Unified Silla
In the 5 th year of the reign of King Shinmun (685), the local administration was reorganized and the country was divided into 9 Jus and 5 Sogyeongs. In Sangju, one of 9 Jus, Juchiso ( 州治所 ) was established.
※ Current Status of 9 Jus
① 尙州 (Sangju) ② 良州 (Yangsan) ③ 康州 (Jinju) ④ 熊州 (Gongju) ⑤ 全州 (Jeonju) ⑥ 武州 (Gwangju Metropolitan) ⑦ 韓州 (Gwangju in Gyeonggido) ⑧ 朔州 (Chuncheon) ⑨ 溟州 (Gangreung)
The 7 th year of Shinmun's reign (687) saw the completion of the Sangju Fortress, a stonework ( 石築 ) built around Mount King, with the circumference of 1,549 cheol and the height of 9 cheok. Its east gate was called Gongrakmun ( 控洛門 ), west gate Upromun ( 相露門 ), south gate Hongchiguru ( 弘治 舊樓 ), and north gate Hyunmumun ( 玄武門 ). Sources state that inside the fortress were 22 public agencies, including Taepyeongru ( 太平樓 ), Saryeongcheong ( 司令廳 ) and Sangsangwan ( 商山館 ), 21 wells ( 井 ), and 2 ponds ( 池 ).
In the 16 th year of the reign of Gyeongdeok (757), Sabeolju was renamed as Sangju and in the 12 th year of the reign of Hyegong (776), was reorganized and governed as 1 Ju, 10 Guns, and 30 Hyuns. Guns and Hyuns under control of Sangju were divided by Imha-myun, Andong, upstream of the Nakdong River, and the western part includes part of Yeongju, part of Cheongsong-gun, Yecheon-gun, Mungyeong, Uiseong-gun, Gunwi-gun, part of Gimcheon, Cheongwon, Boeun, Okcheon, Yeoungdong, and Hwanggan in Chungbuk.
※ Governors of the Jus ( 州 ) were renamed as Chonggwan and later as Dodok ( 都督 ). The areas formerly known as Ju now belong to provinces. For centralized management, governor-generals and directors were appointed in Guns and Hyuns, respectively. Silla's local administrative system has been considered significant in both administrative and military terms.
In the 6 th year of the reign of Queen Jinseong (889), political scandals led to the uprising of powerful clans and farmers. At that time, Sangju saw the riots of Wonjong ( 元宗 ) and Aeno ( 哀奴 ). Such turbulence prompted the collapse of Silla, which later developed into Later Three Kingdoms, each led by Yanggil of Bukwon, Gungye, and Gyunhwon.
Castles/Fortresses ( 城 ) can be divided into different classifications. First, by geography, mountain fortresses ( 山城 ) and plain ones ( 平地城 ); second, by shape, full-moon ( 滿月城 ), half-moon ( 半月城 ) and Jangseong ( 長成 ); third, by material, earth fortresses ( 土城 ), stone fortresses ( 石城 ) and wooden fences ( 木柵 ). While Up-fortresses ( 邑城 ), built on hills, are most commonly used, mountain fortresses were mainly used during battles. Mountain fortresses, with defensive walls, were built inside steep mountains, overlooking downtown, so that they could provide a space to reserve weaponry, food, and resources, or wells to feed residence and water for people. Gyunhwon Fortress was built in a square on the summit of a mountain, using natural rocks and valleys, and currently, only the site and the shapes of wells remain today. The fortress gives a good view of the surroundings, such as Munjangdae of Sokri Mountain, Gwanumbong, Cheonghwa Mountain and Dojang Mountain.
In the 8 th year of Hyogong's reign (904), the founder of Later Goguryeo, Gungye, invaded Sangju and took over about 30 fortresses. In the 2 nd year of Gyeongmyung's reign (918), Ajagae ( 阿慈蓋 ), father of Gyunhwon and member of a powerful clan, who then lived in Byungpung Fortress, reportedly surrendered to the founder of Goryeo, Taejo Wanggeon.
Gyunhwon's real surname was Lee until he changed it to Gyun. (Samguk sagi)
18 years after Wanggun's enthronement (935), Gyunhwon escaped Geumsansa and turned to Wanggun and was bestowed with Yangju (Yangsan) as Sikup.