During the second century, when there was only one fort, a single tribune headed the horse guard. In the third century, after Septimius Severus built the New Fort and raised the strength of the horse guard from 1000 to 2000 men, two tribunes held the command, one over each fort. Their tasks were to look after the discipline, equipment, and training of their troops, and to lead them in the capital as well as in the field.