Legion

Legion, in the Roman military system, corresponded in force and organisation to what in modern times we should call a corps d'armée. It differed in constitution at different periods of Roman history. In the time of the republic a legion comprised 4500 men, thus divided: 1200 hastati, or inexperienced troops; 1200 principes, or well-trained soldiers; 1200 velites, or skirmishers; 600 triarii, or pilani, veterans forming a reserve; and 300 equites, knights who acted as cavalry, and belonged to families of rank. During this period the legions were formed only for the season; standing armies being of later growth. The hastati, principes, and triarii formed three separate lines, each divided into 10 maniples or companies, of 120 men each in the case of the two front lines, and of 60 men in the triarii. A maniple was commanded by a centurion or captain, who had a second-centurion, or lieutenant, and two sub-officers, or sergeants, under him: as non-commissioned officer there was a decanus, or corporal, to every squad or tent of ten men. The principilus, or senior centurion of the triarii, was the most important regimental officer, and commanded the legion in the absence of the tribunes. The 300 cavalry formed a regiment of ten turme, or troops of 30 horsemen, each under three decurions, of whom the senior had the command. The staff of the legion consisted of six tribunes, who managed the paying, quartering, provisioning, &c. of the troops, and who commanded the legion in turns for a period each of two months. This changing command, although inconvenient, lasted till the times of the civil wars, when a legatus, or lieutenant-general, was appointed as permanent commandant of the legion. In the time of Marius the manipular formation was abolished, the three lines were assimilated, and the legion was divided into 10 cohorts, each of 3 maniples. Soon the cohorts were raised to 600 men, making the legion 6000 infantry, besides cavalry and velites. It was ranged in 2 lines of 5 cohorts each; but Cæsar altered the formation to 3 lines, of respectively 4, 3, and 3 cohorts. During the later empire the legion became complex and unmanageable; many sorts of arms being thrown together, and balistæ, catapults, and onagers added by way of artillery.