Chinese siege defence

Per the request of my long time reader Yevon, and also due to my recent interest in Stronghold Warlords, let's talk about Chinese siege defence!

Overview

The art of siegecraft is incredibly sophisticated and complex, often involving meticulous planning on logistics, morale, tactics, intelligence, diplomancy, and so on. However, when it comes to taking direct action against a fortification, the options are surprisingly few. The vast majority of siege tactics all over the pre-modern world generally revolved around contravallation, artillery bombardment, tunnelling and sapping, escalade, siege tower, battering ram as well as thermal attack, and China was no exception. As such, Chinese countermeasures to most siege tactics were more or less identical to methods developed elsewhere.

What set them apart from other cultures was that larger Chinese walls allowed the defenders to set up heavier and more complex machinery on the battlement, or even move their own siege engines anywhere on the wall to counter enemy siege engines, without the need of artillery position prebuilt into the wall.

1) Contravallation countermeasure

Contravallation, known as Ju Yin (距堙 or 距闉) and Chang Wei (長圍, lit. 'Long encirclement') in Chinese, was a tactic used by pretty much all pre-modern armies to lay siege to a fortified position by constructing a line of siegeworks to partially or completely surround the target fortification. Contravallation allowed the attacking party to enforce blockade more effectively, reconnoitre enemy defensive layout from a high position, and even pour suppressive fire against defending troops on the wall. It could also serve as a base for launching assaults against enemy fortification, or for constructing further earthworks such as siege ramps or tunnels. Chinese contravallation tactics range from simple Jin Lang (井闌) towers built atop artificial mounds and ditches, to more elaborate palisades and fortified arrow towers, to full-blown encirclement with networked siege castles.

1.1) Sortie

Due to the limitations of pre-gunpowder siege weapons (stone throwers have limited range and generally cannot demolish fortified structures faster than they can be repaired/rebuilt), it was extremely difficult to stop a contravallation attempt once the construction process began. As such, the best countermeasure to enemy contravallation was to sortie out to destroy enemy fortifications, siege engines and earthworks before their completion, preferably with armed escorts and covering fire from friendly troops on the wall. While undoubtedly effective, this tactic was not without downsides, as it was extremely risky and wasn't always viable against numerically superior enemy.

1.2) Counter-tunnel

Just as tunnelling could be used to bring down a fortification, so too it was an effective countermeasure against contravallation. Countermining tactics will be discussed in section 3.2) Countermining.

1.3) Tower hoarding

Multi-storey hoarding built on the wall to offset the height advantage of enemy contravallation.

Another countermeasure to enemy contravallation was to build tall wooden towers on the wall in direct opposition to enemy towers on the contravallation line. While this method won't be able to circumvent enemy blockade, it can still offset other dangers posed by contravallation such as preventing the enemy from pushing the contravallation line too close to the wall, as well as buying precious time for the defenders as the enemy would be forced to either change tactic or waste more time and resource to construct ever taller towers and siege ramps in an attempt overcome the strengthened defence.

2) Artillery defence

Artillery bombardment was one of the most dangerous threats to fortification, and as such deserve special attention from fort builders and defence planners alike. Aside from careful fortification planning, the primary countermeasures to artillery bombardment were sortie (see above) and counter-battery fire.

2.1) Counter-battery artillery

The most direct response to enemy artillery bombardment was to set up artillery of your own. The purpose of counter-battery fire was to neutralise enemy artillery as well as its supporting elements such as siege crews, engineers, spotters, and commanders. Counter-battery fire may be used proactively and reactively.

A platform with five whirlwind trebuchets, from 'Wu Bei Zhi (《武備志》)'.

In general, siege artillery used in defence of a fortification held the advantages of good protection, better field of vision, and longer range, but also disadvantaged by low manoeuvrability, limited angle of attack, and limited space. Careful consideration on artillery placement was thus crucial to maximise the advantages of defensive artillery while minimising the drawbacks.

Many siege artillery such as trebuchets, rampart crossbows, cannons and rockets were also crucial to siege defence. Unfortunately, due to constraint on the length of this article, individual siege artillery will not be covered in detail here.

2.1.1) Special ammunition

Beyond the usual stones, clay balls (that shatters on impact and prevents the enemy from shooting it back), heavy bolts, and the occasional carcasses, Chinese siege crews were known to use many unorthodox ammunition such as barrels filled with burning charcoal, caltrops, and human excrement. Shown below are some examples of special ammunition used in siege defence.

Yellow clay ball

A simple, easily-manufactured trebuchet ammunition made of yellow clay (chosen for its relatively high stickiness, thus easier to shape into a ball), mainly for anti-personnel use. 

Clay ammunition confers several advantages over typical stone ammunition, namely its lightweight allows the defenders' stone throwers to outrange their attackers' counterparts, and its consistent shape and weight (compared to stone) also allow for more stable trajectory and precision. On top of that, clay ball shatters on impact, thus preventing the enemy from reusing it.

Tie Zui Huo Yao (鐵嘴火鷂, lit. 'Iron-beaked fire sparrowhawk') and Zhu Huo Yao (竹火鷂, lit. 'Bamboo fire sparrowhawk')

Zhu Huo Yao (left) and Tie Zui Huo Yao (right), from 'Zhan Shou Quan Shu (《戰守全書》)'.

Tie Zui Huo Yao and Zhu Huo Yao are two basic gunpowder-based incendiary projectiles used by Chinese siege crews.

Tie Zui Huo Yao is a bundle of gunpowder-laced reed tied to a wooden weigh connected to an iron hoop. The hoop allows it to be hooked to, and launched from, the release pin on the trebuchet's arm (as flaming projectile may damage the sling pouch of the trebuchet, or even the trebuchet itself).

Zhu Huo Yao is a bamboo basket filled with black powder and pebbles to increase its weight. The basket is also sealed with several layers of paper to prevent gunpowder from leaking out. Similar to Tie Zui Huo Yao, it has a bundle of reed tied to one end of the bamboo basket.

Huo Qiu (火毬)

Drawing of a Gun Qiu, from 'Wu Bei Zhi (《武備志》)'.

Huo Qiu is a type of primitive non-metallic bomb launched from a trebuchet.

For more details, please see my other post.

Jin Huo Guan (金火罐, lit. 'Metallic-fire can')

Drawing of a Jin Huo Guan, from 'Zhan Shou Quan Shu (《戰守全書》)'.

Jin Huo Guan is a special trebuchet ammunition that is essentially a burn-proof container made of multiple layers of hemp shives, mud, wheat flour and pig bristle, and wrapped in thick water-soaked felt. It is filled with molten iron immediately before being flung by a trebuchet. It is also known as Jin Zhi Pao (金汁砲, lit. 'Liquid metal bomb').

Jin Huo Guan has limited range and accuracy compared to normal trebuchet projectile due to the fact that molten iron cools off and solidify very quickly, thus forcing the trebuchet crews to launch the container as quickly as possible. It is primarily used as an anti-personnel weapon, where its red-hot splash can make short work of large crowds of enemy troops.

3) Tunnelling and sapping defence

Tunnelling and sapping were two closely related, but different siege tactics. Despite both tactics involved digging and aimed for the same outcome (i.e. to either undermine and collapse the fortification, or bypass it), they were conducted differently.

As its name suggests, tunnelling operation involved digging one or more tunnels under enemy fortification. The digging operation could be conducted far away from defenders' position and, with any luck, undetected by the defenders. The primary purpose of tunnelling defence was to prevent enemy tunnellers from completing the siege tunnel, through detecting and pinpointing tunnelling activities, as well as utilising various countermining tactics to kill the tunnellers and destroy their incomplete tunnel.

On the other hand, sapping involved mining the base of enemy fortification directly, or excavating a short tunnel very close to enemy fortification. As such, sapping operation tend to be highly visible to the defenders, and would often invite immediate response. Besieging sappers also had to contend with withering defensive fire, only relying on trenches, gabions, and mobile shelters such as siege mantlet and siege gallery (also known as "Welsh cat") to protect themselves.

3.1) Detecting tunnelling activities

Before a countermeasure to enemy tunnelling operation could be devised, one must be able to detect such operation in the first place. The first step of detecting enemy tunnelling operation was to erect observation towers to monitor any suspicious activity coming from enemy siege camp. Once it was confirmed that they were indeed digging, the defenders would dig small dry wells at multiple locations behind the wall to pinpoint the location of enemy tunnels, as well as preparing counter-tunnels of their own. Guard dogs were used to patrol these counter-tunnels when no human was present.

Di Ting (地聽, lit. 'Ground listener') or Weng Ting (甕聽, lit. 'Urn listener')

Differently shaped Di Ting, from 'Zhan Shou Quan Shu (《戰守全書》)'.

Di Ting is simply an urn with its bottom removed and covered with a layer of thin cowhide, and serves as a hearing aid that helps the defenders to track down enemy tunnellers. It is usually placed inside a dry well before use.

3.2) Countermining

For the most part, surrounding a fortification with deep moat as well as building a fortification on solid rock were considered the most effective defence against undermining. Nevertheless, these two methods were not foolproof and not always possible to implement, therefore other defences were needed.

3.2.1) Intercepting trench

The simplest countermeasure against enemy tunnelling was to dig a deep trench to cut off the planned route of enemy tunnel. As enemy tunnellers inevitably dug into the trench, they would be killed off by the defending troops laying in ambush. Alternatively, the defenders could dig a counter-tunnel of their own from inside the trench.

3.2.2) Tunnelling over enemy tunnel

Known as Fan Shen Ku (翻身窟, lit. 'Body-flip burrow') in Chinese, this countermining tactic sought to dig a counter-tunnel that goes above enemy tunnel. As soon as two tunnels overlap, the defenders would dig small drain holes into the tunnel below, then pour a special concoction of boiling human faeces, various poisons, stink ingredients and lime onto enemy tunnellers below. The special concoction would cause horrific injury and secondary infection upon skin exposure, and fill the tunnel with unbearable stench afterwards.

Mu Jian (木檻, lit. 'Wooden tub'), Zhu Pan (注盤, lit. 'Injecting tray'), and Pi Tou Cao (皮透槽, lit. 'Leather seeping trough')

Mu Jian (left), Zhu Pan (middle) and Pi Tou Cao (right), from 'Wu Bei Zhi (《武備志》)'.

Mu Jian, Zhu Pan and Pi Tou Cao are tools used to drip the special concoction into the drain hole. Mu Jian is a wooden container used to store and transport the concoction, while Zhu Pan and Pi Tou Chao are funnels made of wood and cowhide respectively.

3.2.3) Tunnelling into enemy tunnel

The second countermining tactic was to dig a counter-tunnel that preemptively connects into enemy tunnel, then either launch a sortie to kill enemy tunnellers inside, or blow smoke and poison gas into the tunnel to suffocate them. While it sounds very simple and straightforward, countermining was actually a remarkably sophisticated process that involved manufacturing, laying and sealing of ceramic smoke pipes, digging branch tunnels at a set interval as safe rooms for the tunnellers once the smoke start pumping (as well as hiding spots to launch ambush), preparing concealed storing space to hide digging equipment, clearing out debris dug out by the tunnellers, preparing special breaching equipment used to storm into enemy tunnel, and making blockades to prevent counter-storming.

Lian Ban (連版, lit. 'Linked planks')

Lian Ban is a massive tunnel-fighting shield/barrier that requires multiple handlers to carry. It is made from assembled wooden planks and comes with multiple loopholes so that soldiers can fight from behind the safety of the shield. Lian Ban doesn't have a standardised shape and size, but is made to match the dimensions of the tunnel.

Feng Shan Che (風扇車, lit. 'Wind fan vehicle')

Drawing of a Feng Shan Che, from 'Wu Bei Zhi (《武備志》)'.

Feng Shan Che is a cranked rotary fan similar to the fan used in Chinese winnowing machine that can be used to blow smoke into the tunnel. It is however less efficient than bellow-and-pipe method.

Pi Li Huo Qiu (霹靂火毬)

Drawing of a Pi Li Huo Qiu, from 'Wu Bei Zhi (《武備志》)'.

Pi Li Huo Qiu is a poison smoke bomb used in conjunction with Feng Shan Che to smoke out or suffocate enemy tunnellers.

Tu Se Zhan Lian (土色氈簾, lit. 'Earth-coloured felt screen')

Drawing of a Tu Se Zhan Lian, from 'Wu Bei Zhi (《武備志》)'.

Tu Se Zhuan Lian is a camouflaged cover that hides the exit of counter-tunnel from enemy detection. It allows the defenders to ambush enemy tunnellers without revealing the position of their own counter-tunnel.

3.2.4) Tunnelling under enemy tunnel

The fourth countermining tactic was to dig a counter-tunnel that goes below enemy tunnel. Then, the defenders could either conduct a controlled removal of timber supports inside their tunnel, or create a camouflet, causing the collapse of both tunnels.

3.2.5) Counteroffensive tunnel

The fifth countermining tactic was to simply dig a counter-tunnel, either directly into enemy siege camp or behind enemy line. This allows the defenders to launch surprise counterattack against the enemy from a direction they least expect.

3.3) Sapping defence

Defending against sapping was little different from defending against direct assault (see below), although sappers by their nature tend to be better protected than troops storming the wall, rendering defensive fire less effective. Besides, special care should be taken to ensure that even dug-in sappers that were otherwise unreachable by defenders on the wall can be dealt with.

You Huo Tie Xiang (游火鐵箱, lit. 'Wandering fire iron box')

Drawing of a You Huo Tie Xiang, from 'Zhan Shou Quan Shu (《戰守全書》)'.

You Huo Tie Xiang is an iron basket connected to an iron chain. It is usually filled with burning firewood, Chinese mugwort (the smoke of burning Chinese mugwort can cause convulsion and epilepsy if inhaled in large amount) and wax, then lowered from the wall into enemy trench or sap to burn the sappers inside. Enemy sappers that try to douse the flame with water will inevitably trigger a wax fire, causing horrific burning.

4) Direct assault countermeasure

Once a siege had progressed to this phase, the countermeasures also became more straightforward, and sometimes more desperate. The primary purpose of direct assault countermeasure was to prevent the enemy from coming over or through the wall, achieved by either physically stopping them, or through killing of enemy troops and destroying their siege engines.

4.1) Anti-escalade 

4.1.1) Passive anti-access

While escalate tactic was often carried out with scaling ladders and siege towers, it is perfectly plausible to climb over a defensive wall barehanded. Therefore, posting sentries and night watchers to prevent enemy infiltrators from sneaking pass the wall was of utmost importance, and this was especially true for large walled settlements like Chinese cities.

However, manpower shortage often became a serious issue during a drawn-out siege. Defenders struggling with manpower shortage often had to assign patrolling duty to a handful of sentries, or force unreasonably long shift onto them. As casualties and fatigue mounted, this would undoubtedly reduce the effectiveness of the patrols. As such, various passive anti-scaling devices were designed to mitigate this issue and lighten the workload of sentries.

Mu Cheng (木城, lit. 'Wooden fort')

Drawing of a Mu Cheng, from 'Wu Bei Zhi (《武備志》)'.

Mu Cheng is a wooden plank fence with two spiked logs mounted at the top between two fence pegs, in a manner not dissimilar to a rolling pin. The rollable spiked logs serve as the pre-modern equivalent of barbed tape. The fence can be set up on its own to protect a military camp, or mounted on top of a wall as additional deterrent to enemy climbers.

Nai He Mu (奈何木, lit. 'Helpless log')

Drawing of a Nai He Mu (top), as well as Nai He Mu with attached stones and brambles (bottom), from 'Zhan Shou Quan Shu (《戰守全書》)'.

Nai He Mu is essentially a wooden log nailed full of spikes that can be hung from a wall, with additional ropes tied with rocks on one end and thorny brambles on the other end hung from the log. A row of Nai He Mu hanging on a wall will create a spiked barrier along the middle part of said wall, which is nearly impossible to bypass. On top of that, if an enemy climber attempts to cut or pull away the thorny brambles (or otherwise fiddle with the device), he will inevitably cause the rock tied to the other end of the rope to drop to the ground, creating a large thump and alerting nearby sentries.

Cervus (plural Cervi) is a primitive version of this device used by ancient Romans. It consists of only wooden branches projecting horizontally from a wall.

Fu Li (浮籬, lit. 'Floating fence')

Drawing of a Fu Li with two stones hanging from it, from 'Zhan Shou Quan Shu (《戰守全書》)'.

Fu Li is an anti-scaling device that serves similar function to Nai He Mu, except that a bamboo fence is mounted at the wall surface in place of the spiked log. Like Nai He Mu, it also comes with hanging rocks that serve as alarm to nearby sentries.

4.1.2) Anti-scaling

Cha Gan (叉竿, lit. 'Fork pole') and Di Gao (抵篙, lit. 'Prop pole')

Di Gao (left) and Cha Gan (right), from 'Zhan Shou Quan Shu (《戰守全書》)'.

Di Gao and Cha Gan are simple pole fork that can be used to push enemy scaling ladders off the wall. While only two forks are shown here, other similar weapons, such as Chan (鏟), can also be used for the same purpose.

Lian Jia Bang (連枷棒)

Drawing of a flail, from 'Wu Bei Zhi (《武備志》)'.

While a potent field weapon in its own right, flais is especially useful for siege defence as it allows its users to attack enemy wall climbers without exposing themselves.

For more details, please see my other post.

Cuo Shou Fu (剉手斧, lit. 'Hand-guillotine axe')

Drawing of a Cuo Shou Fu, from 'Zhan Shou Quan Shu (《戰守全書》)'.

Cuo Shou Fu is a unique weapon that is essentially to a hoe with sharpened axe blade in place of its hoe blade. In other words, a long-shafted war adze. It can be used to chop off the fingers of enemy climbers as soon as they climb to the top of the wall.

4.1.3) Attacking the base of the wall

Fei Gou (飛鈎, lit. 'Flying hook')

Drawing of a Fei Gou, from 'Wu Bei Zhi (《武備志》)'.

Fei Gou is a sharpened grappling hook that can used to pull up unsuspecting enemy troops from the base of a wall, before releasing them and let them fall to their death.

Gun Mu Lei Shi (滾木檑石, lit. 'Rolling log and pestling rock')

A wooden log with barbed spikes (top), a clay log (middle) and a brick log (bottom), from 'Fang Shou Ji Cheng (《防守集成》)'.

Gun Mu Lei Shi, often shortened to just Lei (檑), refers to all kinds of throwables used in siege defence. It can be broadly categorised into two groups, namely Gun Mu (滾木, lit. 'Rolling log') or Lei Mu (檑木, lit. 'Pestling log'), i.e. wooden logs, as well as Gun Shi (滾石, lit. 'Rolling rock') or Lei Shi (檑石, lit. 'Pestling rock'), i.e. rocks.

In its most basic form, any suitably large tree trunk or sufficiently heavy rock can be used in siege defence. Nevertheless, both wood and stone are valuable resources during a siege that could be better utilised elsewhere, so it's important to prepare for alternative sources in the event of a wood or stone shortage. Taking advantage of the relative abundance of clay, Chinese people fashioned Ni Lei (泥檑, lit. 'Clay pestle') out of clay mixed with pig bristle or horsehair, and fired log-shaped bricks known as Zhuan Lei (磚檑, lit. 'Brick pestle') to supplement wooden and stone Lei.

Lei Mu Jia (lit. 'Pestling log rack') and Lei Shi Jia (擂石架, lit. 'Pestling rock rack')

Lei Shi Jia (left) and Lei Mu Jia (right), from 'Fang Shou Ji Cheng (《防守集成》)'.

Lei Mu Jia and Lei Shi Jia are prefabricated wooden racks that can be used to store—and dump wooden logs and rocks onto enemy troops.

Xuan Shi (懸石, lit. 'Hanging stone')

Drawing of a Xuan Shi, from 'Zhan Shou Quan Shu (《戰守全書》)'.

Xuan Shi is simply a heavy rock tied to an iron chain. It is simply a reusable variant of the standard Lei Shi.

Che Jiao Lei (車腳檑, lit. 'Wagon leg pestle')

Drawing of a Che Jiao Lei (highlighted), from 'Wu Bei Zhi (《武備志》)'.

Che Jiao Lei is literally an improvised Lei made out of a wooden wheel and axle taken from a wagon.

Ye Cha Lei (夜叉檑. lit. 'Yaksha's pestle')

Drawing of a Ye Cha Lei, from 'Zhan Shou Quan Shu (《戰守全書》)'.

Ye Cha Lei is a special-made, reusable version of Lei Mu. It consists of a heavy elm log nailed full of iron barbed spikes, two wooden wheels mounted at both ends of the log, as well as iron chains connecting the wheels to a crank. The wheels help to facilitate the retrieving process by preventing the spiked log from getting stuck in the ground or wall surface.

Lang Ya Pai (狼牙拍, lit. 'Wolf's tooth swatter')

Two Lang Ya Pai hanging from cranks, from 'Wu Bei Zhi (《武備志》)'.

Lang Ya Pai is a heavy rectangular board made of elm wood, with hundreds of barbed iron spikes nailed to its underside, as well as four blades on its sides. It is the largest and most formidable of the droppable siege defence weapons.

Tie Huo Chuang (鐵火床, lit. 'Iron fire bed')

Drawing of a Tie Huo Chuang, from 'Zhan Shou Quan Shu (《戰守全書》)'.

Tie Huo Chuang is a large iron grate with four wooden wheels and connected to two iron chains. During a siege, reed and other combustible materials are tied to the grate and set on fire, then the grate is lowered from the wall to literally barbecue enemy troops at the base of the wall.

It can also be used for illumination purpose.

Tai Ping Che (太平車, lit. 'Peaceful cart')

Drawing of a Tai Ping Che (above) and its various components (below), from 'Zhan Shou Quan Shu (《戰守全書》)'.

Tai Ping Che is a mobile gun turret that can be lowered down the wall with a crane to attack enemy troops at the base of the wall.

For more details, please see my other post.

Meng Huo You Gui (猛火油櫃, lit. 'Fierce-fire oil cabinet')

Drawing of a Meng Huo You Gui, from 'Wu Bei Zhi (《武備志》)'.

Meng Huo You Gui is a double-piston pump naphta flamethrower with a gunpowder-based pilot flame torch. It is a defensive anti-personnel weapon, used to attack enemy troops at the base of the wall and clearing up siege trench.

Xing Lu (行爐, lit. 'Moving furnace')

Drawing of a Xing Lu, from 'Zhan Shou Quan Shu (《戰守全書》)'.

Xing Lu is a wooden cart with an on-board furnace used to prepare molten iron for siege defence. User of Xing Lu simply scoops up molten iron from the furnace, then sprinkles it down the wall. 

Yan Guan Hui Ping (煙罐灰瓶, lit. 'Smoke can and quicklime bottle')

Drawing of several containers for quicklime, from 'Wu Bei Ji Yao (《武備集要》)'.

Yan Guan Hui Ping is simply a ceramic container filled with powdered quicklime, a potent respiratory and blinding irritant that reacts violently with water, that can be thrown at the attackers at the base of the wall.

Shi Zha Pao (石炸砲, lit. 'Stone exploding bomb')

Shi Zha Pao of varying sizes discovered around the Great Wall.

Shi Zha Pao is a stone grenade that is essentially a combination of a rock and a bomb. It is usually thrown alongside ordinary rocks during siege, and can kill or cause severe injury with its weight alone. The explosion that came afterwards only serves to further increase its deadliness.

On top of its destructive potential, Shi Zha Pao also serves as a great psychological weapon. It punishes careless attackers that believe that a missed thrown rock no longer possess any danger, and goad enemy troops to be overly cautious against all thrown rocks, regardless of whether they really explode or not.

Shi Zha Pao can also be used as land mine.

Wei Yuan Shi Pao (威遠石砲, lit. 'Awe-inspiring long range stone cannon')

Drawing of a Wei Yuan Shi Pao with a long fuse that extends to the top of a wall, from 'Wu Bei Zhi (《武備志》)'.

Wei Yuan Shi Pao is a variant of Shi Zha Pao that is modified into a fougasse-like land mine/stone bombard. It is typically filled with gunpowder, pebbles and a stone cannonball, and must be manually activated by means of a fuse.

An unused Wei Yuan Shi Pao in Great Wall Museum, China.

Wei Yuan Shi Pao enjoys several advantages over a typical fougasse, namely it can be prefabricated and mass-produced, is deployable anywhere, is easily retrievable as well as reusable. Additionally, even if the stone casing fails and breaks apart during use, the stone fragments still add to the destructiveness of the explosion.

Other options

A row of landmines connected to a Gang Lun Fa Huo (鋼輪發火), from 'Wu Bei Zhi (《武備志》)'.

Many other weapons such as grenades and bombs, landmines, stakes, abatises, cheval de frise, caltrops, and various traps were also used to deter enemy assault. Due to constraint on the length of this article, they will not be covered in detail here.

4.2) Anti-siege tower

Xiang Mo Chu (降魔杵, lit. 'Demon-subduing pestle')

Drawing of a Xiang Mo Chu, from 'Jin Tang Jie Zhu Shi Er Chou (《金湯借箸十二籌》)'.

Xiang Mo Chu is a wall-mounted battering ram designed to destroy or otherwise prevent enemy siege towers from approaching.

Zhuang Che (撞車, lit. 'Ram cart')

Drawing of a Zhuang Che, from 'Wu Bei Zhi (《武備志》)'.

Essentially a mobile version of Xiang Mo Chu, Zhuang Che is a small battering ram designed to be driven up the wall to attack approaching scaling ladders and siege towers. Since it is a defensive weapon designed to be used on the wall, Zhuang Che relies on the wall itself for protection and does not need the protective canopy typical of most battering rams.

4.3) Anti-battering ram/siege gallery

Tie Ti Gou (鐵提鈎, lit. 'Iron lifting hook')

A battering ram in the town hall of Mercato San Severino, Italy. Note that if either of the two ropes (marked with red arrowheads) is cut, the battering ram will be rendered unusable immediately.

No matter the design, all battering rams share one critical weakness: the suspension ropes or chains that the log is hung on. Therefore, one of the easiest ways to disable a battering ram is to simply cut its suspension ropes.

Drawing of a Tie Ti Gou, from 'Wu Bei Zhi (《武備志》)'.

Tie Ti Gou is precisely the tool for such job. It is essentially a sharpened Gou Lian (鈎鐮) that allows its user to reach and cut the suspension ropes of approaching battering rams* from the top of a wall. It is also used to protect less robust fortifications, such as wooden palisades, from being torn down by grappling hooks.

*Note: It should be noted that battering rams were often mounted on siege towers to knock down battlement on the wall.

Chuan Huan (穿環, lit. 'Passing hoop')

Drawing of a Chuan Huan (highlighted), from 'Zhan Shou Quan Shu (《戰守全書》)'.

Chuan Huan is a type of simple but ingenious device used in siege defence to counter battering ram. It is basically a series of large iron hoops chained together with leather bands. During a siege, Chuan Huan can be lowered down the wall and around the log of a battering ram. After the battering ram is caught by one of the iron hoops, defenders on the wall can then pull up Chuan Huan again to disable or topple over the battering ram, and then use Meng Huo You Gui to set it on fire.

Tie Zhuang Mu (鐵撞木, lit. 'Iron ramming log')

A badly-drawn Tie Zhuang Mu (highlighted), from 'Wu Bei Zhi (《武備志》)'.

Tie Zhuang Mu is a wooden log fitted with a metal ram head with six large barbed spikes, dropped from a winch-operated crane to destroy or immobilise enemy battering rams. It is essentially a repurposed pile driver designed to give battering rams a taste of their own medicine.

Chong Mu (衝木, lit. 'Charging log')

Drawing of two Chong Mu (highlighted) one vertical and one horizontal, from 'Zhan Shou Quan Shu (《戰守全書》)'.

Chong Mu is essentially a guillotine blade used in siege defence. It serves the same purpose as Tie Zhuang Mu, i.e. to destroy enemy siege engines, in particular battering rams and siege galleries.

Fei Hu Quan (飛虎拳, lit. 'Flying tiger fist')

Drawing of a Fei Hu Quan, from 'Zhan Shou Quan Shu (《戰守全書》)'.

Fei Hu Quan, also known as Tie Ji Li (鐵蒺藜, lit. 'Punturevine', not to be confused with caltrop, which shares the same name), is a heavy spiked wrecking ball made of cast iron. It serves the same purpose as Tie Zhuang Mu.

Diao Dao (吊搗, lit. 'Hanging Thrasher')

Drawing of a Diao Dao, from 'Wu Bei Zhi (《武備志》)'.

Diao Dao is a giant grappling hook mounted on a simple wooden crane, designed to hook and topple over enemy siege engines.

Jiao Che (絞車, lit. 'Winch cart')

Drawing of a Jiao Che, from 'Wu Bei Zhi (《武備志》)'.

Jiao Che is a heavy wooden cart with a winch mounted on it. The winch is usually connected to a giant grappling hook so that the cart can serve as a mobile version of Diao Dao. However, whereas Diao Dao is designed to topple over enemy siege engines, Jiao Che aims to drag them directly over the wall and into the city/fortress.

Fei Ju (飛炬, lit. 'Flying torch')

Drawing of a Fei Ju, from 'Wu Bei Zhi (《武備志》)'.

Fei Ju is a wooden crane with a bundle of oil-soaked reed tied to its iron chain. It is designed to set fire on enemy siege engines that are already immobilised by Tie Zhuang Mu or through other means. The reed bundle, known as Yan Wei Ju (燕尾炬, lit. 'Swallowtail torch'), is intentionally shaped like a three-point star, so that it can "sit" on the gable-shaped canopy of a battering ram without sliding off.

Drawing of a Yan Wei Ju, from 'Wu Bei Zhi (《武備志》)'.

Tie Zhi Shen Che (鐵汁神車, lit. 'Iron liquid divine cart')

Drawing of a Tie Zhi Shen Che, from 'Zhan Shou Quan Shu (《戰守全書》)'.

Tie Zhi Shen Che is also a wooden cart with a small on-board furnace mounted on top. Unlike Xing Lu, Tie Zhi Shen Che has a treated bamboo pipe that allows its user to drip molten iron down the wall with more precision. It is specially designed to set fire to enemy siege engines.

Molten iron has several advantages over boiling water or oil when it comes to siege defence, namely it burns straight through normally fire resistant materials such as soaked cowhide, and creates enormous sparks upon hitting hard surface, potentially setting a very large area on fire. Nevertheless, molten iron is dangerous to handle and costly to prepare (iron only melts at high temperature so more fuel is required to prepare molten iron, fuel which could be on short supply during a siege), so this isn't a weapon that should be used lightly.

5) Firefighting

Although often overlooked, firefighting was one of the most important aspects of siege defence, as it was almost inevitable that something will catch fire during the chaos of battle. In addition to the typical axes, saws, shovels, hooks, buckets of water or sand and so on, Chinese people also made use of a variety of firefighting equipment for both siege defence and general firefighting during peacetime.

Various firefighting equipment, from 'Wu Bei Zhi (《武備志》)".

• Ji Tong (唧筒, lit. 'Pump'): A handheld water pump.
• Shui Dai (水袋, lit. 'Water bag'): A huge waterskin made of cow or horse hide. It is normally used in conjunction with a one zhang long bamboo pipe to put out fire from a safer distance.
• Shui Nang (水囊, lit. 'Water pouch'): A small pouch made of cow or pig bladder and filled with water. It is a throwable fire extinguisher (a primitive precursor of fire extinguishing grenade) that is primarily used to put out fire started by enemy sappers at the base of the wall.
• Ma Da (麻搭, lit. 'Hemp stroker'): A fire flapper made from a bundle of hemp tied to the end of a pole. It is usually drenched in mud or slurry before use.

Huo Lian (火鐮, lit. 'Fire sickle')

Drawing of a Huo Lian, from 'Wu Bei Zhi (《武備志》)'.

Huo Lian and its related cousins Huo Gou (火鈎, lit. 'Fire hook') and Huo Cha (火叉, lit. 'Fire fork') are several designs of firefighting pike poles used to tear down walls and other buildings to stop a fire's spread.

Liu Tong (溜筒, lit. 'Slip tube')

Drawing of a Liu Tong, from 'Fang Shou Ji Cheng (《防守集成》)'.

Liu Tong (not to be confused with the Chinese rocket launch tube, which shares the same name) is a simple bamboo water tank connected to an iron pipe. It can be used to put out fire started by enemy sappers at the base of the wall.

6) Water management

As with fire, water management was a very important but often overlooked aspect of siege warfare. Water was crucial for the survival of a fortress during siege, yet it could also spell doom if mishandled.

6.1) Protecting water supply

Water supply was key to the endurance of a garrison in time of war, and should be managed with utmost care. It was always preferable to have access to well protected water source, for example a water well built within the confines of a fortress, or a river that courses through a walled settlement. However, in the absence of such water source, the defenders must diligently protect the accessibility and safety of water sources outside the fortress against enemy blockade or intentional contamination. Most importantly, collecting water from outside the fortress must be conducted through sally port (or other concealed entrance) and never through the main gate of a fortress to avoid putting the safety of the fortress at risk.

6.2) Denying water supply to the enemy

On the flip side, denying local water supply to the enemy could potentially cut short the duration of their siege campaign drastically, thus increasing the odds of a successful defence. Before retreating into the fortress, the defenders ought to seek out and bury surrounding water wells that might be used by their enemy to the best of their ability, and poison other water sources that couldn't be buried.

6.3) Flood control

One major difference between pre-modern Chinese siege warfare and elsewhere is the frequent use of deliberate flooding attack, often through diverting a river, damming, or destroying an existing dam. In fact, there were probably more instances of deliberate flooding used in Chinese warfare than the rest of the world put together. 

Land survey equipment set that consists of a torpedo level (right), a leveling rod (not shown), and a handheld marker (to compensate for the lack of precision telescope, yet to be invented at the time) was frequently used in flooding attack.

Flooding tactics can be further divided into: submerging the target site underwater for weeks, months or even years (sometimes to the point of eroding away the fortification, causing subsequent flooding inside the target site. Both attackers and defenders might even resort to naval combat during the flood), storming flood that quickly "flush" the target site and everything in it, as well as flooding the surroundings of the target site (with siege moat or canal) to isolate the defenders, preventing them from seeking outside help. Such tactics were highly effective and nearly impossible to counter, but require major effort and time to pull off, not to mention destructive to the extreme, often causing unimaginable collateral damage in the process.

Illustrations depicting soldiers conducting land surveys to plan for a flooding attack, from 'Wu Bei Ji Yao (《武備集要》)'.

As mentioned before, it was nearly impossible to prevent a deliberate flooding attack. The best defenders could do were various reactive flood relief measures such as reinforcing the walls and gates, sealing leaks, controlled evacuation and relocating supplies, as well as maintaining and constructing flood drainage to reduce the damage of flooding. It was however possible for the defenders to sortie out during a flood (using boats) to sabotage the attackers' dam, turning the weapon against the attackers.

Deliberate flooding was sometimes used defensively as a last resort against an overwhelming attack.

7) Miscellaneous

7.1) Supplemental defensive equipment

Mu Man (木幔, lit. 'Wooden curtain')

Drawing of a Mu Man, from 'Wu Bei Zhi (《武備志》)'.

Mu Man is essentially the mobile version of Bu Man (布幔). It serves as a mobile protective screen that protects defenders on the wall from arrows, stones and other projectiles.

7.2) Breach response

Mu Nu Qiang (木女牆, lit. 'Wooden woman's wall')

Drawing of a Mu Nu Qiang, from 'Deng Tan Bi Jiu (《登壇必究》)'.

Mu Nu Qiang is a large prefabricated wooden shield installed on wheels. It is used as an emergency replacement for damaged battlement until said battlement can be repaired.

Sai Men Jia Qi Che (塞門架器車, lit. 'Gate-blocking weapon rack cart')

Drawing of a Sai Men Jia Qi Che, from 'Wu Bei Zhi (《武備志》)'.

Sai Men Jia Qi Che, commonly known as "Knife cart" in the West, is a huge wooden cart armed with four stacks of sharp implements as well as several guns. It is used as a last-ditch gate blockade in the case where the city gate is breached.

Yan Yue Cheng (偃月城, lit. 'Reclining moon wall')

Drawing of a Yan Yue Cheng, from 'Fang Shou Ji Cheng (《防守集成》)'.

Yan Yue Cheng is the Chinese term for coupure, i.e. a temporary wall hastily constructed to seal off a damaged or breached wall section from the inside, in the case that the defenders fail to repair the damaged wall in time. It essentially turns the breach into a death trap akin to Weng Cheng (甕城).

Xiang Zhan Che (巷戰車, lit. 'Alley-combat cart')

Drawing of a Xiang Zhan Che, from 'Wu Jing Zong Yao (《武經總要》'.

Xiang Zhan Che is an armed wheelbarrow or cart used to blockade an alleyway. It is only used when the wall is breached and the siege defence has deteriorated to the point where the defenders have to resort to urban warfare to repulse the attackers.

7.3) Mobility equipment

Diao Che (吊車, lit. 'Crane')

Drawing of a Diao Che, from 'Wu Bei Zhi (《武備志》)'.

Diao Che, also called Xia Cheng Jiao Che (下城絞車, lit. 'City-descending winch cart'), is a winch-driven lift mounted on the wall. It can be used to send scouts, messengers, and saboteurs out of the city in secret, or receive stranded or injured refugees without having to reopen the city gate.

Sheng Ti (繩梯, lit. 'Rope ladder')

Drawing of a rope ladder, from 'Fang Shou Ji Cheng (《防守集成》)'.

Sheng Ti is a heavy rope ladder that is more convenient than Diao Che but serves largely the same purpose. Unlike Diao Che, it cannot be used to receive injured refugees or refugees bringing children or other heavy luggage.

Fei Qiao (飛橋, lit. 'Flying bridge')

Layout of a small fortress with interconnecting rooftop bridges, from 'Zhan Shou Quan Shu (《戰守全書》)'.

Fei Qiao is simply a rooftop bridge connecting one building to another or to the top of a wall, which allows defending troops to move around the fortress quickly to reinforce a wall section currently under attack. It also allows the defenders to rig the ward (bailey) of a fortress in traps and landmines then lure the enemy inside, without risking themselves in the process.