The Fifty-Fifth Method of Defending a City

城不守者：大而人少；小而人眾；糧寬而柴水不供；壘薄而攻具不足；土疏地下，溉灌可設；人戶疲悴，修緝未就。凡此類者，速徒之。營壘高厚，城堅溝深，糧食眾多，地利險阻，所謂無守無不守也。故曰：善守者，敵不知其所攻。

There are several types of cities that are difficult to defend: large cities with few people, where the military forces cannot be spread out effectively; small cities with many people, where overcrowding occurs and food supplies are quickly consumed; cities where there is enough grain but not enough firewood and water; cities with weak fortifications and insufficient defensive equipment; and cities with loose soil and low-lying terrain, which can be flooded by the enemy. If a city falls into any of these categories, it should be evacuated as soon as possible. In contrast, if the fortifications are high and thick, the city walls are strong, the moats are deep and wide, the food supplies are abundant, and the city occupies a strategic and difficult-to-reach location, then it is said to be "without a specific place to defend, yet able to defend everywhere." Therefore, the "Art of War" by Sun Tzu says: A skilled defender makes it impossible for the enemy to know where to attack.

凡築城，下闊與高倍，上闊與下倍。城高五丈，下闊二丈五尺，上闊一丈二尺五寸。高下闊狹，以此為準。料工：上闊下加闊，得三丈七尺五寸；半之，得一丈八尺七寸五分；以高五丈乘之，一尺之城積數〈積數一作利〉得九十三丈七尺五寸。

Whenever a city is built, the bottom width is half the height of the city, and the top width is half the bottom width. If the city is five zhang high, then the bottom width is twenty-five chi, and the top width is twelve chi and five cun. Regardless of the height and width of the city, this proportion is used. The method for calculating the earthwork volume is: add the top width and the bottom width, resulting in thirty-seven chi and five cun; take half of this, resulting in eighteen chi and seven cun and five fen; then multiply this by the height of five zhang. Thus, for each chi of length of the city wall, the volume of earth is ninety-three zhang, seven chi, and five cun (the term 'accumulated number' is sometimes written as 'accumulated profit').

每一工，舊築土二丈，計工約四十七人。一步五尺之城，計役二百三十五人。百步之城，計工二萬三千五百人。三百六〈一作九〉十步，計工八萬四千六百人。率一里，則十里可知也。其出土負簣，並計之於工內矣。城內面，別穿井四所，置水車大甕二十口，灶千所。卻敵臺上建候樓，以跳板出為櫓，與四外烽戍晝夜瞻視，以備警急。

According to the old practice, each laborer could build two zhang of earthwork, so a wall one chi long would require forty-seven laborers. A wall one bu long (five chi) would require two hundred and thirty-five laborers; a wall one hundred bu long would require twenty-three thousand five hundred laborers; a wall three hundred and sixty bu long (the text says 'six' but some versions say 'nine') would require eighty-four thousand six hundred laborers. This is the number of laborers required for one li. The number for ten li can be calculated accordingly. The labor required for digging and carrying earth is already included in the total. Inside the city, four wells were dug, along with twenty water wheels and large jars, and one thousand cooking stoves. On the 'enemy platforms' (protruding towers outside the walls), watchtowers were built, with planks projecting outward to serve as 'lookout towers' (open observation platforms), which communicated with the watchtowers in all directions day and night to guard against sudden emergencies.

鑿壕之法，面闊二丈，深一丈，底闊一丈。以面闊二丈加底闊一丈，積數大半得之，得數一丈五尺。以深一丈乘之，鑿壕一丈，得數一十五丈。每工日出三丈，計工五人。一步五尺，計工二十五人。十步，計工二百五十人。百步，計工二千五百人。三百六十步，計工九千人。率一里，則百里可知也。

The specifications for digging a moat: the width at the top is two zhang, the depth is one zhang, and the width at the bottom is one zhang. Adding the width at the top (two zhang) and the width at the bottom (one zhang), take half of this sum, which is one and a half zhang, as the average width. Multiply this by the depth of one zhang, resulting in fifteen zhang of earth removed for every zhang of moat length. Each worker can remove three zhang of earth per day, so one zhang of moat requires five workers. For one step (equivalent to five chi), it requires twenty-five workers; for ten steps, two hundred and fifty workers; for one hundred steps, two thousand five hundred workers; and for three hundred and sixty steps, nine thousand workers. This is the number of workers required for one li. The number of workers needed for one hundred li can be calculated in the same way.

城上一步〈一作裡〉一甲卒，十步加五人，以備雜供之要。五步有五長，十步有十長，五十步、百步皆有將長。文武相兼，量才授任，而統領精銳驍勇，或十隊，或二十隊，三十隊。大將、副將各〈一作為〉領隊巡城，曉諭激勸赴役。

On the city walls, one armored soldier was assigned for each step (the term "step" in some editions reads "li"), and five additional soldiers were assigned every ten steps to handle various miscellaneous tasks and supplies. At every five steps, a "Five-Commander" was stationed, and at every ten steps, a "Ten-Commander" was stationed. At fifty and one hundred steps, commanders known as "General Commanders" were stationed. Soldiers should be selected with both literary and martial abilities in mind, and assigned positions according to their talents. These commanders led elite and courageous units, either ten, twenty, or thirty squads. The main general and deputy general each led their respective squads to inspect the city defenses, announce orders, and encourage the soldiers to perform their duties bravely.

城上分四隊，別立四表以為攻城之候焉。若敵欲攻之處，去城五六十步，即舉一表；撞梯逼城，舉二表；敵若登梯，舉三表；欲攀女墻，舉四表。夜則舉火如表法。

The city walls were divided into four squads, each establishing four kinds of "tables" (signal markers) to report the progress of the enemy's attack. When the enemy was about to attack, and they were still fifty to sixty paces away from the city, one table was raised. When the ramming towers and ladders approached close to the city walls, two tables were raised. When the enemy began climbing the ladders, three tables were raised. When they were almost reaching the parapet, four tables were raised. At night, fires were used instead of tables, with the same number of fires as the number of tables raised during the day.

城上四隊之間，各〈一作為〉置八旗。若須水摽、枋板，舉蒼旗；須灰炭、銅鐵，舉赤旗；須礧木、樵葦，舉黃旗；須砂石、磚瓦，舉白旗；須水湯不潔之物，舉黑旗；須毛氈、麻䌇、鑠鐵、鍬鑊、斧鑿，舉雙兔旗；須戰士銳卒，舉熊虎旗；須戈戟矢弓刀劍，舉鷙旗。當主之官，隨色而供。城內老少婦女除營食外，皆令應役於城上，分為八隊，使識文字者點檢常旗物與八部也。

Between the four squadrons on the city walls, eight flags were set up for signaling the need for supplies. If water markers and wooden boards were needed, a green flag was raised; if lime and metal were needed, a red flag was raised; if stone balls and straw reeds were needed, a yellow flag was raised; if sand and bricks were needed, a white flag was raised; if boiling water and dirty substances were needed to scald the enemy climbing the walls, a black flag was raised; if woolen felt, hemp rope, molten iron, shovels, hoes, axes, and chisels were needed, a double rabbit flag was raised; if soldiers and reinforcements were needed, a bear and tiger flag was raised; if spears, halberds, arrows, bows, swords, and daggers were needed, a predatory bird flag was raised. Officials in charge of various supplies provided the needed items according to the color of the flag. All the old men, women, and children in the city, except those responsible for cooking and feeding, were required to serve on the walls, organized into eight squads. Literate individuals were assigned to count and verify the items corresponding to each flag, and to supervise these eight squads.

我城若居卑下之地，敵人擁水灌城，速築墻壅諸門及陷處。更於城內促為周匝，視水高下狹闊，築墻，外取土高一丈以上。城立，於墻外取土而薄築之。精兵備守，不得容雜色人。

If our city is located in a low-lying area and the enemy floods the city by blocking the water, we must quickly build walls to block all city gates and low-lying areas. Then, urgently construct a circular wall around the city, determining the scale of the wall based on the water level and the width of the water surface. Take soil from outside the wall to build it higher than one zhang. After the wall is built, continue taking soil from outside to add another thin layer for reinforcement. Assign elite soldiers to guard this area and prohibit any unauthorised persons from entering.

如有洩水之處，則十步為一井，井內潛通引洩漏。城中速造船一二十隻，募解舟楫者，載以弓弩鍬釒瞿，每三十人自暗門穴銜枚而出，決其堤堰。敵覺，即急於城上鼓譟，以精銳急出助之。

If a drainage outlet can be found, dig a well every ten steps, and connect the wells underground to drain away the accumulated water. In the city, quickly build about twenty boats, recruit people skilled in rowing, and equip them with bows and arrows, as well as shovels and picks. Send each group of thirty people through the secret entrance, with a mouth gag, to break through the embankments built by the enemy. Once the enemy becomes aware, immediately beat the drums and shout from the city walls, and dispatch elite troops to reinforce them quickly.

高下與城等，去城百步，每臺相去亦如之。下闊四丈，高五丈，上闊二丈。上建女墻，內通暗道，安屈膝梯，人上便卷收之。中設氈幕，置弩手五人，備糧水火。

The height of the弩台 is equal to that of the city wall, located 100 steps away from the wall. The distance between each弩台 is also 100 steps. The base of each弩台 is 40 feet wide and 50 feet high, with the top 20 feet wide. A parapet is built on top of the platform, and there is an underground passage inside the platform. A "bent-leg ladder" (a collapsible soft ladder) is set up, which can be folded and stored. After people climb up, the ladder is immediately rolled up. A tent is set up on top of the platform, with five archers stationed there, and sufficient food, water, and firewood are provided.

高山四顧險絕處置之，無山亦於孤回平地置之。築羊馬城，高低便常以三十五為堆。臺高五丈，下闊二丈，上闊一丈，形圓。上建圓屋覆之。屋徑有六尺，一面跳出三尺，以板為之上覆下棧屋。上置突灶三所，臺下亦置三所，並以石灰飾其表裡。

The beacon towers should be built on high mountains where they can be seen from all directions and the terrain is extremely dangerous and strategic. If there are no mountains, they should be placed on flat ground where they stand alone and are surrounded by open, circular areas. Outside the base of the tower, a small protective wall called "Yangma City" should be constructed, with its height and thickness determined by practical needs, usually built in layers according to the number thirty-five. The tower itself should be five zhang high, with a base width of two zhang and a top width of one zhang, shaped circularly. On top of the tower, a round building should be constructed to cover the tower's surface, with a diameter of six chi. One side of the building should extend outward by three chi, made of wooden planks, with a roof above and a wooden platform below. Three "tuzao" (smoke-emitting chimneys) should be set up on top of the tower and three more below, with both inner and outer surfaces coated with lime.

復置柴籠三所，流火繩三條，在臺側近。上下用屈膝梯，上訖收之。屋四壁開睹賊孔及安視火筒。置旗二口，鼓一面，弩兩張，礟石，礨木，停水甕，乾糧，麻熅，火鉆，火箭，蒿艾，狼糞。

Near the platform, three "chailong" (bundles of firewood used to signal by lighting and raising them) and three "liuhuoseng" (continuous fire ropes for passing signals) should be set up. A knee-length ladder is used to go up and down the platform, which is then folded away once on top. There are observation holes in the walls of the building, and "shihuo tong" (tubes for viewing fire signals from adjacent platforms) are installed. On the platform, there are two flags, one drum, two crossbows, as well as stone projectiles, wooden logs, water containers, dry food, hemp fiber (for starting fires), fire drills, fire arrows, wormwood, and wolf dung (which produces smoke when burned, known as wolf smoke).

每晨及夜平安，舉一火；聞警覺，舉二火；見煙塵，舉三火。見賊，燒柴籠。如每晨及夜平安，火不來，即烽子為人所捉。一烽六人，五人為烽子，遞知更刻，觀視動靜；一人為烽師，知文書符牒轉遞。

Every morning and at nightfall, a single torch is lit to signal peace. If an alarm is heard, two torches are lit. If smoke is seen, three torches are lit. If enemies are actually sighted, then a bundle of firewood is burned. If at the time of morning or nightfall when a peace signal should be sent, the fire signal from the neighboring beacon tower does not arrive, it means that the 'beacon soldier' there has been captured by the enemy. Each beacon tower is staffed by six people: five are 'beacon soldiers' who take turns keeping watch and observing the situation, and one is the 'beacon officer' who is responsible for transmitting official documents and messages.

牙帳前立百尺竿，上置板屋，四面開門，狀如斗。令人上望賊，賊有所攻，隨其方面以小白旗招之。眾賊往來，聚散遠近，皆審而觀之，以告於下。

At the main general's headquarters, a pole of a hundred feet high was erected in front. At the top of the pole, a small room made of boards was placed, with doors on all four sides, resembling a square bucket. People were sent up to observe the enemy's movements: whenever the enemy attacked from a certain direction, a small white flag was waved in that direction as an alarm. The movements, gathering and dispersing, and the distance of the enemy troops were all carefully observed, and the information was reported to the people below in real time.

每鋪相去三十里，於要路山谷間牧馬兩匹，設游奕計會。有事警急，煙塵入境，即報探。設土河於山谷口，當賊路橫斷，闊二丈，深二尺，以細沙土填平。每日檢行跡，掃令凈平。人馬入境，即知足跡多少。

The horse pastures are thirty li apart, located on the main road and in the valley, where two horses are kept for herding. They work together with the patrol riders called "youyi" to exchange information. Once an alarm is raised, and enemy smoke and dust enter the territory, they immediately report the information they have gathered. At the entrance of the valley, a "tuhuo" is built: a ditch is dug across the enemy's path, two zhang wide and two chi deep, filled with fine sand soil. Every day, the surface is checked for tracks, swept clean and level. In this way, whenever people and horses enter the territory, the number can be determined by looking at the footprints.

軍中選驍勇諳山川泉井者充之，常與土河、烽、鋪計會交牌。日夕邏候於亭障之外，捉生事問。其軍中虛實體用，勿使游奕人知。其副使子將並用久在軍中行人〈一作善〉騎射者充之。

"Yoyi" are selected from the military for their bravery and familiarity with mountain ranges and the locations of springs and wells. They frequently exchange messages and credentials with the Tuhuo, beacon towers, and horse stations. They patrol and scout outside the border outposts day and night, capturing live prisoners to interrogate and learn about enemy situations. As for the military's actual strength and deployments, they should not be made known to the Yoyi personnel, to prevent leaks if they are captured. The deputy and subordinates of the Yoyi should be appointed from those who have long served in the military and are skilled in horseback riding and shooting ("renxun" in one edition reads "shàn").

雜物，守城之時，其什物、五穀、糗糒、魚鹽、布帛、醫藥、工巧戎具、鍛冶、稭稿、茆荻、蘆葦、灰炭、柴薪、松樺、蒿艾、脂臈、麻皮、氈毯、荊棘、篦籬、釜鑊、盆甕、礨木、槌、鑿刀、鋸、長斧、長刀〈一作矛〉、長錐、長梯、短梯、大鉤、連鎖，但人所用之物，一一預備。仍令修緝，不得損壞。

First, we discuss 「miscellaneous items」. When defending the city, all kinds of tools, five grains, dried grain and fried millet, fish and salt, cloth and silk, medicine, the skills of craftsmen, weapons, and tools for forging and smelting, straw, reed grass, rush, reeds, ash and charcoal, firewood, pine and birch wood, wormwood and mugwort, oil and wax candles, hemp skin, felt and rugs, thorny bushes, bamboo and willow hurdles (used to block arrows), pots and cauldrons, basins and jars, siege ladders, hammers, chisels, axes, long axes, long spears (in some versions, it is written as 「矛」, spear), long spears, short ladders, large hooks, and chains, all things that people may need, should be prepared one by one in advance; and they should be constantly repaired and maintained, and no damage is allowed.

雜備，上八隊之間安轉關小炮〈一作仉〉二，機關大炮一。雲梯撞炮等間。先從城身用木跳出為重女墻，高於土女墻五寸以上，以板覆之，隨事緩急而開閉之。敵若以大石擊墻樓，石下之處，出跳空中，懸生牛皮或氈毯等袋，以乘其石。

Now regarding "za bei" (miscellaneous equipment). Between the eight squads on the city walls, two small torsion catapults capable of turning are placed, along with one large torsion catapult equipped with a mechanism, to deal with ladders and ramming vehicles. The necessary tools for countering these are also arranged among them. First, wooden structures are extended outward from the city walls to form a second layer of parapet, which is higher than the original earth parapet by more than five inches. Boards are placed over the top, which can be opened or closed according to the situation. If enemies throw large stones at the parapet, wooden frames are extended upward from the point where the stones fall, with sacks made of raw cowhide or felt hung from them to catch the stones and reduce their impact.

城內人家，咸令置水防火，先約〈先一作但〉失火者斬。火發之處，多恐奸人放火，但令近便主當八部官人領老少婦女救之。火起所部，急白大將，大將親領信人、左右救火。城中有卒警及雜人，城上不得輒離職掌，亂走街巷。違者斬之。敵若推輪排來攻，先以手炮打，手炮既眾，所中傷必多。來者被傷，則力不齊矣。

Within the city, every household must store water for fire prevention and agree in advance that those who start a fire will be executed. When a fire breaks out, it is often suspected to be set by spies, so only the nearby eight officials in charge and the elderly, women, and children are allowed to go out to fight the fire. The department responsible for the fire must quickly report to the commander, who personally leads reliable men and his attendants to put out the fire. If there is any sudden alarm or suspicious people causing unrest within the city, the guards on the city walls must not leave their posts or run around the streets; anyone who does will be executed. If the enemy attacks with a wheeled shield wall, they should first be attacked with hand-fired projectiles (stones or fire weapons). If many hand-fired projectiles are launched and hit, many enemies will be wounded, and their attacking strength will be greatly reduced.

懸門，懸板為門也。鐵甘之如棧板，用之懸鐘，板繞城於敵柵上，上皆懸板。受敵之時，則板起發矢。突門，於城中對敵營自鑿內為暗道，多少臨時，入五六寸，力穿。或於中夜，於敵初來營則未定，精騎從突門躍出，擊其不意。塗扇，以泥泥城門，可厚三尺，備火。鑿門，為敵所逼，先自鑿門扇十數孔，出弩射之，長矛剌之，敵且不得近。門棧塗，以泥塗門上大棧，可厚五寸，備火。

"The 'suspended door' refers to using a suspended wooden board as a door. The board is covered with iron and made like a stack board, and it is lifted using a method similar to that of a hanging bell. These boards are arranged along the city wall facing the enemy's fortifications. When under attack, the boards are raised, allowing arrows to be shot from below. The 'sudden door' is a secret passage dug from inside the city in the direction facing the enemy's camp. Several such passages are dug in advance, each dug about five or six inches deep, and when needed, they are forcefully broken through. Alternatively, during the night, when the enemy has just arrived and their camp is not yet secure, elite cavalry can leap out from the sudden door to attack them by surprise. The 'mud-covered door' involves coating the door of the city wall with mud, up to a thickness of three feet, to resist fire. The 'drilled door' is used when the enemy approaches the city gate. Beforehand, several holes are drilled into the city gate's door, through which arrows are shot or long spears are thrust, preventing the enemy from getting close. The 'mud-coated door frame' involves coating the large wooden boards above the city gate with mud, up to a thickness of five inches, serving the same purpose of fire resistance."

篦籬戰格，於女墻上跳出，椽去墻三尺，橫者檢。椽安轄，以荊柳編之，長二尺，闊五尺，懸椽端，以遮矢石。布幔，以復布為幔，用弱竿懸倒於女墻外，去墻七八尺，柔石之勢，則矢石不復近墻矣。連梃，如打禾連枷狀，打女墻外上城人。叉竿，如槍刃，為兩歧，用叉飛梯及人。鉤竿，如槍刃，偏有曲，可以鉤人。

"The Bili Zhan Ge": On the female wall, the rafters are extended outward, with their heads three feet away from the wall. Horizontal wooden strips are used to fix them in place, and pins are installed on the rafters. The Bili are made of thorn and willow branches, measuring two feet in length and five feet in width, hanging from the rafter heads to block arrows and stones. "Bu Man": Double-layered cloth is used to make a curtain, which is hung outside the female wall with flexible poles, seven or eight feet away from the wall. This can reduce the force of flying stones, so arrows and stones cannot reach the wall. "Lian Ting": It is shaped like a rice-harvesting flail, used to beat people climbing the walls. "Cha Gan": It resembles a spear blade but splits into two parts, used to push away enemy ladders and climbers. "Gou Gan": Also resembling a spear blade, it has a curved hook on one side, used to hook enemies and pull them down.

長柄鉤，城上以木為棚，客兵一隊，作長柄鐵鉤，隨安便以為之備。若敵攀女墻踴身，待其身出，眾鉤齊拾，掣入城中，百刀錐斧助之。若敵以木驢攻城，我用鐵蒺藜而入之。其法：以熟鐵為之，闊徑一尺，四條縱橫如蒺藜形，以生鐵汁灌其中央，重五十斤，上安鼻索鎖直下敦訖，以轆轤拗上。若木驢有牛皮並泥，敦著即速放火炬，灌油燒之。

"The Long-Handled Hook": On the city walls, build a scaffold with timber and deploy a squad of guest troops to form long-handled iron hooks, placing them around for emergency use. When the enemy climbs up the parapet and attempts to jump into the city, wait until their bodies are exposed, then have all the hooks simultaneously grab and lift them into the city. After that, use knives, awls, and axes to attack them. If the enemy uses the 'wooden donkey' (a covered wooden framework cart used for mining the city walls), our side should use large iron thorns to attack it. The method is: forge it from seasoned iron, with a diameter of one foot, and have four iron arms cross each other in a thorn-like shape, pour molten iron into the center, weighing fifty jin. Attach a ring at the top and tie a chain to it, then drop it straight down from the city wall to strike the wooden donkey. After striking, use a capstan to pull it back up. If the wooden donkey is covered with cowhide and coated with mud, after striking it, quickly throw torches and pour oil to set it on fire.

鐵菱，狀似小鐵蒺藜，要路撒之。串環，敵若推撞車攻城，我以粗鐵環，並屋乘子為之，用索相連。遇撞頭適到，我速以環串撞頭，於其次便處，將士牽索則撞車翻倒，弓弩齊射，自然敗走。瞇敵，石炭、糠粃，回風〈一作羅〉於城上以瞇敵人目，因以金汁灑之。轉關橋，一梁為橋梁，端著橫栝。拔去栝〈一作橫〉，橋轉關，人馬不得渡，皆傾水中。

"The Iron Thorns": A weapon shaped like a small horn, made of iron thorns, scattered on the main roads to injure horses and soldiers. "Chain Rings": If the enemy pushes a ramming cart against the city, our side uses thick iron rings attached to wooden beams (supporting timber), connected by ropes. When the ramming head is about to hit, the iron rings are quickly fastened around the ramming head. Soldiers pull the ropes together, causing the cart to overturn. At this moment, bows and crossbows fire simultaneously, forcing the enemy to retreat. "Blinding the Enemy": Stone charcoal powder and husks are scattered on the city walls by taking advantage of the swirling wind, blinding the enemy's eyes ("swirling wind" is also written as "net" in some versions). Then, scalding molten metal is poured down. "Turning Bridge": A bridge is made with a single beam as the bridge surface, with a cross pin at the end. When the pin is removed ("hook" is also written as "cross" in some versions), the bridge flips over, blocking passage for soldiers and horses, causing them all to fall into the water.

轉關墻，凡攻城之兵，禦捍矢石，頭戴蠡帽，傾視而不便；衣甲重厚，進退又難；前既不得上城，退則師逼迫，人眾煩鬧。我作轉關女墻，騰出城外，轆轤墜鐵索，索頭安鴟腳，當聚鬧處擲下。撥大木弩，以黃楊、桑、柘為弓，長一丈二尺，中徑七寸，兩梢三寸，絞車張之，大矢一發，聲如雷吼。積木備礨木，徑一尺小，頭六七寸，長五尺，候敵人上城，則擲下礨之。積石備炮石，大小隨身，下從敵人。

"The Turning Wall": When attacking a city, soldiers wear helmet-shaped protective caps made like a gourd to defend against arrows and stones. However, looking sideways is inconvenient because of the caps, and their thick and heavy armor makes movement difficult. They cannot advance onto the city walls, and retreating is blocked by their own troops, so they crowd together in confusion. Our side then constructs a turning wall, flipping it outward and hanging it over the city wall. A pulley is used to lower an iron chain, with an iron claw shaped like a bird's foot at the end. This claw is thrown onto the crowded group of enemies. "Large wooden crossbow": The bow is made from huangyang, sang, and zhe wood, measuring twelve feet in length, with a diameter of seven inches in the middle and three inches at the ends. The bowstring is drawn using a winch, and when the large arrow is fired, it makes a thunderous sound. "Accumulated wooden logs" are prepared as礌wood: they are one foot in diameter, six to seven inches at the smaller end, and five feet long. When enemies climb the walls, these logs are thrown down to crush them. "Accumulated stones" are prepared as cannon stones: they are of various sizes, easily carried, and thrown from the city walls to strike the enemies.

地探，於城西隅穿井，各深二丈，令覆新甕於井上，坐而聽之，城外賊到，有孔城地道，並聞甕中，辯遠近矣。天井，於城內八方穿井，各深二丈，以新甕薄皮鞔口如鼓，令聰耳者於井中枕甕而聽，則去城五百步悉知之。既審其處，我則隨地鑿穴近之，以乾艾一石，燒令煙出，乃用板於穴下封之，而令煙洩。更以韝鼓之，則敵人焦灼矣。

"The 'Ground Exploration' method: dig wells at the western corners of the city, each two zhang deep. Place a new jar upside down on the well's mouth, and have a person sit close to the jar, listening carefully. If enemies approach the city from outside or if someone is digging a tunnel through the city walls, the sounds will be transmitted into the jar, allowing one to determine the distance. 'Heavenly Well': dig a well in each of the eight directions within the city, each two zhang deep. Cover the well mouth with a thin skin stretched tight like a drumhead, and have a person with keen hearing lie on the jar inside the well. This allows the detection of any movement within five hundred steps of the city walls. Once the location of the enemy's tunnel is identified, dig a pit nearby and connect it to the enemy's tunnel. Burn one stone of dry mugwort to produce smoke, then cover the bottom of the pit with wooden boards so the smoke can only flow into the enemy's tunnel. Then use a 'gou' (a leather bellows) to blow air into the tunnel, forcing the smoke into the enemy's passage, causing them to be suffocated by the smoke."

警火，每城四面，夜間設有警火。油囊，盛水，於城上擲安火上，囊敗火滅。救火，用水筒。敵若縱火焚樓堞，以甕竹長一丈，鎪去節，以生薄皮為袋，令貯水二、三石，將筒納於袋內，急縛如唧筒，令將士三五人撮水口，急註之救火。每門常置兩具。無竹，即以木合筒，漆之而用。井水踐筒二十〈一作百〉具助之，門內常以甕貯。

"Alarm fire": The city should have alarm fires set up on all four sides at night. "Water bag": A bag filled with water, which is thrown from the city walls to the place where the fire starts; when the bag breaks, the water flows out to extinguish the fire. "Fire fighting with a water pump": If enemies set fire to the city towers and ramparts, take a long bamboo pole of one zhang in length, remove the middle joints, and make a water bag from thin leather, which can hold two or three stones of water. Insert the bamboo tube into the bag and tightly seal it, making a "water pump" (a type of pressurized water nozzle). Assign three or five soldiers to press the bag mouth together, and quickly spray water to put out the fire. Each city gate should always have two such pumps. If there is no large bamboo, use wooden strips to make a tube, paint it, and then use it. Additionally, provide twenty "well water pumps" to assist in fire fighting ("twenty" is originally written as "two hundred" in some texts). Inside the city gates, large jars filled with water should be kept ready for use.

火炬，用燕尾炬縛葦草為炬，分為兩歧，如燕尾狀，以油蠟灌之，加火縱墜城下，使騎木驢而燒之。松明炬，以松木為之，燒令明，直墜下隨城照之，恐敵人乘暗上城。脂油燭炬，燃脂秉燭於城四隅、要路門下，晨夜不得絕明，用備非常。行轤，熔鐵汁轤，舁行於城上以灑敵。遊火，鐵箱盛火加脂蠟，鏁錘下，燒穴孔中人。毒井，守城之時，城外有井先沈以毒藥。

"Flying Torch": This refers to a swallow-tail torch, made by bundling reed grass into a torch, with the front split into two branches, resembling a swallow's tail. It is soaked in oil and wax, lit, and then dropped from the city walls to specifically burn enemy soldiers riding on wooden carts. "Pine Torch": Made from pine wood, it burns brightly and is dropped straight down along the city walls to illuminate the area, preventing enemies from climbing the walls at night. "Lard Candle Torch": Oil and wax candles are lit at the four corners of the city and at key gateways, and they must remain lit from morning until night to deal with unexpected situations. "Tumbling Ladle": A winch loaded with molten iron is carried by people along the city walls to pour over enemies. "Drifting Fire": A metal box filled with fire and additional oil and wax is lowered with a chain to burn enemies hiding in tunnels and holes. "Poison Well": When defending the city, existing wells outside the city should be pre-treated with poison.

陷馬坑，孔長五尺，闊一丈，深三尺。坑中埋鹿槍、竹戟，沈〈一作坑〉十字相連，狀如鉤鏁，覆以芻草、茆禾，加土種草，令生苗蒙覆其上。軍城、礨壁、要路皆設之。拒馬槍，以木徑二尺，長短隨時，十字鑿孔，縱橫安栝，長一丈，銳其端，可用塞城門，要路。木柵，為敵所逼，不及築城礨，或因山河險隘，多石少土，不任板築，則建立木為棚，方圓高下隨時。深埋木棍，彌縫其疏闊。內重柱為閣道，外重柱長出女墻，皆入泥七八寸。又立閣道，內柱上布板為棧，立闌干，行於柵上懸門。擁墻、濠塹、拒馬，一如守城法。

"The 'Trap Pit': The pit is five feet long, ten feet wide, and three feet deep. Inside the pit, deer horns and bamboo spears are placed, arranged in a cross pattern so that they connect in a series of interlocking hooks. A layer of dry grass and straw is then placed on top, followed by soil to grow grass, which covers the pit's surface. These pits should be set up near military camps, fortifications, and key roads. 'Obstacle Pikes': Use wooden poles with a diameter of two feet, with length determined as needed. Drill cross-shaped holes and insert one-meter-long wooden stakes, sharpening the ends to block city gates and important roads. 'Wooden Fences': When enemies approach quickly and there is no time to build fortifications, or when in mountainous or riverine areas with many stones and little soil, making rammed earth walls is not possible, then wooden poles are erected to form a fence. The size and height are determined as needed. The wooden posts should be deeply buried, and any gaps should be filled tightly. Inside, a row of poles is set up to form a passageway, while another row of poles is built higher than the parapet, with their bases buried about seven or eight inches into the ground. Then a passageway is constructed on top of these poles, covered with planks and fitted with railings, allowing people to move along the fence. Suspended doors can also be installed. As for other defenses such as walls, ditches, and obstacle pikes, they should all be constructed according to standard fortification methods."

轒轀車，四輪車，上以繩為脊，犀革蒙之，下可藏十人。填隍推之，直抵城下，可以攻掘，金、木、水、火、石所〈一作俱〉不能敗。

"The 'Hunwen chariot' is a four-wheeled vehicle with a roof made of ropes woven into a ridge shape, covered externally with rhinoceros hide, and capable of hiding ten people underneath. First, fill in the moat, then push the chariot forward until it reaches the foot of the city wall, with people working underneath to dig through the wall. Gold, wood, water, fire, and stone cannot damage it."

飛雲梯，一大木為床，床下置六輪，上立雙牙，牙有栝，梯長一丈二尺，有四桄，桄相去三尺，勢微曲遞相栝。飛於雲間，以窺城中。其上城，首冠雙轆轤，枕城而上。

"The Flying Cloud Ladder": Use a large wooden frame as the base, with six wheels attached underneath. Two upright posts are mounted on the frame, with pins fitted on top of them. The ladder is twelve chi long, with four crossbars evenly spaced three chi apart. The ladder itself has a slight curve, and is extended section by section with pins. When raised high, it appears to fly among the clouds, allowing one to look into the city. When used to climb a city wall, a pair of winches are attached to the top of the ladder, which are then leaned against the wall to facilitate climbing.

炮車，以大木為床，床下安四輪，上建雙陛，陛間橫栝，中立獨竿，竿首如桔橰狀。其竿高下、長短、大小，以城為準。竿首以窠盛石，大小多少，隨竿力所制。人挽其端而投之。其車推輪，逐便而用之，亦可埋腳著地而用之。其旋風四腳，亦隨事而用。

"The 'Paoche' [trebuchet], refers to a type of catapult: it is constructed with a large wooden frame, with four wheels underneath. Two vertical pillars are erected on the frame, with a horizontal pin connecting them. In the middle, a single pole is erected, with the top of the pole shaped like a water-lifting lever. The height, length, and thickness of the pole are determined according to the height of the city wall it is intended to attack. At the top of the pole, a leather pouch is attached to hold the stones. The size and number of stones depend on the pole's ability to bear weight. People pull the other end of the pole forcefully to launch the stones. This vehicle can be moved on wheels to any location for easy use; alternatively, the frame can be fixed in place by burying its legs into the ground. As for the 'Xuanfengpao' [spinning wind cannon], which has a four-legged frame, it is also used according to the situation."

車弩，為軸轉車，車上定十四石弩弓，以鐵鉤繩連軸，車行軸轉，引弩弓持滿弦掛牙上。弩為七衢，中衢大箭一，鏃刃長七寸廣五寸，簳長三尺圍五寸，以鐵葉為羽。左、右各三箭，次小於中箭。其牙一發，諸箭皆起，及七百步，所中城壘罔〈一作無〉不崩潰ソ櫓以便顛墜。

"The 'chariot crossbow'": A vehicle is constructed that can rotate its axle, with a crossbow of fourteen stone strength fixed on it. The crossbow is connected to the axle via an iron hook and rope. When the vehicle is pushed forward, it turns the axle, which draws back the crossbow string and hooks it onto the crossbow hook. The crossbow has seven arrow slots: one in the center for a large arrow, with the arrowhead being seven inches long and five inches wide, the shaft three feet long and five inches in circumference, and iron plates used as fletching. On either side, there are three arrows each, each successively smaller than the central arrow. When the crossbow hook is released, all arrows fly out together, with a range of up to seven hundred paces. The walls of the city that are hit will surely collapse (the character '罔' in some editions is '无'), and even the watchtowers on the city walls will also collapse.

尖頭木驢，以木為脊，長一丈，徑一尺五寸，下安六腳。下闊而上尖，頭高七尺，內可容六人，用濕牛皮蒙之。蔽人其下，共舁至敵城下，木、石、鐵、火皆不能敗，用攻其城。

"The sharp-headed wooden donkey": made of wood with a length of ten chi and a diameter of one foot five cun, with six legs at the bottom; it is wide at the bottom and tapers to a point at the top, with the front seven chi high. Inside it can accommodate six people, and the outside is covered with wet cowhide. People hide underneath it for cover and carry it together to the foot of the enemy's city walls. It cannot be damaged by wood, stone, iron, or fire, and it is used to protect those who dig through the city walls.

土山，於城外起土為山，乘城而上。地道，鑿地為道，行於城下，因以攻城。往往建柱，積薪於柱，閑而焚之，柱折而城崩。

"Earth Mountain": Building a hill of earth outside the city to occupy a high position and attack the city from above. "Underground Passage": Digging tunnels underground to reach beneath the city walls, thus attacking the city. When digging to the base of the city wall, they often first set up wooden pillars to support the base, then pile firewood beside the pillars and set fire to it at intervals. When the pillars break, the city wall collapses.

板屋，以八輪車，上樹高竿，竿下安轆轤，以繩挽板屋，上竿首以窺城中。板屋方四尺，高五尺，有十二孔，四面列布。車可進退，圍城而行，於營中遠望，謂之巢車，言如鳥巢也。木幔，以板為幔，立桔橰於四輪車上，懸帳逼城其間，使し卒蔽之，蟻附而上，矢石亦不能及。

"Board House": Using an eight-wheeled cart, a tall pole is erected on top, with a winch attached below. A board house is hoisted up to the top of the pole by a rope, and people inside can look into the city. The board house is four feet square and five feet high, with twelve holes opened in the four walls. The cart can move forward or backward, circling the city, or can be used for distant observation within the camp. This is called "Nest Cart," because it is like a bird's nest suspended on a pole. "Wooden Canopy": Made of wooden boards, the canopy is set up on a four-wheeled cart, with a lever system similar to a well-pulley used to lift the canopy close to the city walls. Soldiers hide behind the canopy, climbing up the walls like ants, and are not harmed by arrows or stones.

發火箭，以小瓢盛油灌矢端，射城樓櫓板木上，瓢敗油散，因以火箭射油散處，火立燃，復以油瓢續之，則樓櫓盡焚。

"Launching rockets": Use a small ladle filled with oil tied to the arrowhead, shoot it onto the wooden planks of the city tower or the gallery, and when the ladle breaks, the oil splashes out; then shoot rockets towards the splashed oil, and the fire immediately starts, and then continue shooting oil ladles to keep the oil flowing, and the city tower and gallery will be completely burned down.

雀杏，磨杏子中空，以艾實之，繫雀足上，加火，於薄莫群飛入城壘中棲宿，其積聚廬舍須臾火發。蜀鐵釒瞿鋤，蜀釒瞿短柄，著鋼鐵鏨，以鋤其城。

"The Què Xìng" method involves hollowing out a apricot kernel, filling it with dried mugwort, and attaching it to a sparrow's foot. Then, it is lit on fire and released at dusk. When the sparrows fly into the enemy's camp to roost, the enemy's stored supplies and buildings catch fire instantly. "Shǔ Tī Zhǔ Chú" refers to a type of hoe from Shǔ region, with a short handle and a steel-bladed head, used for digging through city walls.

將軍炮，置四柱，長短為之，其下四面著橫栝，半之則前及左右著栝後，其下著其頂上，左右亦頂轉輪致卒其竿，隨其架所宜為之。其ㄌ索之類，隨其炮大小增減。竿稍懸其繩置窠，中盛炮，其架編全竹為衣，以禦敵矢石。

"The General's Cannon": Set up four pillars, whose lengths are determined by the need. At the base of each pillar, attach horizontal wooden bars on all four sides, half of them facing the front and sides, and the other half facing the back. At the junction between the lower and upper parts, attach rotating wheels at the top ends to support the launching rods. Everything is made according to the actual structure of the frame. The ropes used, along with other equipment, are adjusted according to the size of the cannon. The end of the launching rod is tied with a rope and attached to a "ke" (a leather pouch), which holds stone projectiles. A whole bamboo frame is woven outside the cannon frame to serve as a protective garment, shielding against enemy arrows and stones.

狗蹲炮，前置兩長柱，中著橫竿，如前炮狀，與衣亦然。旋風炮，左右著二方木，亦如之鑿一孔通貫下柱，左右前後皆可運轉，埋之於地，其頂轉輪著竿如前狀。此炮不用衣。

"The Dog Crouching Cannon": It consists of two long pillars placed in front, with a horizontal pole spanning between them, and its structure is the same as the previous type of cannon, using the same protective cover. "Whirlwind Cannon": Two square wooden beams are mounted on both sides, with a hole drilled through the wood to connect to the vertical pillars below, allowing rotation in all directions. The base of the pillars is buried in the ground, and a rotating wheel is mounted on top to support the throwing pole, which is the same as described earlier. This type of cannon does not use a protective cover.

令少睡者枕空葫蘆臥，有人行，四十里外，東西南北皆知之。

Select soldiers who have light sleep and are easily startled, and have them sleep with an empty gourd placed on the ground beneath their heads. The hollow cavity of the gourd can gather and amplify vibrations transmitted from the ground. As long as there are people or horses moving, sounds from as far as forty li away can be heard, and it is also possible to determine from which direction—east, west, south, or north—the sound is coming. This is the method of "earth listening" used by the military to detect enemy movements.