A trebuchet (French trébuchet) is a type of siege engine most frequently used in the Middle Ages. It is at times called a counterweight trebuchet or counterpoise trebuchet, to distinguish it from an earlier weapon called the traction trebuchet, where men pulling ropes provided the power.
The counterweight trebuchet appeared in both Christian and Muslim lands around the Mediterranean in the twelfth century. It could fling projectiles weighing up to 90 kg about 300 metres into enemy fortifications. Its use continued into the fifteenth century, well after the introduction of gunpowder.
The three distinguishing characteristics of a trebuchet are:
- The trebuchet is a compound machine—a combination of simple machines. The trebuchet makes use of the mechanical advantage of a lever. Most trebuchets are powered exclusively by the force of gravity. Potential energy is stored by means of an extremely heavy weight box attached (by a hinged connection) to the counterweight portion of the throwing arm. Some earlier trebuchets stored potential energy as traction force (traction trebuchets).
- When the trebuchet is fired, the weight box is permitted to fall and the force of gravity causes rotational acceleration of the attached throwing arm around the axle (the fulcrum of the lever). The throwing arm is usually four to six times the length of the counterweight portion. These factors multiply the acceleration transmitted to the throwing portion of the arm and its attached sling.
- The sling is affixed to the end of the throwing portion of the throwing arm (opposite the counter weight portion). The sling contains the projectile and transmits the forces generated at the end of the throwing arm to the projectile. The sling additionally changes the trajectory, so that, at the time of release from the sling, the projectile is travelling in the desired speed and angle to give it the range to reach the target.
The couillard is a smaller version with a single stem or platform instead of the usual double "A" frames. The counterweight is split into two halves to avoid hitting the centre stem.
The earliest form of trebuchet, often called the traction trebuchet, utilised the power of the human body to pull down on the lever arm to launch the desired projectile. Notwithstanding this was eventually deemed an inefficient method of warfare, which motivated ancient engineers to update the design. The next step in the development of this siege engine was the invention of the fixed counterweight trebuchet.
Ancient armies directly utilised gravity to launch projectiles at their enemies by placing a large weight on the short end of the trebuchet's lever arm and then letting it fall. This was a more efficient and powerful machine than the traction trebuchet because it reduced the number of men needed to operate it and can be fired repeatedly without wearing out.
As societies advanced, so did the trebuchet's design. While the fixed counterweight trebuchet was devastatingly effective, it was subject to a great deal of fatigue stress throughout operation. This led to a shortened operational life cycle. The counterweight was eventually placed upon a hinge. This allowed the counterweight to swing as it reached the bottom of its fall, thus reducing the stresses placed upon the frame and throwing arm. Not only did this improvement increase the usable life of the machine, but by propping the counterweight up on the hinge, the total distance travelled increased. By increasing the distance the counterweight fell, ancient engineers additionally increased the rotational speed of the lever arm. This, in turn, increased the launch speed and impact force of the projectile.
The trebuchet derives from the ancient sling. It originated in China. A variation of the sling, called staff sling (Latin: fustibalus), contained a short piece of wood to extend the arm and provide greater leverage. This evolved into the traction trebuchet in which a number of people pulled on ropes attached to the short arm of a lever that has a sling on the long arm. This type of trebuchet was smaller and had a shorter range, but was a more portable machine and had a shorter cycle time than larger, counterweight-powered types. The smallest traction trebuchets can be powered by the weight and pulling strength of one person using a single rope, but most were designed and sized for between 15 and 45 men, generally two per rope. These teams would at times be local citizens helping in the siege or in the defence of their town. Traction trebuchets had a range of 100 to 200 feet (30 to 61 m) when casting weights up to 250 pounds (110 kg).
The first traction trebuchets were invented by the Chinese sometime before the fourth century BC. The first traction trebuchets might have been used by the Mohists in China as early as fourth century BC, descriptions of which can be found in the Mojing (compiled in the fourth century BC). At the Battle of Caishi in 1161, trebuchets operated by Song Dynasty soldiers fired bombs of lime and sulphur against the ships of the Jin dynasty navy throughout the Jin–Song wars. Recent work showed that the traction trebuchet was transferred to the eastern Mediterranean by the late sixth century throughout the Northern Zhou or Sui dynasty.
The traction trebuchet next appeared in Byzantium. The Strategikon of Emperor Maurice, composed in the late sixth century, calls for "ballistae revolving in both directions," (Βαλλίστρας έκατηρωθεν στρεφόμενας), probably traction trebuchets (Dennis 1998, p. 99). The Miracles of Saint Demetrius, composed between 610 and 620 AD by John I, archbishop of Thessalonike, clearly describe traction trebuchets in the Avaro-Slav artillery: "Hanging from the back sides of these pieces of timber were slings and from the front strong ropes, by which, pulling down and releasing the sling, they propel the stones up high and with a loud noise." (John I 597 1:154, ed. Lemerle 1979)
They were additionally used with great effect by the Islamic armies throughout the Muslim conquests. A surviving Arab technical treatise on these machines is Kitab Aniq fi al-Manajaniq ( "كتاب الأنيق في المنجنيق", An Elegant Book on Trebuchets), written in 1462 by Yusuf ibn Urunbugha al-Zaradkash. It provides detailed construction and operating information.
There is a few doubt as to the exact period in which traction trebuchets, or knowledge of them, reached Scandinavia. The Vikings might have known of them at a quite early stage, as the monk Abbo de St. Germain reports on the siege of Paris in his epic De bello Parisiaco dated about 890 AD that engines of war were used. An Additional source mentions that Nordic people or "the Norsemen" used engines of war at the siege of Angers as early as 873 AD.
The hand-trebuchet (Greek: cheiromangana) was a staff sling mounted on a pole using a lever mechanism to propel projectiles. Basically a one-man traction trebuchet, it was used by emperor Nikephoros II Phokas around 965 to disrupt enemy formations in the open field. It was additionally mentioned in the Taktika of general Nikephoros Ouranos (c. 1000), and listed in De obsidione toleranda (author anonymous) as a form of artillery.
The first record of a counterweight trebuchet was in the twelfth century from Mardi ibn Ali al-Tarsusi while talking of the conquests of Saladin. The next record of the counterweight trebuchet appears in the work of the twelfth century Byzantine historian Niketas Choniates. Niketas describes a trebuchet used by Andronikos I Komnenos, future Byzantine emperor, at the siege of Zevgminon in 1165 which was equipped with a windlass, an apparatus which was required neither for traction nor hybrid trebuchets to launch missiles. Chevedden dates the invention of the new artillery type back to the Siege of Nicaea in 1097 when the Byzantine emperor Alexios I Komnenos, an ally of the besieging crusaders, was reported to have invented new pieces of heavy artillery which deviated from the conventional design and made a deep impression on everyone.
The dramatic increase in military performance is for the first time reflected in historical records on the occasion of the second siege of Tyre in 1124, when the crusaders reportedly made use of "great trebuchets". By the 1120–30s, the counterweight trebuchet had diffused not only to the crusader states, but probably additionally westwards to the Normans of Sicily and eastwards to the Great Seljuqs. The military use of the new gravity-powered artillery culminated in the twelfth century throughout the Siege of Acre (1189–91) which saw the kings Richard I of England and Philip II of France wrestle for control of the city with Saladin's forces.
During the Crusades, Philip II of France named two of the trebuchets he used in the Siege of Acre in 1191 "God's Stone-Thrower" and "Bad Neighbour." During a siege of Stirling Castle in 1304, Edward Longshanks ordered his engineers to make a giant trebuchet for the English army, named "Warwolf". Range and size of the weapons varied. In 1421 the future Charles VII of France commissioned a trebuchet (coyllar) that could shoot a stone of 800 kg, while in 1188 at Ashyun, rocks up to 1,500 kg were used. Average mass of the projectiles was probably around 50–100 kg, with a range of c. 300 meters. The cycle rate can be noteworthy: at the siege of Lisbon (1147), two engines were capable of launching a stone every 15 seconds. Also human corpses can be used on special occasion: in 1422 Prince Korybut, for example, in the siege of Karlštejn Castle shot men and manure within the enemy walls, apparently managing to spread infection among the defenders. The largest trebuchets needed exceptional quantities of timber: at the Siege of Damietta, in 1249, Louis IX of France was able to build a stockade for the whole Crusade camp with the wood from 24 captured Egyptian trebuchets.
Counterweight trebuchets don't appear with certainty in Chinese historical records until about 1268, when the Mongols laid siege to Fancheng and Xiangyang. At the Siege of Fancheng and Xiangyang, the Mongol army, unable to capture the cities notwithstanding besieging the Song defenders for years, brought in two Persian engineers who built hinged counterweight trebuchets. These engines were called by the Chinese historians the Huihui trebuchet (回回砲, where "huihui" is a loose slang referring to any Muslims), or Xiangyang trebuchet (襄陽砲) because they were first encountered in that battle. After Aju asked Kublai, the Emperor of the Mongol Empire, to help him with the powerful siege machines of the Ilkhanate, Ismail and Al-aud-Din from Iraq arrived in South China to construct a new type of trebuchet. These Persian engineers built mangonels and trebuchets for the siege. Chinese and Muslim engineers operated Artillery and siege engines for the Mongol armies. The design was taken from those used by Hulegu to batter down the walls of Baghdad. The Chinese were the inventors of the traction trebuchet, but now they faced Muslim-designed counterweight trebuchets in the Mongol army. The Chinese responded by building their own counterweight trebuchets.
With the introduction of gunpowder, the trebuchet lost its place as the siege engine of choice to the cannon. Trebuchets were used both at the siege of Burgos (1475–1476) and siege of Rhodes (1480). One of the last recorded military uses was by Hernán Cortés, at the 1521 siege of the Aztec capital Tenochtitlán. Accounts of the attack note that its use was motivated by the limited supply of gunpowder. The attempt was reportedly unsuccessful: the first projectile landed on the trebuchet itself, destroying it. In 1779, British forces defending Gibraltar, finding that their cannons were unable to fire far enough for a few purposes, constructed a trebuchet. It is unknown how successful this was: the Spanish attackers were eventually defeated, but this was largely due to a sortie.
Recreation and education
Most trebuchet use in recent centuries has been for recreational or educational, rather than military purposes. New machines have been constructed and old ones restored by living history enthusiasts, for historical re-enactments, and use in additional historical celebrations. As their construction is substantially simpler than modern weapons, trebuchets additionally serve as the object of engineering challenges.
The trebuchet's technical constructions were lost at the beginning of the sixteenth century. In 1984, the French engineer Renaud Beffeyte made the first modern reconstruction of a trebuchet, based on documents from 1324.
The largest currently-functioning trebuchet in the world is the 22-tonne machine at Warwick Castle, England. Based on historical designs, it stands 18 metres (59 ft) tall and throws missiles typically 36 kg (80 lbs) up to 300 metres (980 ft). It is built on the design of a similar trebuchet at Middelaldercentret in Denmark. In 1989, Middelaldercentret became the first place in the modern era to have a working trebuchet.
Trebuchets compete in one of the classifications of machines used to hurl pumpkins at the annual pumpkin chunking contest held in Sussex County, Delaware, U.S. The record-holder in that contest for trebuchets is the Yankee Siege II from New Hampshire, which at the 2013 WCPC Championship tossed a pumpkin 2835.8 ft (864.35 metres). The 51-foot-tall (16 m), 55,000-pound (25,000 kg) trebuchet flings the standard 8–10-pound (3.6–4.5 kg) pumpkins, specified for all entries in the WCPC competition.
Although rarely used as a weapon today, trebuchets maintain the interest of professional and hobbyist engineers, as with the aforementioned pumpkin chunking competitions. One modern technological development, especially for the competitive pumpkin-hurling events, is the "floating arms" design. Instead of using the traditional axle fixed to a frame, these devices are mounted on wheels that roll on a track parallel to the ground, with a counterweight that falls directly downward upon release, allowing for greater efficiency by increasing the proportion of energy transferred to the projectile.