The ruling line of Goryeo, the House of Wang, was permitted to rule Korea as a vassal of the Yuan, which established the Branch Secretariat for Eastern Campaigns (征東行省; literally "Branch Secretariat for Conquering the East") in Korea as an extension of Mongol supervision and political power.

Members of the Goryeo royal family were taken to Khanbaliq, and typically married to spouses from the Yuan imperial clan, the House of Borjigin.

In response, the Mongols backed the rebellion of another group of Goryeo officials in the northwest and created the Dongnyeong Prefecture.

[4][5] Due to the turmoil caused by the Mongol invasions, a number of Koreans from northern Goryeo entered China either as captives or willingly to seek their fortunes elsewhere, especially in the Yuan capitals of Khanbaliq and Shangdu.

Looser control from the Goryeo government resulted in the departure of farming families for Liaoyang and Shenyang to escape tax and labor services.

During the periods leading up to and during the invasions, Korea was effectively forced to serve as a Mongol military base.

[4] David M. Robinson described Goryeo's status as incorporated within the "Great Yuan ulus" but legally distinct from the rest of the empire.

According to Christopher P. Atwood, the Goryeo prince served as the grand councilor (chengxiang) but the secretariat managers (pingzhang) were appointed by the Yuan court.

"[17][18][19][20] The Branch Secretariat for Eastern Campaigns was created in 1280 to mobilize Goryeo resources for the Mongol invasions of Japan.

However even though it was largely staffed by Goryeo officials, it was directly subordinate to the Yuan throne, which stationed Chinese, Jurchens, and Mongols in many of the Branch Secretariat's key posts.

Chungsuk of Goryeo lobbied Mongols, Koreans, and Chinese with ties to the Yuan court for support in regaining his throne from his son and promised them posts in the Branch Secretariat.

[30] Chungseon also benefited from three rest stop villages established by Kublai in 1279 between Goryeo and Khanbaliq that became his base for expansion into Liaoyang.

[32] After the death of Wonjong in 1274, his successor Chungnyeol of Goryeo received Kublai's daughter Qutlugh-Kelmish as a wife, and his reign began a wholesale Mongolization of the Korean court that continued until the middle of the 14th century.

On paper, the official protocol for Korea was that of a subordinate principality, and Korean rulers made lengthy stays at the Mongol Yuan court, both before and after their coronation.

[34] Beginning with the marriage of Chungnyeol and Khudulugh Khaimish, a daughter of Kublai Khan, a total of nine princesses of the Yuan court married into the Goryeo royal family.

[36][37] The Mongols also extracted other tributes such as gold, silver, cloth, grain, ginseng, and falcons from Goryeo.

[41] Yuan envoys regularly visited Goryeo to procure women in the name of the emperor, who distributed them to leading ministers on many occasions.

[44] A native of Qingyuan named Nasen traveled to Khanbaliq in 1355 and wrote a poem comparing the poor existence of Chinese villagers to the life of luxury a Korean woman experienced in the capital.

Empress Gi and her eunuch Bak Bulhwa attempted a major coup of Northern China and Koryo.

By 1356 Goryeo under King Gongmin regained its lost northern territories such as the Ssangseong Prefecture placed under the Liaoyang province by the Yuan.

This changed with the overthrow of Goryeo in 1392 by Yi Seong-gye, founder of Joseon, who cut off relations with the Mongols.

In their place, Goryeo relied on mobilizing men from the general populace on an ad hoc basis depending on military circumstances, while the Yuan-controlled Ssangseong Prefecture and Yuan forces north of the Yalu River became the true defense of Goryeo's northern border.

However the appointment of officers was effectively controlled by the Mongols throughout the mid-14th century and they reserved the right to call on Goryeo's military forces for their own campaigns.

Following the arrest, a number of Goryeo officers raided the homes of several powerful families, but it is uncertain whether this was opportunistic exploitation of the situation or if it was done on the emperor's orders.

Mongol names, which were bestowed by the Yuan court for contributions rendered to the empire, began appearing in the Chinese and Korean populations.

In Khanbaliq and the Jiangnan region, Korean scholars studied Zhu Xi and prepared for the Yuan imperial examinations, while Chinese administrators assigned to Goryeo disseminated Neo-Confucian ideology as well.

[54] Yuan paper currency entered Goryeo's markets as gifts and payments for goods and services rendered.

As a result, Yuan inflationary pressure also affected Goryeo through the royal family and the government elite with ties to Khanbaliq.

The Goryeo royal family maintained several residences in the Yuan capital where they incurred expenses and took loans from merchants.