Leonardo da Vinci’s covered, circular fighting vehicle is commonly called the armored tank.
Leonardo designed it in the late 15th century for Ludovico Sforza, the ruler of Milan. The vehicle had a conical armored shell inspired partly by a tortoise, sloping plates intended to deflect attacks, and several light cannons around its lower edge. Inside, men would turn cranks connected to wheels to move the machine.
The design was not built for Renaissance warfare. A frequently repeated story says Leonardo intentionally included a gearing error to prevent the vehicle from being constructed, but historians debate whether the apparent problem was deliberate or simply a drawing error. The design also had practical weaknesses, including its heavy weight and limited mobility.
Calling it a “tank” is modern terminology. Leonardo did not use the word in the modern military sense, and his machine was a drawing rather than an operational armored vehicle. It nevertheless anticipated several features later associated with tanks: armor, wheels, enclosed crew space, and mounted guns.