The gastraphetes (from Ancient Greek γαστραφέτης, English translation: "belly-releaser") was a hand-held crossbow used by the Ancient Greeks.[1]It was described in the 1st century AD by the Greek author Heron of Alexandria in his work Belopoeica, which draws on an earlier account of the famous Greek engineer Ctesibius (fl.285-222 BC). Heron identifies the gastraphetes as the forerunner of the later catapult, which places its invention some unknown time prior to ca. 420 BC.[2]

Unlike later Roman and medieval crossbows, spanning the weapon was not done by pulling up the string, but by pushing down an elaborate slider mechanism.A fairly detailed description and drawing of the gastraphetes appears in Heron's Belopoeica (Ancient Greek Βελοποιικά, English translation: On arrow-making), drawn from the account by the 3rd century BC engineer Ctesibius. The weapon 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.

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. According to some authors, the dimensions of the gastraphetes may have involved some kind of prop.[3]

A larger version of the gastraphetes were the oxybeles, which were used in siege warfare. These were later supplanted by the early ballistae that later also developed into smaller versions supplanting also the gastraphetes.According to a long dominant view expressed by E. W. Marsden, the gastraphetes was invented in 399 BC by a team of Greek craftsmen assembled by the tyrant Dionysius I of Syracuse.[4]However, recent scholarship has pointed out that the historian Diodorus Siculus (fl. 1st century BC) actually did not mention the gastraphetes, but was referring to the invention of the "katapeltikon", a mechanical arrow firing catapult.[3][5]Since Heron states in his Belopoeica that stand-mounted mechanical artillery such as the katapeltikon was inspired by the earlier hand-held gastraphetes, the invention of handheld crossbows into Greek warfare must have thus occurred some unknown time before 399 BC.[3]

The terminus ante quem may be more precisely defined as being before 421 BC, since another Greek author, Biton (fl. 2nd c. BC), whose reliability has been positively reevaluated by recent scholarship,[6]credits two advanced forms of the gastraphetes to a certain Zopyros. This Zopyros was probably a Pythagorean engineer from southern Italy.[7][8]He may have designed his stand-mounted bow-machines on the occasion of the sieges of Cumae and Milet between 421 BC and 401 BC, thus marking the date by which the archetypical gastraphetes must have already been known.[9]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 AD) 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.[10]
• The Roman commander Arrian (ca. 86-after 146 AD) records in his TacticaRoman cavalry training for firing some mechanical handheld weapon from horseback.[11]
• Sculptural reliefs from Roman Gaul depict the use of crossbows in hunting scenes. Dating to the 1st-2nd century AD, the specimen are remarkably similar to the later medieval crossbow, including the typical nut lock. From their reflexible shape they were composite bows.[12][13]

The first catapults were invented by the Greeks around 400 BC. These catapults called gastraphetes resembled large crossbows and were used to shoot darts or arrows. By about 330 BC a larger version was developed. Called a ballista and using torsion to propel a dart or arrow, this machine could take out several armored men with one shot. This type of catapult was used by Alexander the Great on his campaigns.

The Romans used the Greek catapult technology and built upon it. They developed the mangonel, also called the onager. The word mangonel means engine of war. The firing of the mangonel resembled the kick of a wild donkey, called an onager, hence the nickname onager for the mangonel. The mangonel was also propelled by torsion. The Romans made it bigger, stronger, and easier to move from place to place.

Other types of catapults were soon developed. The traction trebuchet used a flexible throwing arm to fling stones at the enemy. It was held in place by two or three men while a few more bent the arm back, loaded it, and released it. It was lightweight and very mobile, but could only be used for small projectiles. Over time this traction trebuchet was made larger and placed on a cart with wheels. It was used to in the Middle Ages to defend a castle and to lay siege to one. It could be used to throw flaming balls over castle walls which would explode upon impact setting fire to the people, animals, and structures inside.

The counterweight trebuchet was the most destructive type of catapult. It could be used to launch bigger, heavier projectiles from a safe distance. Its main drawback was that it is not mobile. It was too large to transport, and wheels would hinder its performance. It had to be built on site. It was also too large for castle defense, both because of space limitations and the fact that it would throw a projectile too far -- over the heads of the besiegers. Historically it was used to hurl dead horses, corpses, and other things that would smell and spread disease over castle walls to force those holed up inside to surrender.

For several centuries after the invention of gunpowder, the catapult fell into disuse. It has, however, found some modern uses. A very simple catapult used as a children's toy -- the slingshot, was popular for a time. Catapults were also used in early aviation to try to launch some of the first airplanes. Samuel P. Langley used a spring-powered catapult to propel his Aerodrome with enough speed to get it into the air. The Wright brothers used a version of the counterweight trebuchet to generate enough speed to lift an aircraft and propel it until the engines could take over. In World War I and World War II small catapults were used to launch grenades at the enemy. Today catapults are used to launch aircraft from the decks of aircraft carriers and built by engineering students and enthusiasts to launch everything from pumpkins to people.