Examined in this article, is the fact that Goryeo imported and employed the Chinese Dang and Sung Institutions, in its initial design of the central government and its operations. Also examined is the interesting fact that it made some changes to that template, in order to address certain unique situations inside Goryeo.
As we all know, the early governmental structure was established in its typical form during the reign of King Munjong. The primary model for that structure was the governmental structure of the late Dang dynasty, but elements from the "5-Dynasties" period and moreover the Sung period were added to it as well. In other words, the new structure of the Goryeo government was an interesting combination of past Chinese institutions, reconstructed to fit and accommodate the Goryeo situation.
At the time, the Dang institution had already been rendered obsolete for a long time, and the Sung institution had a reputation for being too complex and confusing. Nonetheless, the Goryeo people chose to use them as the foundation for their own governmental structure, and even poured in some old Goryeo-type elements into the mix as well. And in the operation of such government, they found their own way to run it, such as the Gyeomjik-je(兼職制) institution, which had the officials assume more than one governmental posts at the same time. One official would have a "main post," and also "assume" another simultaneously. All the high-ranking Jae/Chu(宰樞) posts, with the exception of Mun"ha Shi"jung(門下侍中) and Pyeong"jang-sa(平章事), were the "assumed" ones. In dynastic crises, the Goryeo government had officials who originally had their own main posts assume other posts as well, to oversee and overcome the situation. Later, the central government was redesigned, with Jae/Chu posts at the center.
The description in 『Goryeo Do"gyeong(高麗圖經)』 of the structures and positions of the buildings which housed the Goryeo governmental offices, is one of the scarce sources of information which shows us how the government worked. In Dang and Sung periods, powerful governmental offices such as Jung"seo-seong(中書省) and Mun"ha-seong(門下省) were positioned inside the palace, and also at the left and right side of the Main Hall("Jeong"jeon/正殿," where the Emperor lived and worked), and Sang"seo-seong(尙書省) was placed outside the palace. This separation between the three offices symbolized the separation of powers into three realms.
But in case of Goryeo, the three offices, Jung"seo-seong, Mun"ha-seong, and Sang"seo-seong, were positioned back-to-back in mostly the same place. The Jae/Chu figures, as the center of governmental operations, worked in relatively the same place and oversaw the government there. Although their working area was separated from the King"s area, we can see that the entire process of governmental operations were overseen from a virtually one same place, which must have been an efficient situation for the country runners.