[Lee Sang-hoon's Korean History] Gu Jincheon, Creator of the '1000-Step Crossbow', Said "It Only Shoots 30 Steps" Before the Tang Emperor

Silla Specialized Weapon 'Soe-noe'

Sanghoon Lee, Professor at the Korea Military Academy

In 669, an envoy from the Tang Dynasty dispatched to Silla delivered an imperial edict. The specific contents of the edict are not recorded. However, as the Tang envoy returned, he took with him Silla’s crossbow technician Gu Jincheon (Gu Jincheon). This event is notable as it occurred just before the outbreak of the Silla-Tang War. The Tang emperor had Gu Jincheon make a wooden crossbow (mokno). When the wooden crossbow was completed and fired, the arrow only traveled about 30 steps.

The emperor asked, "I heard that in your country, crossbows can shoot arrows up to 1,000 steps. But now I see it only reaches about 30 steps. What is the reason for this?" Gu Jincheon replied, "It is because the quality of the wood is poor. If wood from Silla is brought here, I can make it properly."

The Tang emperor sent another envoy to Silla to procure timber. Gu Jincheon made another wooden crossbow using Silla wood and fired it, but it only reached 60 steps. When the emperor asked for the reason, Gu Jincheon answered, "I do not know the exact reason either. Perhaps moisture seeped into the wood while crossing the sea."

The Tang emperor suspected that Gu Jincheon was deliberately not making it properly and threatened to impose a severe punishment. However, Gu Jincheon never fully revealed his skills.

The story of Gu Jincheon’s 1,000-step crossbow is widely known. It is unknown what punishment he received afterward, but it would have been difficult for him to keep his life after insulting the emperor.

Gu Jincheon’s crossing to Tang occurred in 668, after the fall of Goguryeo, when relations between Silla and Tang were deteriorating. Nevertheless, Tang’s actions demonstrate how outstanding Silla’s crossbow technology was. So how was Silla able to produce crossbows that could shoot as far as 1,000 steps?

Until the 4th to 5th centuries, battles were mainly fought in the field. Through the 6th century, as conflicts among the Three Kingdoms intensified and fortress construction became active, the importance of siege warfare increased.

By the 7th century, the proportion of siege warfare was more than twice that of field battles. Classifying the types of battles recorded in the Samguk Sagi clearly shows that siege warfare became more active than field battles. Accordingly, weapons and equipment for siege and defense developed. Let’s look at the example of Goguryeo in this regard.

According to Yi Ik’s Seongho Saseol (Volume 5), Goguryeo possessed wooden crossbows with a range of 1,000 steps. It is recorded that Emperor Taizong of Tang was hit in the eye by one of these arrows during his 645 campaign against Goguryeo. Although this is a later record with strong legendary elements, it suggests the advanced large-scale crossbow technology of Goguryeo.

The Taebaek Eumgyeong and Tongdian record the length of the wooden crossbow as 1 jang 2 cheok, which roughly converts to about 3.6 meters, indicating it was a large crossbow.

In 669, Tang envoy dispatched to Silla
Took top crossbow technician upon return
Had him make wooden crossbow (mokno), but it was unsatisfactory
Only shot 30 steps; when asked why,
"Wood quality is poor"
Even with Silla wood, only 60 steps
"Moisture seeped into wood crossing the sea"
Never fully revealed his skill

The 1,000-step crossbow (sangno) with a bed appeared in China during the Song Dynasty. In other words, the crossbow manufacturing technology of the Korean Three Kingdoms likely preceded that of China’s Sui and Tang dynasties. So where did Goguryeo’s crossbow technology come from? The Sui Shu (Book of Sui), Volume 81, Biography of the Eastern Barbarians, contains the following passage:

"The craftsmen of the Taibu (Grand Treasury) are not few in number. If the King of Pyeongwon needs them, he can request them himself. However, several years ago, some people secretly brought wealth and used lowly men for profit to take crossbowmen away to your country. Their intention to repair weapons was not good, so fearing rumors outside, was it not theft?"

This passage is part of a letter with a seal sent by Emperor Wen of Sui in 590 to King Pyeongwon of Goguryeo. Crossbow manufacturing was under the jurisdiction of the Taibu Office in Sui.

The Taibu Office included various technicians who made military equipment. Crossbow technicians were assigned to the Gongnoseo (Bow and Crossbow Office) under the Taibu. Goguryeo had recruited these technicians.

This means Goguryeo brought in Sui crossbow technicians before 590. Since this is recorded in an official document with a seal, it can be inferred that it was a significant issue at the time.

After Goguryeo’s fall in October 668, Silla transported 7,000 Goguryeo prisoners to Gyeongju in November of the same year. Since Goguryeo’s influential figures had already been taken to Tang, these prisoners were likely soldiers or technicians captured during battle. From Silla’s perspective, there was no reason to transport thousands of ordinary civilians to Gyeongju. These prisoners were clearly human resources that could be utilized as labor.

In ancient societies, there was little difference in weapon quality. Peacetime troop management was not systematic. Therefore, securing more troops and establishing an efficient mobilization system were key to maintaining strong military power. If there were trained enemy prisoners, it was natural to use them as new military resources.

The Goguryeo prisoners brought by Silla likely hoped to survive by cooperating with Silla rather than facing an uncertain fate as prisoners. They had to survive by either rejoining the Silla army or providing their skills. Silla acquired military intelligence about the Goguryeo region and received military technology from them.

Through this process, Goguryeo’s advanced crossbow manufacturing technology was transmitted to Silla. It is presumed that Silla absorbed Goguryeo’s crossbow technology and even established workshops to specialize in it.

The representative weapon of Silla, the crossbow

According to Seongho Saseol, crossbows made since Goguryeo era
Wooden crossbow length about 3.6m, large-scale crossbow
China’s 1,000-step sangno appeared in Song Dynasty
Korean technology likely ahead of Sui and Tang

Goguryeo prisoners brought by Silla
Transmitted advanced crossbow technology
Weapon specialization before 'Cheonbono'
Siege warfare importance increased, leading to rapid development

Silla established units called Saseoldang (Four Specialized Banners). These were Nodang (Crossbow Banner), Unjedang (Ladder Banner), Chungdang (Ram Banner), and Seoktudang (Stone-Throwing Banner). Nodang specialized in crossbows, Unjedang specialized in ladders for scaling walls, Chungdang specialized in battering gates, and Seoktudang specialized in throwing stones to break walls and buildings.

There is a view that Saseoldang were either combat units or production units. However, since the word 'seol' (設) meaning 'establishment' is included in the unit names, the view that they were production units carries more weight. Either way, they were specialized units created for siege and defense. Among them, Nodang is mentioned first, indicating that Silla placed great importance on crossbows in siege warfare.

The Silla-Tang War intensified from 670. In the early 670s, Tang forces advanced into the Korean Peninsula with nomadic cavalry such as Malgal and Khitan. During this period, Silla established several military units and reorganized officials in the Ministry of War. In 671, a Nodang officer was appointed, followed by a Nosaji (Crossbow House Chief) in 672.

Nodang and Nosaji were undoubtedly official positions related to crossbows. They were likely established to oversee the production and management of greatly improved crossbows. Silla also fought and won battles against Tang forces in the field using long spears and crossbows.

Originally, Silla specialized in crossbows even before Gu Jincheon’s 'Cheonbono' was made. The Nihon Shoki (Chronicles of Japan), Volume 19, records that Silla destroyed Imna (Gaya) using long spears and strong crossbows. This shows that Silla’s main weapons, long spears and crossbows, were known in Japan. Since Gaya fell in September 562, it can be seen that crossbows were already specialized weapons in Silla by the mid-6th century. The Samguk Sagi records that in February 558, Sindeok made a cannon crossbow (pouno) and installed it on Gukwon Fortress. This suggests that large crossbows for fortress defense were installed around that time.

The Xin Tang Shu (New Book of Tang), Volume 200, records the situation in 8th-century Silla. At that time, Silla established checkpoints in border areas and had thousands of crossbowmen guard them. In September 731, King Seongdeok led officials to watch chano (cart crossbow) shooting at the target gate. In April 741, King Hyoseong ordered Jeongjong and Sain to review crossbow troops. Even after the unification of the Three Kingdoms, Silla specialized in and valued crossbows as a main weapon. This technology seems to have developed rapidly after absorbing Goguryeo’s technicians following Goguryeo’s fall.

Professor of Military History, Department of Military History, Korea Military Academy

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