Leonardo da Vinci sketched an armored tank with sloped armor and internal hand cranks.
The fighting vehicle appears in a design generally dated to about 1487, when Leonardo was working for Ludovico Sforza in Milan. Its conical, turtle-like shell was intended to deflect incoming projectiles, while a group of men inside would turn cranks connected to the wheels. The vehicle also carried several light cannons around its perimeter.
The machine was never built in Leonardo's lifetime. Some modern accounts claim that a deliberate gear error prevented construction, but historians have debated whether the apparent flaw was simply a drawing or copying problem. A full-sized replica was constructed for a 2006 television documentary.
Calling it a tank is convenient but anachronistic: the word and modern tracked armored vehicle belong to the twentieth century. Leonardo's design was a wheeled armored fighting vehicle intended for siege warfare.