What did Leonardo da Vinci design in 1488 as a military armored vehicle powered by eight men?

Leonardo da Vinci designed the fighting vehicle in 1488 as a military armored vehicle powered by eight men.

The design resembles a low, conical tortoise covered with armor plates. Inside, a crew would turn cranks connected to gears, driving the vehicle's wheels. Small cannons projected through openings around its perimeter, allowing it to fire in several directions.

Leonardo probably intended the machine as a proposal for Ludovico Sforza, the ruler of Milan, whose court supported military engineering. The vehicle was never built in Leonardo's lifetime, so it remained a design rather than a proven battlefield machine.

A famous modern observation is that the surviving drawing contains a gear arrangement that would make the vehicle difficult or impossible to move as shown. Some historians interpret this as an intentional error protecting Leonardo's idea, while others regard it as a design mistake. It is often called Leonardo's tank, although that modern term did not exist in his period.