[Lee Sang-hoon's Korean Analogies] Gyeongju Wolji (Wolji Pond) and Wolseong (Wolseong Fortress)

Large-scale fortress construction triggered by war with Tang Dynasty
Wolji Pond symbolizes the 'East Sea,' not just simple landscaping
Wolseong, location of Silla royal palace, has a natural stream to the south and an artificial moat to the north
Ancient waterway 'Balcheon' currently under excavation draws attention

As the COVID-19 situation improves, Gyeongju, one of South Korea's representative tourist destinations, is becoming bustling again. When thinking of Gyeongju, Bulguksa Temple, Cheomseongdae Observatory, Daereungwon Tomb Complex, and Wolseong Fortress come to mind first. For Gyeongju's night view, 'Donggung (Eastern Palace) and Wolji (Moon Pond)' cannot be overlooked. "In February, a pond was dug inside the palace, a mountain was made, flowers and plants were planted, and rare birds and animals were raised." This is the record of the construction of Wolji (Moon Pond) found in the 14th year of King Munmu's reign (674) in the Samguk Sagi. It was formerly called Anapji (Anap Pond). The year 674, when Wolji was constructed, was during the Silla-Tang War, a period when Silla and Tang fought for dominance over the Korean Peninsula.

In January 674, Tang appointed Yu In-gwe as the Commander of Gyerim Province (?林道總管) and organized an expeditionary force against Silla. Weiweijing (衛尉卿) Lee Pil and Right Army General Lee Geun-haeng were assigned to assist Yu In-gwe. Despite the anticipated large-scale invasion by Tang, Silla appeared to be at ease. Silla's composure during an ongoing war was seen as a sign of confidence and an indication that they understood Tang's situation. However, according to the Zizhi Tongjian, in the first year of Shangyuan (674), Weiweijing Lee Pil died under suspicious circumstances during a banquet in September. Lee Pil, who served as deputy commander of the Gyerim Province expeditionary force, was still in the capital in autumn 674. This suggests that there was no Tang invasion of Silla in 674.

The Silla-Tang War, which intensified in 670, unfolded with Tang forces advancing southward into the Korean Peninsula and Silla forces defending in the early 670s. In August 672, Tang forces captured Hansiseong and Maeupseong near Pyongyang and advanced south to Baeksuseong. In response, Silla and Goguryeo restoration forces attacked Tang forces first and gained the upper hand. However, Silla forces pursued the retreating Tang troops to Seokmun (Seohung, Hwanghae) but were counterattacked and suffered a heavy defeat. The defeat at the Battle of Seokmun led Silla to shift its strategy in the war to defense.

After the Battle of Seokmun, Silla strengthened its defenses by expanding or constructing about ten fortresses across the region. In August 672, Jujangseong (Gwangju, Gyeonggi) was built; in February 673, Seohyeongsanseong (Gyeongju, Gyeongbuk); and in August 673, Saryeolsanseong (Jecheon, Chungbuk). In September 673, Gukwonseong (Chungju, Chungbuk), Bukhyeongsanseong (Gyeongju, Gyeongbuk), Somunseong (Uiseong, Gyeongbuk), Isanseong (Goryeong, Gyeongbuk), Juyangseong (Chuncheon, Gangwon), Jujamseong (Goseong, Gangwon), Manheungsasanseong (Geochang, Gyeongnam), and Goljaenghyeonseong (Yangsan, Gyeongnam) were constructed. This large-scale fortress construction strengthened Silla's key strategic points and the capital's defense network.

Silla's first line of defense was the Imjin River, which formed the boundary with Tang forces. Behind the Imjin River, the construction of Jujangseong, Juyangseong, and Jujamseong naturally formed the second line of defense. Centered around the Sobaek Mountain Range, the construction of Gukwonseong, Saryeolsanseong, and Manheungsasanseong strengthened the third line of defense. In the inland Gyeongsang Province, Somunseong, Isanseong, and Goljaenghyeonseong were built, forming the fourth line of defense. Finally, with the construction of Seohyeongsanseong and Bukhyeongsanseong, the fifth line of defense and the royal capital defense line were completed. Thus, Silla organized a five-stage defense line to sequentially prepare for Tang's southward advance.

Silla carried out large-scale fortress construction from 672 to 673. The construction of Wolji in the capital Gyeongju was completed in February 674, coinciding with the conclusion of Silla's extensive fortress-building efforts. In this context, Wolji should not be viewed merely as a landscaping facility. Wolji itself symbolizes the East Sea (Donghae), and the three islands created within Wolji represent the Three Sacred Mountains (Samshinsan) in the East Sea. In the 35th year of King Mu of Baekje (634), a pond was dug south of the palace, and an island symbolizing Bangjangseonsan, one of the Three Sacred Mountains, was created. In other words, the construction of Wolji reflects dragon worship and Taoist immortal beliefs and can be seen as a patriotic project.

Buseoksa Temple, which began construction in February 676 when the Andong Protectorate moved to Liaodong, was a patriotic temple founded under King Munmu's spirit of national defense. Buseoksa also deeply reflects dragon worship elements in its design. Both Wolji and Buseoksa should be regarded as creations embodying the patriotic aspirations of the Silla people facing Tang invasions. The construction of Wolji in February 674 was a natural outcome given Silla's situation on the brink of a major war.

Wolseong (Moon Fortress), inseparable from the patriotic construction of Wolji, is designated Historic Site No. 16 and was the location of the Silla royal palace. It measures 890 meters east-west, 260 meters north-south, with a circumference of 2,340 meters. Located on an isolated hill, its summit is relatively wide and flat. To the south of Wolseong flows the natural Namcheon River, and to the north, an artificial moat was constructed to strengthen defense.

Wolseong North Moat

The walls of Wolseong began construction around the 4th century. Fourteen gates were built: five on the south, three on the west, three on the east, and three on the north. Among these, the southern, western, and eastern gates were used first, and the three northern gates were newly constructed around the 7th century during King Munmu's reign. Until the 5th-6th centuries, Wolseong's main gate faced south. However, with Silla's unification of the Three Kingdoms in the 7th century, changes in the palace's extent and the capital's development led to the main gate being newly built facing north.

In 683, King Sinmun married the daughter of Ilgilchan Kim Heum-un and grandly welcomed her at the palace's north gate. Also, in 734, King Seongdeok ordered officials to enter and reside through the north gate. From this, it is highly likely that Wolseong's main gate was the north gate. Since the Namcheon River flows south of Wolseong, it was impossible to place the main gate there. Considering the topography of the Gyeongju Basin, the main gate of the entire capital was likely the west gate, and the palace (Wolseong) main gate was the north gate.

A notable relic related to Wolseong's role as the royal palace is the moat north of Wolseong. A moat is a pond dug outside the fortress walls and filled with water to prevent enemy invasion. The northern moat of Wolseong was initially a pit-type moat dug and filled with water until the 7th century, later evolving into a stone-built moat that retained water. The Wolseong moat was first identified during a trial excavation in 1984, followed by several excavation surveys. In March 2022, after about three years of restoration, the Wolseong moat was opened to the public.

Gyeongju Balcheon (a stream flowing from Donggung and Wolji, passing north of Wolseong and Gyerim, to Namcheon) excavation site

Both Wolji and the Wolseong moat were constructed with water as a medium and are inseparably related in terms of location. Regarding Wolji's construction, a key concern is where the water used there flows in from and out to. In this context, the existence of Balcheon (Bal Stream) is noteworthy. Currently, Balcheon is an ancient waterway near Wolseong undergoing active excavation. Balcheon generally originates near Wolji and flows southwest, passing horizontally north of Wolseong, then passing through Gyerim (Guilin) west of Wolseong, turning south to join the Namcheon River. From the perspective of Wolseong's northern moat, another stream flows northward in the same direction as the moat. This was the stream flowing between Wolseong and Cheomseongdae.

According to the Samguk Yusa, on the day King Hyeokgeose ascended the throne, a rooster dragon appeared at Al-yeongjeong in Saryang-ri and gave birth to a girl from its left rib. The girl's appearance and face were very beautiful, but her lips resembled a rooster's beak. She was taken to the 'north stream of Wolseong' to bathe, and the beak fell off, hence the stream was called Balcheon. Balcheon is understood to have functioned to draw various water flows originating from the wetlands and springs around Wolji and Hwangnyongsa Temple.

It is presumed that the Balcheon waterway was also maintained when Wolji was constructed in 674. Jo Seong-yoon, team leader at the Silla Cultural Heritage Research Institute excavating Balcheon, explains, "As the Silla royal palace's domain expanded to Balcheon, the northern moat of Wolseong changed in character to become an inner palace pond." After the Silla-Tang War and Silla's unification of the Three Kingdoms in 676, external threats decreased, weakening Wolseong's defensive function. Also, as the palace itself expanded northward, the northern moat of Wolseong transformed into a landscaping pond within the palace.

Professor Sang-Hoon Lee, Department of Military History, Korea Military Academy

This content was produced with the assistance of AI translation services.