What Leonardo da Vinci military design had a conical, turtle-like armored body?

Leonardo da Vinci’s armored tank design had a conical, turtle-like body surrounded by cannon openings.

Leonardo drew the fighting vehicle in the 1480s while seeking military employment from Ludovico Sforza, Duke of Milan. The design showed a large covered platform with sloping armor and several light cannons projecting through openings. Men inside would turn cranks connected to wheels, allowing the vehicle to advance while protected.

The machine was not built as a Renaissance battlefield tank. Its exact practicality is debated because the vehicle would have been difficult to propel and coordinate. A commonly repeated story says Leonardo deliberately included a flaw in the gear system, but historians cannot establish that explanation with certainty.

The design nevertheless anticipated important features of later armored vehicles: crew protection, mobility, and weapons mounted around a covered hull. Modern tanks use engines, tracks, and turrets, none of which appear in Leonardo’s original concept.