What fortified vehicle did Leonardo da Vinci design for battlefield use?

Leonardo da Vinci designed an armored tank as a fortified vehicle for battlefield use.

His concept, drawn around 1487, resembles a conical turtle shell mounted on a wheeled platform. The sloped exterior was intended to deflect attacks, while cannons around the lower edge could fire in multiple directions. Crews inside would turn cranks connected to the wheels.

The vehicle was never built for Renaissance warfare, and it would have faced serious practical problems. Its heavy armor demanded more power than the proposed human-driven mechanism could likely supply. Some historians have also discussed whether an apparent design inconsistency was deliberate or simply an error in the drawing.

Leonardo’s machine was not a modern tracked tank. The word tank later came to describe armored military vehicles with powered propulsion and, usually, continuous tracks.