Greek catapults grew from bows, and turned engineering into science
A catapult hurls things without any gunpowder, storing energy slowly in bent bows, springs or twisted rope and releasing it all at once. Greek engineers began by beefing up the humble bow. Within two centuries they had a formal theory scaling every part of the machine to the size of its torsion springs.
Machines for throwing heavy objects are old. King Uzziah of Judah reportedly mounted devices on Jerusalem's walls that shot great stones, which would date catapults to at least the seventh century BC. The Yajurveda mentions them under the name jyah, and Ajatashatru of Magadha is credited with using them against the Licchavis in the fifth century BC, the same century the mangonel, a pulled-rope traction machine, appeared in China. The English word travels through Latin from a Greek term combining down and to hurl.
In Greece the story is tied to the crossbow. An early foot-braced weapon, the gastraphetes or belly-bow, stored more energy than an ordinary bow and apparently inspired later machines. A southern Italian engineer named Zopyrus designed advanced versions, probably for sieges between 421 and 401 BC, with winches to draw the string and the ability to loose two missiles together. According to Diodorus Siculus, a Greek task force built a mechanical arrow-shooter in 399 BC and used it two years later against Motya, a Carthaginian stronghold in Sicily.
The decisive change came with torsion. An Athenian arsenal inventory, carved sometime between 338 and 326 BC, records catapults with springs made of sinew, the first clear sign of torsion machines, which outperformed flexible bow designs and dominated Greek and Roman artillery afterwards. Engineers serving Philip II of Macedon probably drove the switch. Onomarchus of Phocis became the first to use catapults on an open battlefield, against Philip, and Alexander the Great later did so at the Jaxartes as well as in sieges.
Training spread with the weapon: a third-century BC inscription from the Aegean island of Ceos regulated catapult shooting contests for young people. Around 200 BC Philo of Byzantium set out belopoietics, the art of making projectile weapons, based on proportion. Today the word stretches from a hand-held slingshot to the machinery that launches aircraft off a ship's deck.
Source: Catapult
