Leonardo da Vinci’s armored military vehicle sketch is commonly called a tank.
Leonardo designed the conical armored vehicle around 1487, probably while seeking military patronage from Ludovico Sforza in Milan. Its sloping shell was intended to deflect incoming projectiles, while a ring of small cannons projected through openings around the vehicle.
The design was powered by people turning internal cranks connected to wheels. In its surviving form, the gear arrangement would make the vehicle move backward, but historians commonly regard that as a copying or drawing error rather than the intended engineering solution.
Leonardo’s vehicle was not a modern tank and was never built for battlefield service. Modern tanks appeared centuries later, during the First World War. The famous sketch is therefore best understood as an early concept for an armored fighting vehicle, not a working tank.