Leonardo da Vinci designed an early tank concept as a covered, armored wagon with guns.
The design appears in Leonardo's notebooks from around 1487–1490, during his service to Ludovico Sforza in Milan. It used a conical cover inspired partly by a tortoise shell and included multiple gun openings around the vehicle. Crew members inside would turn cranks connected to wheels.
Leonardo's fighting vehicle was never built in his lifetime, and the design contains a famous technical problem: some drawings show the gears arranged so the vehicle would move backward rather than forward. Historians debate whether this was an error, deliberate sabotage, or an intentional safeguard. It is often called a tank, but it was not a modern tracked tank; it had wheels and no internal combustion engine.