What movable fortress did Leonardo da Vinci design with sloped walls to deflect attacks?

Leonardo da Vinci’s movable fortress with sloped walls was an armored fighting vehicle.

Leonardo designed the vehicle in the late fifteenth century for his patron Ludovico Sforza, duke of Milan. The machine had a conical, turtle-like shell made from angled armor plates. Several cannons were positioned around the lower edge so the vehicle could fire in multiple directions while protecting the crew inside.

The vehicle was intended to move using cranks connected to wheels and gears operated by people inside. Its sloped surfaces could help deflect incoming projectiles, a principle later associated with armored vehicles. Leonardo’s drawing is often called a tank, but that term belongs to modern military technology and was not used in his period.

Historians have debated whether the mechanism as drawn would move effectively, because some gear arrangements appear inconsistent. It is therefore safest to call it a design for an armored fighting vehicle, not a proven working tank. No evidence shows that Leonardo built or deployed it in battle.