Chapter 62: Preparations Against Tunneling
Qinzi bowed twice and said, “May I ask, if the ancients who were skilled at attacking cities dug tunnels to enter, tied wooden posts, and set fire to them to destroy our city walls, and when the walls collapsed, the defenders were caught in the middle, what should be done?”
Master Mo said, “Are you asking about defending against tunneling? To prepare against tunnels, build high towers inside the city to carefully watch the enemy. If the enemy changes their wall-building and earth-piling methods, or if the Peng River water becomes abnormally turbid, this indicates tunneling. Quickly dig trenches inside the city, and dig toward the enemy’s tunnel direction. Dig wells inside the city, one well every five bu, close to the city wall base. In high ground, dig fifteen chi deep; in low ground, stop three chi below the water table. Have potters make large earthen jars (Ying) with a capacity of over forty dou, cover the mouth with thin leather, and place them in the wells. Have people with sharp hearing lie on the jars to listen, accurately determine the enemy tunnel’s location, and dig to intercept it.
Have potters make ‘Yue Ming’ (half-round ceramic pipes), two chi five cun long and six wei in circumference, split in the middle, joined and placed in the tunnel, one concave and one convex. Smear the outside of the posts well, do not burn near the posts. Smear the joints of the posts well, do not let smoke leak. Do the same on both sides, advancing with the tunnel. When close to the ground, place chaff or ash inside, do not fill completely. Ash and chaff should be five dou long, mixed left and right, evenly distributed. Build a stove at the tunnel entrance like a kiln, capable of holding seven or eight bundles of mugwort, with the same setup on both side tunnels, using four bellows. When the tunnel is about to meet the enemy, use a Jie Gao (ramming tool) to strike, quickly pump the bellows to smoke them out. Must have skilled bellows operators at the stove mouth, do not let them leave.
Use connected boards (Lian Ban) made according to the tunnel’s height and width, let the diggers advance with the boards. Pierce the boards to allow spears to protrude, with one-third spacing, to rescue the smoke tunnels. When tunnels meet, use boards to block, use spears to rescue smoke tunnels, do not let them be blocked; if blocked, pull back the boards, pass one smoke tunnel and block again, pierce the tunnel, let smoke through, then quickly pump bellows to smoke. Listen to the enemy’s left and right from inside the tunnel, urgently cut off their front, do not let them advance. If the enemy gathers in the tunnel, block with firewood, smear with mud, so they cannot burn the boards. Thus, the tunnel attack is defeated.
When the enemy arrives, it is urgent, carefully prepare against tunnels. If suspected, respond urgently. If no tunnel is found, do not pursue blindly.
To kill tunnel attackers, set up a position every twenty bu, tunnel ten chi high, dig ten chi deep, as before, three chi down per bu, build a defensive point every ten bu, horizontal passage left and right, ten chi high and wide.
In the defensive point, place two large jars, level with the city wall, place boards on top, use the covering boards to listen in the well. One dense point every five bu, use Tai or pine wood for the tunnel door, with two caltrops, length equal to the door. Set a ring on the door, build stone outer wall seven chi high, add parapets on top. Do not build steps or stones, use suspended ladders for entry and exit. Prepare furnaces and bellows, bellows made of cowhide, furnace has two jars, use a bridge to pump, each time smoke forty shi, smolder charcoal, fill furnace and cover, do not let gas escape. If the enemy is within five hundred bu, and their tunnel is higher or lower, not reaching ours, dig upward or downward to break through and connect. When meeting the enemy in the tunnel, defend and do not pursue, fight and retreat, wait for the furnace fire to ignite, then retreat into the defensive point.
In the defensive point, there are rat holes (small passages), with doors and locks, allowing solo passage. Keep a dog in each tunnel and fortress; if the dog barks, someone is there.
Cut mugwort and firewood one chi long, place in the kiln, first build kiln walls, build connected walls toward the tunnel. Dig wells at the city wall base, one every three zhang, determine well position based on external width, do not make mistakes. If the city is low and the tunnel is high, attacking from the tunnel is difficult. Dig wells on the city wall, three or four wells, put new jars inside, lie down to listen. Accurately determine the tunnel location, dig to intercept. When about to meet, make Jie Gao, must use hard wood for the pole, attach sharp axes, order three strong men to ram with Jie Gao, pour over ten shi of filthy water. Quickly lie in this well, place mugwort on top, in seven portions, cover the well mouth with a basin, do not let smoke leak upward, attach bellows to the side, quickly pump.
Use cart wheels as cover. Bundle firewood, smear with mud and bind with hemp rope. Use iron chains, three zhang long, one end a ring, one end a hook, hang directly at the enemy tunnel mouth.
Tunnel height seven chi five cun, width between posts one chi, one post every two chi, posts rest on wooden pads, two posts share one round timber. Two posts of the same material, horizontal round timber also. Post circumference two and a half wei, must secure the round timber well, do not let posts intersect.
Two kilns in the tunnel, both with Yue houses, one official and one attendant each, must have water. Block the tunnel door, use two cart wheels as screens, smear with mud, according to tunnel height and width, let people enter four or five chi, secure with ropes. When the enemy rushes the door, turn the screen to block. Build a kiln to hold three bundles of mugwort, let ambushers rush in. Ambushers stick to one side of the rush door, guard with two bellows, do not leave. Tunnel spears are iron, four and a half chi long, size like iron armor, i.e., two bladed spears. One chi from the smoke tunnel, dig diagonally, at the tunnel center, spear seven chi long. Set up Huan Lv rates (tools) in the tunnel, two in the tunnel.
Dig wells on the city wall, when the well is about to connect, stand on a board, dig one side, then move the board, dig the other side. Jie Gao has two poles, bury posts on the sides, hook both ends multiple times. Fifty people dig tunnels, half men and half women. Fifty people.
The attacker builds a passage inside, holds six can, tie with hemp rope below, can be lifted and thrown. After digging, seven people guard the retreat fortress, build a large corridor, hide tunnel tools inside. When tunneling is difficult, take wood from the moat edge, cut the tunnel, deep to the spring. When hard to approach, make iron tools, gold and Fu Lin four chi long, sufficient for the task. If the enemy tunnels, also tunnel to respond.
Make iron hooks four chi long, sufficient for the task, when tunnel connects, use to hook the enemy tunnel. Make short spears, short crossbows, Meng arrows, sufficient for the task, use to fight when tunnel connects. Use metal swords for difficult situations, five chi long, with socket and wooden handle, handle has Lü Mei, to deal with enemy tunnels.
Alert with jars, capacity over thirty dou, bury in the tunnel, one per zhang, to listen to tunnel sounds.
Dig tunnels, eight chi high, wide, arrange well. Prepare Quan, Niu Jiao Gao, and tile jars, guard two tunnels, cover with Chen Huo and mugwort, smoke when tunnel connects.
Use axe metal for chopping, handle three chi long, guard four tunnels. Build fortresses, guard forty tunnels, four attached. Prepare adzes, axes, saws, chisels, hoes, sufficient for the task. Make iron grilles, guard four tunnels.
Build a central Lu (shelter), ten and a half zhang high, four chi wide. Build eight horizontal tunnel Lu covers. Prepare Gao Xi, sufficient for the task, to illuminate the tunnel.
Cover with vinegar, if the enemy smokes, use to save eyes. To save eyes, dig tunnels in different directions, place vinegar in the tunnel, Wen basins no less than four dou. If smoked, apply to eyes and wash.”
Note
This chapter details Mohist counter-tunnel tactics. It uses leather-covered jars to detect digging sounds, dig intercepting tunnels, and deploy mugwort smoke, spears and vinegar to defeat underground enemy assaults.
Qin Guli (禽滑厘):
Also known as Qinzi, Qin Huali, he was Mozi’s most prominent disciple and the primary interlocutor in the military chapters of the Mozi. His questions demonstrate the practical, field-tested nature of Mohist defensive doctrines.
Acoustic Detection (Listening Jars / 罂听):
One of the most fascinating ancient acoustic surveillance techniques. By placing large, leather-sealed earthen jars in wells along the city wall, defenders could use the jars as acoustic resonators. A person with sharp hearing lying on the jar could detect the faint sounds of enemy digging and pinpoint the exact direction of the tunnel. This is an early application of acoustic resonance in warfare.
Counter-Tunnel Warfare:
Tunnel warfare was a major siege tactic in ancient China. Attackers would dig under walls and burn wooden supports to collapse them. The Mohists developed a comprehensive counter-strategy: acoustic detection, digging intercepting tunnels, and using smoke, fire, and water to neutralize the enemy in confined underground spaces.
Chemical & Smoke Warfare:
The text details the use of mugwort, charcoal, and even “filthy water” combined with bellows to create toxic, suffocating smoke. The mention of using vinegar to wash eyes affected by smoke shows an early understanding of chemical irritants and first aid.
Tunnel Architecture:
The Mohists engineered specialized underground structures, including half-round ceramic pipes for ventilation and smoke channeling, iron hooks for grappling in dark tunnels, and specialized iron-tipped spears designed for close-quarters underground combat.
Jie Gao (颉皋):
A specialized ramming or striking tool used in confined tunnel spaces to break through enemy barricades or collapse tunnel supports.
Yue Ming (月明):
Literally “moonlight,” this term refers to the half-round ceramic pipes used to line tunnels. The name likely derives from their crescent shape when joined together.
Peng River (彭水):
A reference to a specific geographical location, indicating that Mozi’s teachings were often tailored to specific regional terrains and water systems relevant to the states involved in the conflicts.
禽子再拜再拜曰：“敢问古人有善攻者，穴土而入，缚柱施火，以坏吾城，城坏，或中人为之奈何？”
子墨子曰：问穴土之守邪？备穴者城内为高楼，以谨候望适人。适人为变筑垣聚土非常者，若彭有水浊非常者，此穴土也。急堑城内，穴其土直之。穿井城内，五步一井，傅城足。高地，丈五尺，下地，得泉三尺而止。令陶者为罂，容四十斗以上，固顺之以薄靼革，置井中，使聪耳者伏罂而听之，审知穴之所在，凿穴迎之。
令陶者为月明，长二尺五寸六围，中判之，合而施之穴中，偃一，覆一。柱之外善周涂，其傅柱者勿烧。柱者勿烧。柱善涂其窦际，勿令泄。两旁皆如此，与穴俱前。下迫地，置康若灰其中，勿满。灰康长五窦，左右俱杂，相如也。穴内口为灶令如窑，令容七八员艾，左右窦皆如此，灶用四橐。穴且遇，以颉皋冲之，疾鼓橐熏之，必令明习橐事者，勿令离灶口。连版，以穴高下，广陕为度，令穴者与版俱前，凿其版令容矛，参分其疏数，令可以救窦。穴则遇，以版当之，以矛救窦，勿令塞窦；窦则塞，引版而却，过一窦而塞之，凿其窦，通其烟，烟通，疾鼓橐以熏之。从穴内听穴之左右，急绝其前，勿令得行。若集客穴，塞之以柴，涂，令无可烧版也。然则穴土之攻败矣。
寇至吾城，急非常也，谨备穴。穴疑有，应寇，急穴。穴未得，慎毋追。
凡杀以穴攻者，二十步一置穴，穴高十尺，凿十尺，凿如前，步下三尺，十步拥穴，左右横行，高广各十尺。
杀，俚两罂，深平城，置板其上，册板以井听。五步一密，用枱若松为穴户，户穴有两蒺藜，皆长极其户，户为环，垒石外郭，高七尺，加堞其上。勿为陛与石，以县陛上下出入，具炉橐，橐以牛皮，炉有两缻，以桥鼓之，百十每亦熏四十什，然炭杜之，满炉而盖之，毋令气出。适人疾近五百穴，穴高若下，不至吾穴，即以伯凿而求通之。穴中与适人遇，则皆圉而毋逐，且战北，以须炉火之然也，即去而入壅穴。
杀，有鼠穴，为之户及关籥独顺，得往来行其中。穴垒之中各一狗，狗吠即有人也。
斩艾与柴长尺，乃置窑灶中，先垒窑壁，迎穴为连。凿井傅城足，三丈一，视外之广陕而为凿井，慎勿失。城卑穴高从穴难。凿井城上，为三四井，内新甀井中，伏而听之。审之知穴之所在，穴而迎之。穴且遇，为颉皋，必以坚材为夫，以利斧施之，命有力者三人用颉皋冲之，灌以不洁十余石。趣伏此井中，置艾其上，七分，盆盖井口，毋令烟上泄，旁其橐口，疾鼓之。
以车轮辒。束樵，染麻索涂中以束之。铁锁，县正当寇穴口。铁锁长三丈，端环，一端钩。
𠏙穴高七尺五寸，广柱间也尺，二尺一柱，柱下傅舄，二柱共一员十一。两柱同质，横员士。柱大二围半，必固其员士，无柱与柱交者。
穴二窑，皆为穴月屋，为置吏、舍人各一人，必置水。塞穴门，以车两走为蒀，涂其上，以穴高下广陕为度，令人穴中四五尺，维置之。当穴者客争伏门，转而塞之。为窑容三员艾者，令其突入伏。伏傅突一旁，以二橐守之勿离。穴矛以铁，长四尺半，大如铁服说，即刃之二矛。内去窦尺，邪凿之，上穴当心，其矛长七尺。穴中为环利率，穴二。
凿井城上，俟其身井且通，居版上，而凿其一偏，已而移版，凿一徧。颉皋为两夫，而旁貍其植，而数钩其两端。诸作穴者五十人，男女相半。五十人。攻内为传士之口，受六参，约枲绳以牛其下，可提而与投。已则穴七人守退垒之中，为大庑一，藏穴具其中。难穴，取城外池唇木月散之什，斩其穴，深到泉，难近穴，为铁 ，金与扶林长四尺，财自足。客即穴，亦穴而应之。
为铁钩钜长四尺者，财自足，穴彻，以钩客穴者。为短矛、短驽、 䖟矢，财自足，穴彻以斗。以金剑为难，长五尺，为銎、木杘；杘有虑枚，以左客穴。
戒持罂，容三十斗以上，貍穴中，丈一，以听穴者声。
为穴，高八尺，广，善为傅置。具全、牛交槀及瓦缶，卫穴二，盖陈靃及艾，穴彻熏之。
斧金为斫，杘长三尺，卫穴四。为垒，卫穴四十，属四。为斤、斧、锯、凿、䦆，财自足。为铁校，卫穴四。
为中橹，高十丈半，广四尺。为横穴八橹盖。具槀枲，财自足，以烛穴中。
盖持醯，客即熏，以救目。救目分方凿穴，以益盛醯置穴中，文盆毋少四斗。即熏，以自临上及以沺目。”
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