Northeast Asian History Network

The golden age of Koguryo continued throughout early 6th century in the King Munja myeong (reign: 492-519^{[note 001]} period. However, there were signs of political unrest during the King Anjang (reign: 519-531) period. ^{[note 002]}According to the "Chronicles of Japan," King Anjang of Koguryo was murdered. Records indicate that King Anwon (reign: 531-545^{[note 003]} was also murdered.
The above records from the "Chronicles of Japan" are from the period around the death of King Anwon of Koguryo, or King Bak as he was referred to in Japan. The records indicate that large-scale conflict took place over the issue of succession to the throne. The major aristocratic forces had divided into two groups in opposition. The effects of this split in Koguryo aristocracy lasted for a relatively long period. Therefore, Koguryo became vulnerable to external forces.
In 551 CE, the 7th year of King Yangwon of Koguryo (reign: 545-559^{[note 004]}, Baekje and Silla allied forces attacked the Han River basin, and Koguryo was unable to thwart the invasion. Koguryo lost control of the Han River basin which it had controlled for close to one hundred years after the 5th century. With this chaos, the Northern Qi applied diplomatic pressure from the west, and the Göktürks, the emerging powers from Inner Asia, began their military offensive. It was a crisis of domestic trouble and foreign invasion.
At this time, Koguryo signed a secret treaty with Silla and gave up the Han River basin and eastern coast. Instead, Koguryo pursued stability by neutralizing the military threat from the south and attempted to counter the Göktürks' offensive in the west. The Koguryo aristocracy ceased their infighting, and political stability was achieved through compromise. As a result, the “coalition of aristocracy” political system was established.
As stated in the Chinese historical records the "Old Book of Tang," the highest official position in Koguryo was Daedaero. The position was filled every three years, and a qualified person was able to serve consecutive terms. According to the "Records of Goryeo^{[note 005]}" cited in "Hanwon," the aristocratic officials, holding the top five official ranks, decided the most important issues in state politics. Policies were operated through the agreement of the aristocratic powers. Based on this evidence, the Daedaero was estimated to have been elected and reappointed by consensus of the aristocracy. However, as stated in the above "Old Book of Tang," disagreements in the reappointment of the Daedaero were resolved through physical conflict. Notably, the record states that even the king had no control over such affairs. This indicates that the king had no authority to overpower the aristocracy, and disagreements within the ruling aristocrats could result in infighting.
After the mid-6th century, Koguryo politics mainly revolved around the aristocrats and not the king. Nevertheless, political stability was restored to some extent during the King Pyeongwon period (reign: 559-590^{[note 006]}, and a centralized state system continued to be maintained.
The above record from the "New Book of Tang" describes the local government system in Koguryo during the 6th and 7th centuries. This record states that local administrative units were referred to as prefectures, and such administrative units were satellites to a central city. In addition, local government officials were dispatched to each administrative unit. Such local government officials ruled their respective regions as subordinate administrative organizations, and this system was more organized than the previous eras. Although the central throne was weakened, the power of the central state that reached the local communities had in fact been reinforced.