Leonardo da Vinci designed a fighting vehicle with a conical armored body and internal wheels.
The vehicle is commonly described as an early tank concept. Its sloped outer shell was intended to deflect incoming attacks, while cannons projected through openings around the perimeter. Inside, operators would turn cranks connected to gears and wheels to move the machine.
The design appeared in Leonardo's military notebooks, probably in the late 15th century, when Italian states were developing artillery and fortified warfare. It was never documented as a completed battlefield vehicle. The proposed gearing also creates a famous mechanical problem: some modern interpretations find that the gear arrangement would make the vehicle move backward unless corrected.
That apparent flaw may have resulted from an intentional alteration in the drawing, an error, or a design that was never fully engineered. In any case, the vehicle shows Leonardo combining armor, mobility, and concentrated firepower in one concept.