Leonardo da Vinci redesigned a catapult with a giant spring to store and release energy.
His military notebooks contain studies of spring-powered throwing machines. In one design, a large flexible element was drawn back and released to propel a projectile. Leonardo examined the geometry and mechanics of the device in detail, seeking greater power and a more controlled launch than a simple lever could provide.
A catapult is a siege engine that throws a projectile without using explosive propellant. Different historical catapults used different power sources, including torsion, tension, and gravity. Leonardo’s spring-based concept therefore belongs to the broad catapult family but is not identical to every ancient or medieval machine called a catapult.
There is no strong evidence that Leonardo’s redesigned version became a standard battlefield weapon. His drawings are best regarded as engineering studies exploring how stored mechanical energy could be converted into motion.