Leonardo da Vinci designed an armored tank, also called a fighting vehicle, with a conical protective shell and internal wheels.
Leonardo drew the vehicle in the Codex Arundel and related notebooks around 1487. Its sloped covering was intended to deflect enemy projectiles, while several crew members inside would turn cranks connected to the wheels. The vehicle was meant to carry small guns around its perimeter and advance across a battlefield.
The machine was never built for Leonardo’s patron, Ludovico Sforza, and no evidence shows that it entered military service. Modern descriptions sometimes call it a tank, but that is a retrospective label: the tank as a powered armored fighting vehicle appeared during the First World War, more than 400 years later.
A famous detail is a supposed flaw in the drawing: the internal gears appear arranged so the vehicle could not move. Some historians think this was an intentional concealment or drafting error; others regard it as an unresolved engineering problem.