What military vehicle did Leonardo da Vinci design with sloped protective armor?

Leonardo da Vinci designed an armored vehicle with sloped protective armor.

His 1487 drawing shows a conical, covered vehicle resembling a turtle shell. The outer surface was intended to deflect incoming weapons, while several men inside would turn cranks connected to wheels. The vehicle also included openings for light cannons.

Modern writers often call the design Leonardo’s tank, but that label can be misleading. It was not powered by an engine, and it was never built for Renaissance warfare. The proposal was a mobile armored fighting machine driven by human muscle.

A famous feature of the drawing is an apparent gear arrangement that would prevent the wheels from turning in the intended direction. Historians debate whether this was an error, a deliberate flaw, or evidence that the design was not meant to be constructed exactly as drawn. Its sloped armor remains a striking anticipation of a feature used by later armored vehicles.