Silla built Jujangseong Fortress during the period when it was engaged in a struggle with the Tang Dynasty of China after unifying the three kingdoms of Korea. Notably, an ancient record states that “Jujangseong Fortress was built on Hansan Mountain with a walled perimeter of about 4,360 steps (about 8 km).”
After helping Silla to defeat Baekje and Goguryeo, the Tang Dynasty broke its original promise and revealed its ambition of dominating the Korean Peninsula. In response to this, Silla did not back down but fought against the Tang army along the Imjingang River and in the West Coast area, and built Jujangseong Fortress on Hansan Mountain to defend the area around the Hangang River basin.
Jujangseong was the largest fortress of Silla at that time.
The area that was called Hansan after Silla took control of the Hangang River basin is the current area of Gwangju and Hanam to the south of the Hangang River.
The fortresses remaining from that period include Namhansanseong in the Hansan area, Iseongsanseong (perimeter: 1,653 m) five kilometers to the north, and Daemosanseong (perimeter: 567 m) nine kilometers to the west.
Other than Namhansanseong, none of the fortresses in the surrounding area have a circumference of 4,360 steps (about 8 km)
Looking at the size of Jujangseong Fortress as it is written in various ancient documents, Samguk sagi (History of the Three Kingdoms) describes the circumference of the fortress as 4,360 steps.
In general, one step is equivalent to six cheok, so if the scale used in Samguk sagi was songcheok (1 cheok = 31 cm), the total circumference of Jujangseong would have been 8,109.6 meters (4,360 steps x 6 cheok X 31 cm).
When comparing it to the horizontal distance (7,545 m) of the main wall of Namhansanseong (excluding the outworks), which was identified from a recent measurement, and considering the difference in elevation of the fortress walls, it becomes evident that Jujangseong Fortress was similar in size to Namhansanseong.

This view is supported by a record in Namhanji (Gwangju Town Record), written when the fortress was built during the reign of King Injo, states: “The king ordered the reconstruction of Namhansanseong based on the old site.”
On the other hand, the Geography Section of the Annals of King Sejong, written in the early Joseon period, describes the size of Jujangseong as 3,993 steps.
According to the Yeongjocheok scale used during the reign of King Sejong, one cheok (or ja) was 31.2 cm, which means that the circumference of the fortress would have been about 7,475 meters, a difference of about 600 meters compared to the measurement recorded in Samguk sagi. The size of Namhansanseong Fortress after its reconstruction in the seventeenth century is given as 6,297 steps.
This was measured using the Jucheok scale, and if the length of a jucheok is taken to be 21.5 cm, the total circumference of the fortress would have been 8,123 meters.
When comparing this measurement to the length of 17,400 cheok measured using the Pobaekcheok scale during the reign of King Seonjo, if the length of one pobaekcheok is 46.73 cm, then the total circumference of the fortress would have been 8,123 meters, which is nearly identical to the measurement converted into jucheok.
Based on these records, it can be understood that the wall of Silla’s Jujangseong Fortress was almost the same size as the main wall of Namhansanseong, which was repaired and rebuilt during the reign of King Injo.