Gladiators were condemned criminals, prisoners of war, or slaves bought for the purpose of gladiatorial combat by a lanista, or owner of gladiators. Professional gladiators were free men who volunteered to participate in the games. Roman crowds preferred combat by free men over that of slaves. For example, the character of Echion is excited about games in which free men, "not a slave in the batch," will fight. Though low on the social scale, free men often found popularity and patronage of wealthy Roman citizens by becoming gladiators. The emperor Augustus sought to preserve the pietas and virtus of the knight class and Roman senate by forbidding them to participate in gladiatorial combat. Later, Caligula and Nero would order both groups to participate in the games. Romans citizens legally derogated as infamus sold themselves to lanistae and were known as auctorati. Their social status was neither that of volunteers nor condemned criminals, or slaves. Condemned criminals, the damnati ad mortem who committed a capital crime, entered the gladiatorial arena weaponless. Those criminals who did not commit a capital crime were trained in private gladiator schools, ludi. At these private and schools, gladiators had become specialists in combat techniques that disabled and captured their opponents rather than killed them quickly. Criminals trained in gladiator schools fought with the weapons and armor of their choice and could earn their own rights if they survived three to five years of combat. Though a gladiator was only required to fight two or three times a year, very few survived the three to five years. As a gladiator, a man gained immediate status. Gladiators were required to do what their lanista ordered and therefore were revered for their loyalty, courage and discipline