A Roman legion (from Latin legio "military levy, conscription", from legere "to choose") was the largest unit of the Roman army involving from 3000 men in early times to over 5200 men in imperial times, consisting of centuries as the basic units. Many of the legions founded before 40 BC were still active until at least the fifth century, notably Legio V Macedonica, which was founded by Augustus in 43 BC and was in Egypt in the seventh century during the Islamic conquest of Egypt.