What Leonardo da Vinci war-machine concept had a circular armored body and many cannons?

Leonardo da Vinci’s circular armored war-machine concept is commonly called Leonardo’s tank.

Leonardo designed the fighting vehicle in the late fifteenth century, probably around 1487–1490. Its conical cover resembled a turtle shell and was intended to protect soldiers inside. The platform carried numerous light cannons arranged around the perimeter, allowing fire in several directions while the vehicle advanced across a battlefield.

The vehicle was to be moved by cranks connected to internal gears. Modern reconstructions have noted that the original gear arrangement appears to contain a deliberate or accidental flaw that would prevent straightforward movement. Some historians have suggested that Leonardo may have inserted the problem to keep the military design from being used, but his exact intention is not known.

Calling it a tank is convenient but retrospective. It was not an engine-powered armored vehicle like a twentieth-century tank. Its importance lies in the attempt to combine armor, mobility, and concentrated firepower in one machine.