A crossbow is a modified bow with added mechanism for string release. The oldest crossbows were found among State of Chu relics, dating back to the 6th century BC; they were used for battle, but also as mechanical traps. In Greece, the crossbow may have already been in use around the same period, or perhaps earlier. While the general idea of a crossbow remained the same, its design varied and evolved throughout the ages, being employed by the Imperium Romanum, in Medieval Europe and Asia, and also by Africans and Inuits. It was the evolution of guns which gradually ended military use of crossbows, but they remained in use as sporting, hunting, and scientific equipment.