Leonardo da Vinci designed catapult mechanisms that used stored spring energy to throw large projectiles.
His notebooks include studies of siege engines with powerful wooden arms, springs, winches, and locking devices. The spring stored energy while the machine was drawn back; releasing the arm transferred that energy to a stone or other projectile.
Leonardo’s catapult was an improved Renaissance design rather than a wholly new invention. Ancient armies had used catapults for centuries, and medieval engineers continued to modify them. Leonardo focused on mechanical efficiency, compactness, and the controlled release of stored force.
A catapult is often confused with a trebuchet. A catapult is a broad category of projectile-launching engines, while a trebuchet specifically uses a pivoted beam and usually a counterweight or traction system. Leonardo also studied other siege weapons, including giant crossbows.