Branch Secretariat for the Eastern Campaigns

The Yuan set up the Jeongdong Haengseong in Goryeo to prepare the invasion of Japan; it outlived the campaigns as an instrument of interference in Goryeo’s affairs.

After the first invasion of Japan (1274), the Yuan set up the Branch Secretariat in 1280 to prepare the second (1281). Abolished and re-established more than once after the campaigns failed, it survived as a channel between Goryeo and the Yuan and an instrument of interference. The Goryeo king served as its chancellor.

Its Imunso bureau, nominally a court for crimes, arrested anti-Yuan figures and policed Goryeo politics. Pro-Yuan factions repeatedly tried to have Goryeo abolished and turned into a Yuan province, without success. King Gongmin abolished the Imunso in 1356 as part of his anti-Yuan reforms.