What wheeled military machine did Leonardo da Vinci design with an armored conical cover?

Leonardo da Vinci designed an armored vehicle, often called Leonardo’s fighting vehicle, with a covered conical body and weapons.

The vehicle was drawn around 1487–1488 while Leonardo worked for Ludovico Sforza in Milan. Its sloped armored shell was intended to deflect enemy fire, and the platform included openings for cannons. The machine also had wheels and was meant to move across a battlefield while protecting the crew.

A famous feature is a set of internal gears connected to the wheels. In the surviving drawing, those gears appear to be arranged incorrectly, so the vehicle could not operate as shown. Some historians think this may have been an intentional flaw designed to keep the military idea private. Although it is popularly called a tank, it was never built or used in warfare, and it lacked the engine and mechanical systems of modern tanks.