What defensive vehicle did Leonardo da Vinci design with a conical armored shell and internal wheels?

Leonardo da Vinci designed a fighting vehicle, an armored machine often described as an early tank concept.

The vehicle appears in Leonardo's notebooks from the late 15th century. Its conical cover was intended to deflect incoming projectiles, while several crew members inside would turn cranks connected to the wheels. The design was not built as a practical battlefield vehicle during Leonardo's lifetime.

The machine is sometimes called Leonardo's tank, but that wording can mislead readers because modern tanks use engines, tracks, turrets, and heavy armor. Leonardo's design used human power and wheels. A commonly noted problem is that the original gear arrangement would have made the machine difficult or impossible to move unless corrected.

Its importance lies in the combination of armor, mobility, and offensive capability. It shows Leonardo thinking about battlefield engineering as an integrated mechanical system, rather than merely sketching a protective shell.