Leonardo da Vinci designed an armored tank with sloped armor and many gun openings.
His fighting vehicle was a conical, turtle-like structure mounted on wheels. The sloping outer shell was intended to deflect incoming projectiles, while a ring of light cannons around the lower edge would allow the crew to fire in several directions. The design is usually dated to about 1487–1489.
Inside, men would turn cranks connected to the wheels. Modern reconstructions often point out that the surviving drawing appears to contain a gearing problem that would make the vehicle move backward if built exactly as shown. Historians disagree about whether that was a deliberate security measure, a drafting error or an untested mechanical detail.
Calling it a modern tank is convenient but anachronistic. It had armor, wheels and onboard weapons, yet lacked an engine, a rotating turret and the battlefield systems associated with twentieth-century tanks. Leonardo proposed it as a military machine, not as a working vehicle that he demonstrated.