The former, rising by degrees from the most humble condition, were invested with the civil and military administration of the Roman world.

From the reign of Severus to that of Diocletian, the guards and the palace, the laws and the finances, the armies and the provinces, were intrusted to their superintending care; and, like the Viziers of the East, they held with one hand the seal, and with the other the standard, of the empire.

The ambition of the praefects, always formidable, and sometimes fatal to the masters whom they served, was supported by the strength of the Praetorian bands; but after those haughty troops had been weakened by Diocletian, and finally suppressed by Constantine, the praefects, who survived their fall, were reduced without difficulty to the station of useful and obedient ministers.

When they were no longer responsible for the safety of the emperor's person, they resigned the jurisdiction which they had hitherto claimed and exercised over all the departments of the palace.

They were deprived by Constantine of all military command, as soon as they had ceased to lead into the field, under their immediate orders, the flower of the Roman troops; and at length, by a singular revolution, the captains of the guards were transformed into the civil magistrates of the provinces.