Crossbow

A crossbow is a weapon consisting of a bow mounted on a stock that shoots projectiles, often called bolts or quarrels. The medieval crossbow was called by many names, most of which derived from the word ballista, a torsion engine resembling a crossbow in appearance. Historically, crossbows played a significant role in the warfare of East Asia, Europe, and the Mediterranean. Today, they are used primarily for target shooting and hunting.

Overview


A crossbow is a bow mounted on a stick (called a tiller or stock) with a mechanism in it which holds the drawn bow string. The earliest designs featured a slot in the stock, down into which the cocked string was placed. To fire this design, a vertical rod is thrust up through a hole in the bottom of the notch, forcing the string out. This rod is usually attached perpendicular to a rear-facing firing lever called a trigger or 'tickler'. A later design implemented a rolling cylindrical pawl called a 'nut' to retain the cocked string. This nut has a perpendicular center slot for the bolt, and an intersecting axial slot for the string, along with a lower face or slot against which the internal trigger sits. They often also have some form of strengthening internal 'sear' or trigger face, usually of metal. These 'roller nuts' were either free-floating in their close-fitting hole across the stock, tied in with a binding of sinew or other strong cording, or mounted on a metal axle or pins. Removable or integral plates of wood, ivory or metal on the sides of the stock kept the nut in place laterally. Nuts were made of antler, bone, ivory or metal (usually brass). A trigger system, (usually made of iron or steel from medieval times onwards), was used to retain the force of the cocked string in the nut and then release the nut to spin and the string to shoot the bolt. Sophisticated bronze triggers with safety notches are known to have been used on crossbows from ancient China. Complicated iron triggers that could be released with little strength are known in Europe from the early 1400s. As a result crossbows could be kept cocked and ready to shoot for some time with little effort, allowing crossbowmen to aim better.

The bow (called the "prod" or "lath" on a crossbow) of early crossbows was made of a single piece of wood, usually ash or yew. Composite bows are made from layers of different material&mdash;often wood, horn and sinew&mdash;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.

Crossbows have a shorter draw length than bows, resulting in the need of a greater amount of draw force in order to store the same amount of energy. Very light crossbows can be drawn by hand, but heavier types need the help of mechanical devices. The simplest version of mechanical cocking device is a hook attached to a belt, drawing the bow by straightening the legs. Other devices are 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.

Variants


Crossbows exist in different variants. One way to classify them is the acceleration system, while another is 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 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 is 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. Other types of compound bows use either (one or both) cam shaped or excentrically mounted pulleys in order to provide a "let off", such that the archer is not holding against the maximum draw weight of the bow while trying to aim. But in a crossbow the string is held back mechanically, so there is no advantage in providing a let off. Therefore, compound crossbows generally use only pulleys that are both round and concentrically mounted, in order to capture the maximum available energy from the relatively short draw length.

The smallest crossbows 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 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. The weapon was mainly used as a weapon against lightly armored soldiers, since it fired small bolts that were often dipped in poison.

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.

Projectiles


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, but most could pass through common chain mail. 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 can also be adapted to shoot lead bullets or 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.

Accessories


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, laser 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.

Ancient China


Bronze crossbow bolts dating as early as mid 5th century BC were found at a State of Chu burial site in Yutaishan, Hubei. The earliest handheld crossbow stocks with bronze trigger, dating from the 6th century BC, comes from Tomb 3 and 12 found at Qufu, Shandong, capital of the State of Lu. Other early finds of crossbows were discovered in Tomb 138 at Saobatang, Hunan dated to mid 4th century BC. Repeating crossbows, first mentioned in the Records of the Three Kingdoms, were discovered in 1986 in Tomb 47 at Qinjiazui, Hubei dated to around 4th century BC. The earliest Chinese document mentioning a crossbow is in scripts from the 4th–3rd century BC attributed to the followers of Mozi. This source refers to the use of a giant crossbow in 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.

The earliest textual evidence of the handheld crossbow used in battle dates to the 4th century BC. Handheld crossbows with complex bronze trigger mechanisms have also been found with the Terracotta Army in the tomb of Qin Shihuang (r. 221–210 BC) that are similar to specimens from the subsequent Han Dynasty (202 BC–220 AD), while crossbowmen described in the Han Dynasty learned drill formations, some were even mounted as cavalry units, and Han Dynasty writers attributed the success of numerous battles against the Xiongnu to massed crossbow fire.

According to Needham, 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.

Ancient Greece


The earliest reasonably reliable date for the crossbow in the Greek world is from the 5th century BC. 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 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. The gastraphetes was powered by a composite bow. It was cocked by resting the stomach in a concavity at the rear of the stock and pressing down with all strength. In this way considerably more energy can be summoned up than by using only one arm of the archer as in the hand-bow. The heavy weight and bulk of the gastraphetes necessitated a prop to keep it standing, i.e. by mounting it on a defensive wall or using a portable prop.

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 missiles at once.

From the mid-fourth century BC onwards, evidence of the Greek use of crossbows becomes more dense and varied: Arrow firing machines (katapeltai) are briefly mentioned by Aeneas Tacticus in his treatise on siegecraft written around 350 BC. An Athenian inventory from 330-329 BC includes catapults bolts with heads and flights. Arrow firing machines in action are reported from Philip II's siege of Perinthos in Thrace in 340 BC. At the same time, Greek fortifications began to feature high towers with shuttered windows in the top, presumably to house anti-personnel arrow shooters, as in Aigosthena.

The transition to the torsion catapults, which are not considered crossbows and came to dominate Greek and Roman artillery design is first evident in inventories of the Athenian arsenal from between 338 and 326 BC. Torsion weapons, which rely on the energy generated from twisted animal sinew became siege weapons and light artillery - such as the Greek ballista or the Roman scorpion.

In Roman times the crossbow became to be known as arcuballista.

Roman Empire


Besides the gastraphetes, the ancient world knew a variety of mechanical hand-held weapons similar to the later medieval crossbow. The exact terminology is a subject of continuing scholarly debate. Greek and Roman authors like Vegetius (fl. 4th century) note repeatedly the use of arrow firing weapons such as arcuballista and manuballista respectively cheiroballistra. While most scholars agree that one or more of these terms refer to handheld mechanical weapons, there exist disagreement whether these were flexion bows or torsion powered like the recent Xanten find. The Roman commander Arrian (ca. 86 - after 146) records in his Tactica Roman cavalry training for firing some mechanical handheld weapon from horseback. Sculptural reliefs from Roman Gaul depict the use of crossbows in hunting scenes. The specimen are remarkably similar to the later medieval crossbow, including the typical nut lock (see image).

Medieval Europe


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 achieves comparable accuracy and faster shooting rate than an average crossbow, crossbows release more kinetic energy and can be used effectively after a week of training, while a comparable single-shot skill with a longbow takes 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 more powerful 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.

Elsewhere


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&mdash;often wood, horn and sinew&mdash;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 served as a scouting 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.

Hunting, leisure and science


Crossbows are used for target shooting and bowhunting in modern archery and for blubber biopsy samples in scientific research.

Modern military and paramilitary use
In the Americas, the Peruvian army (Ejército) equips some soldiers with crossbows and rope, to establish a zip-line in difficult terrain. In Brazil the CIGS (Jungle Warfare Training Center) also trains soldiers in the use of crossbows. In the United States, SAA International Ltd manufacture a 150 ft/lb crossbow-launched version of the U.S. Army type classified Launched Grapnel Hook (LGH), amongst other mine countermeasure solutions designed for the middle-eastern theatre. It has been successfully evaluated in Cambodia and Bosnia. It is used to probe for and detonate tripwire initiated mines and booby traps at up to 50 meters. The concept is similar to the LGH device originally only fired from a rifle, as a plastic retrieval line is attached. Reusable up to 20 times, the line can be reeled back in without exposing oneself. The device is of particular use in tactical situations where noise discipline is important.

In Europe, British based Barnett International supplied crossbows to Serbian forces which according to The Guardian were later used "in ambushes and as a counter-sniper weapon", against the Kosovo Liberation Army during the Kosovo War in the areas of Pec and Djakovica, south west of Kosovo. . Whitehall launched an investigation, though the department of trade and industry established that not being "on the military list" crossbows were not covered by such export regulations. Paul Beaver of Jane's defence publications commented that, "They are not only a silent killer, they also have a psychological effect". On February 15, 2008 Serbian Minister of Defence Dragan Sutanovac was pictured testing a Barnett crossbow during a public exercise of the Serbian army's Special Forces in Nis, 200 km south of capital Belgrade. Special forces in both Greece and Turkey also continue to employ the crossbow. Spain's Green Berets still use the crossbow as well.

In Asia, Chinese armed forces use crossbows at all unit levels from traffic police to the special forces units of the People's Liberation Army. One justification for this comes in the crossbow's ability to stop persons carrying explosives without risk of causing detonation. Furthermore, during the Xinjiang riots of July 2009, crossbows were used alongside modern military hardware to quell protestors. Indian Navy's Marine Commando Force were equipped until the late 1980s with crossbows supplied with cyanide-tipped arrows, as an alternative to suppressed handguns.

Comparison to conventional bows
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, but there would be reduced elastic hysteresis, making the crossbow a more accurate weapon.

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.

Legal issues


Can. 29 of the Second Lateran Council under Pope Innocent II in 1139 may have banned the use of crossbows against Christians. The authenticity, interpretation and translation of this source is contested. Military historian K.C. Eyre suggested in an unpublished paper that the more probable explanation was a ban on William-Tell-like marksmanship demonstrations, in which people would shoot apples off head, etc. Given the high-risk nature of this sport, it is easy to see why the Church might discourage it. Given the generally nasty nature of conflict at the time, and the proliferation of ballistic, blunt and edged weapons in use, it is harder to see why the Church would have singled out the crossbow in particular as unsuitable.

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. Within the United States, regulations vary by state. Hunting is allowed in some states by persons with physical limitations that causes them to be unable to draw a conventional bow. In general, hunting regulations are being progressively relaxed.