What armored Leonardo da Vinci invention was designed to move using hand-operated cranks?

Leonardo da Vinci designed an armored fighting vehicle intended to move using hand-operated cranks.

The vehicle appears in Leonardo’s military engineering studies from the late 15th century. It had a conical, turtle-like armored shell with sloping plates, an arrangement that could deflect incoming projectiles. Cannons were positioned around the lower edge so the crew could fire in several directions.

The design is often called Leonardo’s tank, but it was not a modern tank and was never built for Renaissance warfare. The gearing shown in the surviving drawing would make the vehicle difficult or impossible to propel as presented, possibly because of an error, a deliberate flaw, or an unfinished design. Leonardo prepared military projects for patrons such as Ludovico Sforza, combining defensive armor, artillery, and mechanical engineering.