What Leonardo da Vinci design is commonly regarded as an early tank concept?

Leonardo da Vinci’s armored vehicle is commonly regarded as an early tank concept.

He designed it in the 1480s for Ludovico Sforza, the ruler of Milan. The vehicle had a conical, turtle-like shell made from wooden plates reinforced with metal. Its sloping exterior was intended to deflect incoming missiles, while cannons around the platform would let the crew fire in several directions.

The vehicle was moved by people turning internal cranks connected to wheels. Some modern reconstructions have found that Leonardo’s original gearing would make the machine difficult or impossible to drive, possibly because of an error in the drawing or an intentional concealment of the design.

Unlike a twentieth-century tank, Leonardo’s vehicle had no engine, tracks or enclosed armored fighting compartment. It remains a notable example of Renaissance military engineering and the early idea of protected mobile artillery.