The history of cannon spans several hundred years. First used in China, they were among the earliest forms of gunpowder artillery, and over time replaced siege engines—among other forms of aging weaponry—on the battlefield. The earliest known cannon was invented in Alexandria, in the 3rd century BC but very little is known about this. The world's earliest known cannon, dated 1282, was found in Mongol-held Manchuria. By the 1500s, cannon were made in a great variety of lengths and bore diameters, but the general rule was that the longer the barrel, the longer the range.