The smallest tactical unit in the Roman army trusted with independent maneuver was the century, standing 100 man strong (later 80 with the remaining 20 comprising administrative staff and hangers-on). Each century was commanded by a Centurion, a veteran promoted from the ranks after demonstrating bravery, skill, discipline, and leadership. The century was roughly equivalent to the modern infantry platoon and the Centurion was a combination of modern infantry platoon commander (usually a Lieutenant) and top sergeant. Centuries were further organised into cohorts - six centuries per cohort (480 men total) - with the most senior centurion taking overall command of the cohort, akin to a modern infantry company and infantry company commander (usually a Captain or Major). Centurions were the backbone of the legions that built and defended the Roman Empire.