What military vehicle did Leonardo da Vinci sketch as a conical armored wagon?

Leonardo da Vinci sketched an armored tank, a conical armored wagon intended to move across a battlefield while protecting its occupants.

He designed the fighting vehicle around 1487 for Ludovico Sforza, the ruler of Milan. The machine had a broad, turtle-like shell, sloping armor, and openings for light cannons. Its shape was meant to deflect incoming weapons.

The vehicle was powered by men turning cranks connected to gears and wheels. A famous drawing appears to show the gears arranged incorrectly, making the vehicle unable to move. Some historians think this was an intentional error to keep the design secret; others view it as a genuine mechanical problem.

It was never built as a Renaissance weapon. The word “tank” is a modern comparison, since tracked armored vehicles appeared centuries later.