Leonardo da Vinci sketched an armored vehicle in 1487 with sloping armor and concealed wheels.
The vehicle was a conical, covered platform intended to move across a battlefield and provide protection for soldiers inside. Its armor was arranged at angles, a feature that could help deflect incoming projectiles. The design also included openings for weapons around the platform.
Modern writers often call it Leonardo’s tank, but that label is retrospective. It was not a modern tank, because it had no engine, continuous tracks or demonstrated ability to cross difficult terrain. The vehicle was powered in the drawing by cranks turned by people inside.
A famous detail is an apparent gearing problem that would make the vehicle move backward if the mechanism were built exactly as drawn. Historians debate whether this was a deliberate security measure, a drawing error or an incomplete design.