Torsion siege engine

A torsion siege engine, or simply a torsion engine, is a kind of catapult and a siege engine, which uses torsion power to propel the projectiles. Some examples of torsion siege engines are the onager and the ballista. The first torsion siege engines were developed by the ancient Greeks^[1]. Later on, they were partially replaced by the trebuchet in the Middle Ages; then all catapults were gradually replaced by the cannon in the 14th century^[2].

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