The Mongols were nomads from Western China who grew sheeps and horses on plains called the steppe. Even though China built up the Great Wall, Mongols built the Won Dynasty and  invaded with Genghis Khan being their leader. Then, the Mongols turned to Goryeo and claimed tribute from them. However, when Won's ambassador was killed in the Goryeo's land, Won invaded Goryeo. Their invasion continued for many years, and the country was devastated. Still, the government set up its capital on Ganghwa Island and fought. Meanwhile, common people from Goryeo resisted the Mongols from all across the country. However, when the military government fell and the new government was made, Goryeo surrendered and Goryeo Dynasty returned to Gaesong, its original capital. However, military men called Sam-byeol-cho objected to surrendering and returing to the original capital, fought the Mongols for 3 years, from Ganghwa Island, to Jin Island, and finally they were suppressed in Jeju Island. They are the symbol of independence and resistance of the Goryeo Dynasty.

  Meanwhile, in the western world, Huns came down from Northern Europe and Asia and invaded the Europe. The local kings sought protection for him and his people, and offered land for knights in exchange of loyalty and military assistance. In this case, the kings are lords and the knights are vassals.