The Hidden Troops Cave

Hidden Troops Cave

The so-called Hidden Troops Cave refers to a tunnel system where the garrison of Hongshan Fort could transition from above ground to underground to conceal their troops, protect themselves, wait for the right moment to strike, or set ambushes in open areas. (It is divided into No. 1 Hidden Troops Cave excavated in 2006 and No. 2 Hidden Troops Cave excavated on September 20, 2012.) This is the only most completely preserved ancient three-dimensional military defense system in the country. Within China’s Great Wall defense system, there is nowhere else where the Great Wall, fortresses, and underground Hidden Troops Caves are so closely interconnected. This is a unique site. The Hidden Troops Cave now presented before you is the earliest site and prototype of tunnel warfare in China. If the tunnel warfare of the Eighth Route Army and guerrilla forces during the War of Resistance could strike terror into the hearts of the enemy, making them flee at the mere rumor, then we can imagine that over 500 years ago, the border guards of the Ming Dynasty also used the same wisdom and bravery to keep the invaders outside the Great Wall. In the past, due to lack of development, there were no conditions for entering the cave for tours. People only knew that the “Hidden Troops Cave” had winding paths like a maze, and with the collapse of the cave ceiling, many areas covered by earth, traps inside, and possibly snakes and scorpions lurking, people rarely dared to venture far inside. What the situation inside the cave was like remained unclear. As such, the “Hidden Troops Cave” became a very mysterious and intimidating place. Today, we can confidently enter to feast our eyes, but we must follow the routes indicated by signs to avoid getting lost and unable to get out.

The Hidden Troops Cave winds and twists through the cliffs, connecting vertically and horizontally, with many forks along the way, turning left and right, seemingly without end—truly like a maze. For those unfamiliar with the cave, it is very difficult to find a way out. In addition to the passageways, the cave has earthen rooms on both sides that could be used for habitation, likely reserved for the commanding officers. There are also grain storage rooms, wells, and kitchen facilities inside the cave. As long as enough food is stored, the soldiers hidden in the cave can survive for a certain period without needing to come out. Since the Hidden Troops Cave is more than 10 meters above the bottom of the gully, it is safe from flooding. Over the years, even during mountain floods, the cave has never been submerged. We truly marvel at the wisdom of the ancients.

Starting in 2006, we carried out protective cleaning and clearing of the Hidden Troops Cave. Currently, the section open for visitors to tour is 965 meters long, with a cleared area of about 3,200 square meters, but this is not the entire cave. According to surveys, the total length of the Hidden Troops Caves on both the northern and southern cliffs of the grand canyon is about 3 kilometers, which still awaits further clearing. For the parts already cleared, we have taken protective reinforcement measures on the cave walls and collapsed ceilings. Based on what has been revealed so far, the structure of the Hidden Troops Cave can be divided into ten parts:

First is the tunnel. This is the main body of the Hidden Troops Cave, used during wartime for troop movement, passage, attacks, or entering the cave, and can serve as rest quarters for soldiers during peacetime.

Second is the meeting hall. It is mainly used for gathering discussions on military strategy, planning operations, and deploying combat tactics.

Third is the observation port. Though we call it an observation port, it actually serves multiple functions. It can be used as a watch post to observe movements outside the cave, as a ventilation and lighting device for the cave, and when necessary, as an exit point for attacks. From the entrance setup, after soldiers enter the cave, this area can be guarded by more than one soldier. Even if the fortress is besieged, it is very difficult for the enemy to break into the cave.

Fourth is the living quarters. At certain intervals along the passageway, there are living rooms, likely intended for the command officers to reside and direct their troops.

Fifth is the storage room. It is mainly used to store food and other provisions. No matter the situation, as long as there is enough food, the troops hiding in the cave can hold out for a certain period.

Sixth is the kitchen. It can be used to prepare cooked food. Ingeniously, the kitchen has a chimney leading outside, so even when cooking, the smoke can escape through the chimney without lingering inside to choke the soldiers.

Seventh is the armory. It is mainly used to store arrows, ammunition, and other items for wartime use.

Eighth is the gun platform. Key positions inside the cave are equipped with gun platforms, which can be used to attack invading enemies when necessary, shifting from passive to active defense.

Ninth is the well. This can be considered the lifeline for the soldiers inside the cave. Without water, survival is difficult, let alone holding out or launching attacks.

Tenth is the trap. About three meters deep, the trap is often fitted with antler stakes. Since the cave only allows single-file passage, any enemy entering can only move in a single line. Coupled with unfamiliarity with the cave terrain, they can easily fall onto the antlers, resulting in death or injury. The defending soldiers can guard the opposite side of the trap, making it very difficult for intruders to pass. Seeing this, we can’t help but marvel at the ingenuity of the ancients. Only here can we find physical evidence of an ancient three-dimensional combat facility combining above-ground and underground defenses—an eye-opening experience indeed.

Eleventh is the border trade market. This is mainly found in No. 2 Hidden Troops Cave. A total of 11 types of cultural relics were unearthed from No. 2 Hidden Troops Cave, including stirrups, scales, oil lamps, measuring buckets, measuring cups, measuring grids, leather bags, etc., among which 182 iron stirrups were excavated; 171 copper and wooden scales from the Ming and Qing dynasties; 10 iron oil lamps; 36 wooden measuring buckets, cups, and grids; and 7 leather bags. As a result, archaeological experts say that compared to No. 1 Hidden Troops Cave, which served as an important underground troop transport and ambush defense facility, No. 2 Hidden Troops Cave leans more toward border trade, likely serving as an ancient underground “mall.”

Additionally, once we enter the Hidden Troops Cave, we’ll notice many small niches on the cave walls. These were used by the ancients to place cave lamps for illumination inside. During the cleaning process, we occasionally found broken pottery in these niches, likely remnants of oil lamps. On the ground, we also picked up many fragments from the Ming Dynasty, probably leftovers from the daily lives of the soldiers stationed in the cave. More importantly, in the armory and hall of the Hidden Troops Cave, we can see firsthand ancient weapons such as swords, spears, halberds, swords, quivers, as well as unearthed military gear like helmets and shields. For many young people, these treasures may be seen for the first time. As for the grain and vegetable samples displayed in the niches, they are remnants of food left by the Ming Dynasty soldiers, dating back nearly 500 years—truly rare artifacts.

The construction of the Hidden Troops Cave is ingenious, but what exactly was its purpose? We know that during the Ming Dynasty, the Tatars and Oirats settled in the Hetao region, and the line of the Great Wall near Lingzhou was the northernmost defensive line of the Ming Dynasty in areas such as Ningxia. The Hongshan Fort area, with its flat terrain, was suitable for large-scale cavalry maneuvers, making it the prime target for Tatar nobles leading their armies southward. We also know that the goal of the Tatar nobles riding south was primarily to loot people and wealth, and they would retreat quickly after success. Thus, when they attacked and when they retreated was entirely up to them. But after the mid-Ming Dynasty, building the Great Wall was merely a form of all-weather passive defense. The Tatar and Oirat nobles repeatedly broke through the wall between Lingzhou and Yanzhou and raided Lingzhou and Ningxia (now Yinchuan), looting and then retreating north. But in several of these wall-breaking raids, they never attacked Hongshan Fort. The three-dimensional defense system of Hongshan Fort, including the Hidden Troops Cave, played a significant role.

First, if Hongshan Fort were besieged, the defending soldiers could enter the Hidden Troops Cave, shifting the military struggle underground, preserving their fighting strength, and making it very difficult for enemy cavalry to capture. The defending soldiers could hold out in the cave, waiting for reinforcements—a situation clearly disadvantageous for the enemy cavalry who sought quick raids and rapid retreats with their loot.

Second, when enemy cavalry attacked, the gap they opened could serve as their own retreat route. But if the defending soldiers of Hongshan Fort entered the Hidden Troops Cave, they could launch surprise attacks when the enemy cavalry retreated. Once the enemy cavalry succeeded in looting, they would carry large numbers of captured people, livestock, and cattle, making them much less mobile than during the attack. It would be very difficult for them to retreat smoothly under attack from the cave-defending soldiers, and possibly, the cave defenders and arriving reinforcements would have already set up battle formations, making retreat even harder. Probably for reasons like these, the Tatar and Oirat nobles never attacked Hongshan Fort in their several southern raids, which may be inseparable from the military role of the Hidden Troops Cave.

In the autumn and winter of 2008, another over 200-meter-long tunnel was discovered in the Hongshan Fort scenic area of Shuidonggou, connected to the Hidden Troops Cave. According to local oral history, there were three entrances to the Hidden Troops Cave in Hongshan Fort, and the newly discovered one might be the second entrance. After preliminary clearing, many iron caltrops and some unrotted wood were unearthed, along with three large trap pits with withered grass and sharpened wooden stakes underneath. The tunnel floor was paved with broken bricks from the Ming Dynasty, about 2.1–2.4 meters wide. There was also a section of parallel double tunnels, each only 0.78 meters wide, just enough for one person to pass. In front of the twin tunnels, there were heavy wooden doors. The layout inside the tunnel is more treacherous than the currently open Hidden Troops Cave. After nearly half a year of clearing and reinforcement, the original scene inside the tunnel was restored, and some interactive features were added for visitors to experience the mysteries of the Hidden Troops Cave.

According to historical records, during the Ming Dynasty, the Tatar and Oirat nobles repeatedly broke through the wall between Lingzhou and Yanzhou and raided Lingzhou, Ningxia (now Yinchuan), and other places, looting and then retreating north. But they never attacked Hongshan Fort. This may be related to the significant military role played by the three-dimensional defense systems like the Hidden Troops Cave.

Time Needed

1–2 hours

Transportation

Accessible on foot within the scenic area

Ticket

Included in the Shuidonggou Scenic Area ticket

Opening Hours

8:00-18:00 (tickets may stop being sold about half an hour earlier in winter)

Location of the attraction

Within the Shuidonggou Scenic Area, Shuidonggou Village, Linhe Town, Lingwu City, Ningxia Hui Autonomous Region