Goryeo has been a semi-autonomous vassal state under the overlordship of the Mongol Yuan dynasty since the Mongol invasions of Korea in the thirteenth century.

Starting with King Chungnyeol, prospective rulers of Korea have married Mongolian princesses and are customarily sent to the Yuan Court, in effect, as hostages.

As per this custom, King Gongmin, Goryweo’s current monarch, had spent many years in the Yuan court, being sent there in 1341, before ascending the Korean throne in 1351.

He has married a Mongolian princess who becomes Queen Noguk.

The Yuan dynasty begins to crumble during the mid-fourteenth century.

With the disintegration of Yuan, which has influenced the Korean peninsula since the Mongol invasion of Korea of 1238, Gongmin begins efforts to reform Goryeo government.

His first act is to remove all pro-Mongol aristocrats and military officers from their positions.

These deposed people form a dissident faction that plots an unsuccessful coup against the king.

High official Jo Il-shin even tries to take over the government, but this rebellion is put down by general Choi Young.

During the Mongol invasions of Korea, between the 1250s and the 1270s, the Mongols had annexed the northern provinces of Korea and incorporated them into their empire as Ssangseong and Dongnyeong Prefectures.

In 1356, the Goryeo army retakes these provinces partly thanks to the defection of Yi Ja-chun, a minor Korean official in service of Mongolians in Ssangseong, and his son, Yi Seong-gye.

In addition, Generals Yi Seong-gye and Ji Yongsu lead a campaign into Liaoyang.

The question of land holdings is another important issue.

The land-grant system had broken down, and Mongol-favored officials, along with a handful of landed gentry, own the vast majority of agricultural land, which is worked by tenant farmers and bondsmen.

However, King Gongmin's attempt at land reform is met with opposition and subterfuge from those officials who are supposed to implement his reforms, as they are landowners themselves.

The Wokou, yet another problem encountered during Gongmin's reign, have been troubling the peninsula for some time and have become well-organized military marauders raiding deep into the country, rather than the "hit-and-run" banditry they had originally practiced.

Gongmin calls upon Generals Choi Young and Yi Seong-gye to combat them.