Stirrup crossbow, French, 14th century
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A crossbow is a weapon consisting of a bow mounted on a stock that shoots projectiles, often called bolts. It is created in the Mediterranean and in China separately (since the designs from the areas are so different historians believe they were invented without connection to each other). A mechanism in the stock holds the bow in its fully-drawn position until it is shot by releasing a trigger. Crossbows played a significant role in the warfare of North Africa, Europe and Asia. Crossbows are used today primarily for target shooting and hunting.
The bow (called the "prod" or "lath" on a crossbow) of early crossbows were made of a single piece of wood, usually ash or yew. Composite bows are made from layers of different material—often wood, horn and sinew—glued together and bound with animal tendon. These composite bows, made of several layers, are much stronger and more efficient in releasing energy than simple wooden bows. As steel became more widely available in Europe around the 14th century, steel prods came into use.
The crossbow prod is very short compared to ordinary bows, resulting in a short draw length. This leads to a higher draw weight in order to store the same amount of energy. Furthermore the thick prods are a bit less efficient at releasing energy, but more energy can be stored by a crossbow. Traditionally the prod was often lashed to the stock with rope, whipcord, or other strong cording. This cording is called the bridle. The strings for a crossbow are typically made of strong fibers that would not tend to fray. Whipcord was very common; however linen, hemp, and sinew were used as well. In wet conditions, twisted mulberry root was occasionally used.
The problem when handling crossbows was the comparably short draw length and the great amount of force needed to draw them. Some light crossbows could be drawn by hand, but for others the help of mechanical devices was needed. Some crossbows had prods of up to at least 800 pounds of draw, if not more. Draw-weights of 500 pounds were common. The simplest version of mechanical cocking device was a hook attached to a belt, drawing the bow by straightening the legs. Other devices were hinged levers which either pulled or pushed the string into place, cranked rack-and-pinion devices called 'cranequins' and multiple cord-and-pulley cranked devices called windlasses.
Crossbows exist in different variants, one way to classify them is the acceleration system, another the size and energy, degree of automation or projectiles.
The simplest acceleration system is a straight or bent prod and it is probably the earliest version of a crossbow.
A recurve crossbow is a bow that has tips curving away from the archer. The recurve bow's bent limbs have a longer draw length than an equivalent straight-limbed bow, giving a more acceleration to the projectile and less hand shock. Recurved limbs also put greater strain on the materials used to make the bow, and they may make more noise with the shot.
Multiple bow systems (for example a Chu-ko-nu) have a special system of pulling the sinew via several bows (which can be recurve bows). The workings can be compared to a modern compound bow system. The weapon uses several different bows instead of one bow with a tackle system to achieve a higher acceleration of the sinew via the multiplication with each bow's pulling effect.
A compound crossbow is a modern crossbow and similar to a compound bow, The limbs are usually much stiffer than those of a recurve crossbow. This limb stiffness makes the compound bow more energy efficient than other bows, but the limbs are too stiff to be drawn comfortably with a string attached directly to them. The compound bow has the string attached to the pulleys, one or both of which has one or more cables attached to the opposite limb. When the string is drawn back, the string causes the pulleys to turn. This causes the pulleys to pull the cables, which in turn causes the limbs to bend and thus store energy. The use of this levering system gives the compound bow a characteristic draw-force curve which rises to a peak weight and then "lets off" to a lower holding weight.
In size the smallest are pistol crossbows. Others are simple long stocks with the crossbow mounted on them. These could be shot from under the arm. The next step in development was rifle shaped stocks that allowed better aiming. The arbalest was a heavy crossbow which required special systems for pulling the sinew via windlasses. For siege warfare the size of crossbows was further increased to hurl large projectiles such as rocks at fortifications. The required crossbows needed a massive base frame and powerful windlass devices. Such devices include the oxybeles. The ballista has torsion springs replacing the elastic prod of the oxybeles, but later also developed into smaller versions. "Ballista" is still the root word for crossbow in Romance languages such as Italian (balestra).
The repeating crossbow automated the separate actions of stringing the bow, placing the projectile and shooting. This way the task can be accomplished with a simple one-handed movement, while keeping the weapon stationary. As a result, it is possible to shoot at a faster rate compared to unmodified version. The Chinese repeating crossbow, Chu Ko Nu, is a small handheld crossbow that accomplishes the task with a magazine containing a number of bolts on top. The mechanism is worked by moving a rectangular lever forward and backward.
A bullet crossbow is a type of handheld crossbow which rather than arrows or bolts shoots spherical projectiles made of stone, clay or lead. There are two variants, one has a double string with a pocket for the projectile; the other has a barrel with a slot for the string.
The arrow-like projectiles of a crossbow are called bolts. These are much shorter than arrows, but can be several times heavier. There is an optimum weight for bolts to achieve maximum kinetic energy, which varies depending on the strength and characteristics of the crossbow. In ancient times the bolts of a strong crossbow were usually several times heavier than arrows. Modern bolts are stamped with a proof mark to ensure their consistent weight. Bolts typically have three fletches, commonly seen on arrows. Crossbow bolts can be fitted with a variety of heads, some with sickle-shaped heads to cut rope or rigging; but the most common today is a four-sided point called a quarrel. A highly specialized type of bolt can be employed to collect blubber biopsy samples used in biology research.
Crossbows could be adapted to also lead bullets or shoot stones, in which case they are called stone-bows. Primarily used for hunting wildfowl, these usually have a double string with a pouch between the strings to hold the projectile.
The ancient crossbow often included a metal grid serving as iron sights. Modern crossbow sights often use similar technology to modern firearm sights such red dot sights and telescopic sights. Many crossbow scopes feature multiple crosshairs to compensate for the significant effects of gravity over different ranges.
Quivers can be mounted to hold ammunition. These are often made from plastic and usually hold the bolts in fixed positions along the structure. A popular detachable design consists of a main arm that is attached to the weapon, a plate on one end that secures four or more individual bolts at a point on their shafts and at the other end a cover that secures their heads. This kind of quiver is attached under the front of the crossbow, parallel to the string and is designed to be quickly detached and reattached. Other designs hold bolts underneath the crossbow parallel to the stock, sometimes on either side of the crossbow.
A major cause of the sound of firing a crossbow is vibration of various components. Crossbow silencers are multiple components placed on high vibration parts such as the string and limbs to dampen vibration and suppress the sound of loosing the arrow.
The earliest Chinese document mentioning a crossbow is in scripts from the 5th century BC attributed to the followers of Mozi. This source refers the use of a giant crossbow catapult to the 6th to 5th century BC, corresponding to the late Spring and Autumn Period. Sun Tzu's influential book The Art of War (first appearance dated in between 500 BC to 300 BC) refers in chapter V to the traits and in XII to the use of crossbows. One of the earliest reliable records of this weapon in warfare is from an ambush, the Battle of Ma-Ling in 341 BC. By the 200s BC, the crossbow (nǔ, 弩) was well developed and quite widely used in China. Several remains of them have been found among the soldiers of the Terracotta Army in the tomb of Emperor Qin Shi Huang (260-210 BC). The earliest crossbow bolts found in China come from a 5th century BC State of Chu grave in Hubei, while the oldest crossbow stocks with bronze triggers were found in a 4th century BC grave in Hunan. While discussing advantages and disadvantages of both the nomadic Xiongnu and Han armies in a memorandum to the throne in 169 BC, the official Chao Cuo (d. 154 BC) deemed the crossbow and repeating crossbow of Han armies superior to the Xiongnu bow, even though the latter were trained to shoot behind themselves while riding.
The earliest date for the crossbow in the European world is from the 5th century BC, from the Greek world. The historian Diodorus Siculus (fl. 1st century BC), described the invention of a mechanical arrow firing catapult (katapeltikon) by a Greek task force in 399 BC. The weapon was soon after employed against Motya (397 BC), a key Carthaginian stronghold in Sicily. Diodorus is assumed to have drawn his description from the highly rated history of Philistus, a contemporary of the events then. The date of the introduction of crossbows, however, can be dated further back: According to the inventor Hero of Alexandria (fl. 1st c. AD), who referred to the now lost works of the 3rd century BC engineer Ctesibius, this weapon was inspired by an earlier hand-held crossbow, called the gastraphetes (belly shooter), which could store more energy than the Greek bows. A detailed description of the gastraphetes, along with a drawing, is found in Heron's technical treatise Belopoeica. A third Greek author, Biton (fl. 2nd c. BC), whose reliability has been positively reevaluated by recent scholarship, described two advanced forms of the gastraphetes, which he credits to Zopyros, an engineer from southern Italy. Zopyrus has been plausibly equated with a Pythagorean of that name who seems to have flourished in the late 5th century BC. He probably designed his bow-machines on the occasion of the sieges of Cumae and Milet between 421 BC and 401 BC. The bows of these machines already featured a winched pull back system and could apparently throw two missile at once.
Linguistic evidence makes it the more probable hypothesis that the crossbow may have originated among the cultures neighboring ancient China. It was used as weapon and toy, but mainly in the form of unattended traps.
There are no attestations through pictures or archaeological finds, but the description by Heron is detailed enough to have allowed modern reconstructions to be made. Its application in sieges featured more and more powerful projectiles, leading first to the larger oxybeles and then to technical improvements with the ballista. The ballista is a torsion weapon, not being a tension weapon and for this reason it isn't considered a crossbow.
The use of crossbows in European warfare dates back to Roman times and is again evident from the battle of Hastings until about 1500 AD. They almost completely superseded hand bows in many European armies in the twelfth century for a number of reasons. Although a longbow could achieve comparable accuracy and faster shooting rate than an average crossbow, crossbows could release more kinetic energy and be used effectively after a week of training, while a comparable single-shot skill with a longbow could take years of practice.
In the armies of Europe, mounted and unmounted crossbowmen, often mixed with javeliners and archers, occupied a central position in battle formations. Usually they engaged the enemy in offensive skirmishes before an assault of mounted knights. Crossbowmen were also valuable in counterattacks to protect their infantry. The rank of commanding officer of the crossbowmen corps was one of the highest positions in any army of this time. Along with polearm weapons made from farming equipment, the crossbow was also a weapon of choice for insurgent peasants such as the Taborites.
Mounted knights armed with lances proved ineffective against formations of pikemen combined with crossbowmen whose weapons could penetrate most knights' armor. The invention of pushlever and ratchet drawing mechanisms enabled the use of crossbows on horseback, leading to the development of new cavalry tactics. Knights and mercenaries deployed in triangular formations, with the most heavily armored knights at the front. Some of these riders would carry small, powerful all-metal crossbows of their own. Crossbows were eventually replaced in warfare by gunpowder weapons, although early guns had slower rates of fire and much worse accuracy than contemporary crossbows. Later, similar competing tactics would feature harquebusiers or musketeers in formation with pikemen, pitted against cavalry firing pistols or carbines.
The Saracens called the crossbow qaws Ferengi, or "Frankish bow", as the Crusaders used the crossbow against the Arab and Turkoman horsemen with remarkable success. The adapted crossbow was used by the Islamic armies in defence of their castles. Later footstrapped version become very popular among the Muslim armies in Spain. During the Crusades, Europeans were exposed to Saracen composite bows, made from layers of different material—often wood, horn and sinew—glued together and bound with animal tendon. These composite bows could be much more powerful than wooden bows, and were adopted for crossbow prods across Europe.
In Western Africa and Central Africa, crossbows serve as a scout weapon and for hunting, with enslaved Africans bringing the technology to America. In the American south, the crossbow was used for hunting when firearms or gunpowder were unavailable because of economic hardships or isolation. Light hunting crossbows were traditionally used by the Inuit in Northern America.
In many regions of the world they are still used for hunting, such as parts of North America, Asia, Australia, and Africa. Other uses, which involve special projectiles, are in whale research to take blubber biopsy samples without harming the whales.
A few modern military special forces units such as the Indian Navy's Marine Commando Force were once equipped with crossbows supplied with cyanide-tipped arrows, as an alternative to suppressed handguns.
With a crossbow, archers could release a draw force far in excess of what they could have handled with a bow. Moreover, crossbows could be kept cocked and ready to shoot for some time with little effort, allowing crossbowmen to aim better. The disadvantage is the greater weight and clumsiness compared to a bow, as well as the slower rate of fire and the lower efficiency of the acceleration system.
Crossbows have a much smaller draw length than bows. This means that for the same energy to be imparted to the arrow (or bolt) the crossbow has to have a much higher draw weight.
Today the crossbow often has a complicated legal status due to the possibility of lethal use and its similarities with both firearms and archery weapons.