What Leonardo da Vinci military invention is often described as an early tank?

Leonardo da Vinci’s fighting vehicle is often described as an early tank.

The design, created around 1487, was a covered, conical vehicle mounted on wheels. Its sloping armor was intended to deflect enemy fire, while openings around the lower edge would allow weapons to be used against opponents. Leonardo’s notes also envisioned the vehicle being powered by people inside it turning cranks.

The fighting vehicle was a design rather than a battlefield machine. A commonly discussed problem is that the gearing shown in some reconstructions would make the wheels turn in conflicting directions. Historians and engineers debate whether this was an intentional safety flaw, a drawing error, or an incomplete design.

Calling it a “tank” is a modern comparison. Leonardo’s vehicle lacked the engine, turret, and tracked system associated with modern tanks.