Leonardo da Vinci’s circular armored fighting machine was Leonardo’s tank.
Leonardo designed the vehicle in the 1480s, probably for presentation to Ludovico Sforza, the Duke of Milan. Its conical cover resembled a tortoise shell and was reinforced with metal plates. The vehicle also included a ring of light cannons around its perimeter, allowing defenders to fire in several directions.
The machine was meant to be moved by cranks operated by people inside. A famous drawing contains a gear arrangement that appears unable to make the wheels turn correctly, leading to the suggestion that Leonardo deliberately inserted a flaw so the design could not easily be copied. Historians debate whether the problem was intentional or simply a design error.
It was never built or used in battle during Leonardo’s lifetime. The vehicle is often called a tank because its armor and battlefield role resemble later armored vehicles, although it had no engine, turret, or modern tracked system.