Which Leonardo da Vinci design is often described as an early armored fighting vehicle?

Leonardo da Vinci's early armored fighting vehicle is commonly called Leonardo's tank.

Leonardo designed the vehicle around 1487 for his patron Ludovico Sforza, the Duke of Milan. The drawing shows a conical, turtle-like armored cover fitted with guns around its perimeter. Inside, men would turn cranks connected to wheels, allowing the vehicle to move across a battlefield while shielding its crew from enemy fire.

The machine was never completed or used in war. A frequently repeated story says Leonardo deliberately included a flaw in the gearing to prevent the design from being used by hostile forces, but historians debate whether the apparent problem was intentional or simply a design error. The vehicle also lacked a practical engine and would have been extremely difficult to move.

Despite those limitations, the concept anticipates several features associated with later tanks: armor, all-around weapons, and protected crew members. The modern word “tank” was not used for this Renaissance machine; it is a later descriptive label applied because of its enclosed armored form.