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Catapults are siege engines using an arm to hurl a projectile a great distance. Any machine that hurls an object can be considered a catapult, but the term is generally understood to mean medieval siege weapons.

Catapults were usually assembled at the site of a siege, and an army carried few or no pieces of it with them.


Catapults can be classified according to the physical concept used to store and release the energy required propel the projectile.

The first catapults were tensional catapults, developed from the Roman ballista. A member under tension propels the throwing arm, very much like a giant crossbow. A small simple version is used as a toy.

Subsequently, torsional catapults were developed, such as the mangonel and the onager. Mangonels have an arm with a bucket or cup to hold the projectile at one end. The bottom end of the throwing arm is inserted in rope or fibers that are twisted, providing the force to propel the arm.

The most sophisticated catapult is a trebuchet, which uses gravity rather than tension or torsion to propel the throwing arm. A falling counterweight pulls down the bottom end of the arm and the projectile is thrown from a bucket attached to a rope hanging from the top end of the arm, essentially like a sling attached to a giant see-saw.


The first catapults appear in later Greek times, early adopters being Dionysius of Syracuse and Onomarchus of Phocis. Alexander the Great introduced the idea of using them as cover on the battlefield as well as in sieges.

Catapults were more fully developed in Roman and Medieval times, the trebuchet being introduced a relatively short-time before the advent of gunpowder, which made the catapult more or less obsolete.

See also

The name catapult is also given to devices used to launch aircraft off ships, in particular aircraft carriers.

Up to and during World War II most such catapults were hydraulic. After the war navies gradually converted to steam catapults, which were the only ones capable of launching the heavier jet fighters. At the beginning of the 21st century, navies started experimenting with catapults powered by linear induction motors and electromagnetics.