Leonardo da Vinci designed a giant crossbow mounted on a wheeled frame as a military siege weapon.
The drawing shows an enormous bow set across a broad support structure, with wheels beneath it for transport and positioning. Leonardo’s notes and sketches indicate that the machine was intended to launch a large projectile, probably to intimidate an enemy and attack fortifications rather than to function like a handheld crossbow.
A crossbow stores energy by bending a bow and releases it through a trigger mechanism. Scaling that principle up created major engineering problems: the bow required enormous force to draw, the frame had to withstand the stored energy, and the machine needed a reliable loading system. Leonardo’s design therefore emphasizes mechanical aids and structural support.
There is no secure evidence that Leonardo’s giant crossbow entered regular service. It belongs to his large collection of military proposals, many of which combined dramatic visual impact with attempts to solve real problems of transport, force, and battlefield deployment.