What military vehicle did Leonardo da Vinci sketch with conical armor and internal wheel mechanisms?

Leonardo da Vinci sketched an armored fighting vehicle with conical armor and internal wheel mechanisms.

The vehicle appears in Leonardo’s notebooks from the late fifteenth century. Its sloping armor was intended to deflect projectiles, while several cannons were arranged around the broad lower structure. The crew would turn internal cranks connected to the wheels.

Modern writers often call it Leonardo’s tank, although the word “tank” belongs to twentieth-century armored warfare. A famous reconstruction problem shows the original drawing with gears that would make the vehicle move backward if copied literally. Some historians interpret that as an error; others have suggested it could have been deliberate, since Leonardo sometimes concealed or complicated military designs. No evidence shows that the vehicle was built in his lifetime.