A crossbow is an ancient weapon, composed of a bow mounted on a stock that launches projectiles, known as bolts. A mechanism in the stock allows the bow to be in its fully-drawn position at all times. The crossbow is fully-drawn until it is shot by releasing a trigger. These dangerous weapons are known for their role in Asian and European warfare. Today however, crossbows are mainly used for target shooting and sport hunting. It is likely that the crossbow was first used by tribes of South-Eastern Asia, where today it is still used by the hunter-gatherer and nomad tribes, both for hunting, warfare, and "toys".



Gastraphetes, the Greek version of the crossbow, was used in various Greek wars and seiges, and was used extensively by the army of Dionysius during the siege of the city Motya, (a fundamental stronghold in Sicily), in 397 BC. Sun Tzu consistently comments on the use of the crossbow, and less than fifty years from the siege of Motya, in 341 BC, there are records of crossbows being employed in the Battle of Ma-Ling. By 200 BC, the crossbow was a popular weapon in China, and have been found with soldiers of the Terracotta Army in the tomb of the Chinese emperor Qin Shi Huang (260-210 BC).

In the Finnish national epic, Kalevala, Joukahainen is shown ambushing the hero V'in?m'inen with a crossbow. The legendary hero of Switzerland, William Tell, shot an apple from the top of his own son's head using a crossbow. Later on, William Tell began the war of liberation by ambushing the Vogt Gessler. The bow part (refered to as a prod or lath) of early crossbows were made only of one piece of wood, mainly crafted of ash or yew. Later on Europeans were exposed to "Saracen composite bows" which were crafted from layers of various materials, like wood, horn and sinew. These layers were then glued together and bound with animal tendon. The Saracen composite bows were considered much more powerful than the wooden bows the Europeans used. And the materials used by the Saracen composite bows were widely adopted and utilized by the Europeans. Later, as steel became more widespread, the Europeans started creating spring steel prods. Because of the crossbow's short draw length, they are less efficient at releasing a powerful projectile and to compensate for this, crossbows must have heavy draw weights.

While many crossbows are drawn using the arm strength of an archer, crossbows that release much more powerful projectiles require some sort of mechanical device to draw the string. These mechanisms were created out of a range of devices, some utilizing levers, ratchets and pulleys in complicated ways. These mechanisms allowed soldiers to use and shoot weapons with a draw force far greater than what could have been handled with a normal bow. Later on, the crossbow had enough draw force to penetrate any chainmail and nearly all plate armor: some crossbows had a draw force of nearly 350 lbf, compared to the 60-180 lbf draw force of a longbow.

The prod was often lashed to the stock with rope, whipcord, or other strong cording. This cording is called the "bridle" of the crossbow. Similar to a horse's bridle, it tends to loosen over time, and must be carefully re-bound.

The strings for a crossbow are typically made of strong fibers that cannot fray. According to W. F. Patternson, whipcord was very common while linen, hemp, and sinew were also used. Sometimes, in wet conditions, the strings were even made out of twisted mulberry root.

The mechanism that holds the drawn bowstring is called a nut, and was usually crafted out of bone, ivory or metal. The trigger, originally refered to as the "tricker", was crafted of metal. Bronze triggers with safety notches are known to have been used as early as 200 BC. There are more complicated iron triggers designed in Europe by the 1400s. The famous Leonardo da Vinci designed many trigger mechanisms.