Leonardo da Vinci designed an armored tank with sloped armor and internal hand cranks.
His fighting vehicle appears in drawings from around 1487–1488. The conical, turtle-like machine was covered by sloped armor intended to deflect enemy fire. Several men inside would turn cranks connected to wheels, moving the vehicle across the battlefield.
The design carried light cannons around its perimeter, giving occupants the ability to fire in multiple directions. Leonardo presented the concept as a military machine, probably in material prepared for the Duke of Milan, Ludovico Sforza.
A famous drawing shows a mechanical problem: the gearing appears to make the wheels turn in opposite directions. Some historians think this was deliberate, perhaps to conceal the design from potential rivals; others regard it as an error. Because no contemporary prototype is known, the vehicle was a concept rather than a deployed tank. Its shape nevertheless anticipates important features of later armored fighting vehicles.