Leonardo da Vinci designed a giant crossbow as a large-scale military weapon.
His drawing, dated around 1488–1489, shows an enormous bow mounted on a wheeled frame. The design used a winch or similar mechanism to draw the bowstring, because a person could not pull such a powerful bow by hand. Its broad bow was intended to launch unusually large stones or bolts.
The crossbow is preserved in Leonardo’s Codex Atlanticus. It was probably a proposal rather than a completed battlefield machine. Leonardo often enlarged familiar weapons in his military studies to increase psychological impact as well as destructive power.
It is sometimes confused with a ballista, but the giant crossbow uses a bow and string, while a ballista is a torsion-powered engine. No surviving evidence shows that Leonardo’s particular design was built or successfully tested.