What military vehicle did Leonardo da Vinci design as a precursor to the modern tank?

Leonardo da Vinci designed an armored vehicle often regarded as a precursor to the modern tank.

His c. 1487 drawing shows a conical, turtle-like armored shell mounted on wheels. The vehicle was intended to protect soldiers while carrying weapons, including cannons, around its perimeter. Its sloped covering could also help deflect incoming projectiles.

The design was not built for Leonardo’s military patrons. The vehicle contains a famous mechanical problem: the internal crank arrangement, as commonly drawn, would make the wheels turn in conflicting directions. Historians debate whether this was an intentional secret error or simply an unfinished design.

Calling it a tank is convenient but historically imprecise. Modern tanks depend on engines, tracks, armor systems, and battlefield tactics developed centuries later. Leonardo’s machine is better understood as an ingenious armored fighting-vehicle concept.