Roman legion

See List of Roman legions for a catalogue of known late republic, early Empire and late Empire legions, with dates in existence, emblem and locations of deployment.A Roman legion (from Latin legio ""military levy, conscription"", from legere ""to choose"") normally indicates the basic ancient Roman army unit recruited specifically from Roman citizens.In reference to the early Roman Kingdom (as opposed to the Roman Republic or empire), ""the legion"" means the entire Roman army. The subsequent organization of legions varied greatly over time but they were typically composed of around five thousand soldiers, divided into three lines of ten maniples during the republic, and later into ten cohorts during the early empire. Legions also included a small cavalry unit. By the third century, the legion was a much smaller unit of about 1,000 to 1,500 men, and there were more of them. In the fourth century, East Roman border guard legions (limitanei) may have become even smaller.For most of the Roman Imperial period, the legions formed the Roman army's elite heavy infantry, recruited exclusively from Roman citizens, while the remainder of the army consisted of auxiliaries, who provided additional infantry and the vast majority of the Roman army's cavalry. (Provincials who aspired to citizenship gained it when honorably discharged from the auxiliaries). The Roman army, for most of the Imperial period, consisted mostly of auxiliaries rather than legions.Twelve of the legions founded before Common Era were still active until at least the fifth century, notably V Macedonica which was founded by Augustus in 43 BC and was in Egypt in the seventh century during the Islamic conquest of Egypt.