.
The rule of the Yuan dynasty, though harsh, did see significant cultural exchanges due to the large size of their territory. The Yuan rulers were known to readily accept new ideas and foreign experts if they could benefit their empire, regardless of whether those experts wanted to volunteer their services or not. Extensive trade routes were established and it was during the Yuan dynasty when Marco Polo supposedly visited China.