Carus, who was elected in his place, maintained the reputation of the Roman arms in the East; but his supposed death by lightning, by delivering the sceptre into the hands of his sons Carinus and Numerian (December 25, 283), once more placed the Roman world at the mercy of profligacy and licentiousness.  A year later, the election of the Emperor Diocletian (September 17, 284) founded a new era in the history and fortunes of the empire.

It was the artful policy of Diocletian to destroy the last vestiges of the ancient constitution.  Dividing his unwieldly power among three other associates—­Maximian, a rough, brutal soldier, who ranked as Augustus; and Galerius and Constantius, who bore the inferior titles of Caesar—­the emperor removed the centre of government by gradual steps from Rome.  Diocletian and Maximian held their courts in the provinces, and the authority of the senators was destroyed by spoliation and death.

VI.—­Reign of the Six Emperors

For twenty-one years Diocletian held sway, establishing, with the assistance of his associates, the might of the Roman arms in Britain, Africa, Egypt, and Persia; and then, on May 1, 305, in a spacious plain in the neighborhood of Nicomedia, divested himself of the purple and abdicated the throne.  On the same day at Milan, Maximian reluctantly made his resignation of the imperial dignity.

According to the rules of the new constitution, Constantius and Galerius assumed the title of Augustus, and nominated Maximin and Severus as Caesars.  The elaborate machinery devised by Diocletian at once broke down.  Galerius, who was supported by Severus, intrigued for the possession of the whole Roman world.  Constantine, the son of Constantius, on account of his popularity with the army and the people, excited his suspicion, and only the flight of Constantine saved him from death.  He made his way to Gaul, and, after taking part in a campaign with his father against the Caledonians, received the title of Augustus in the imperial palace at York on the death of Constantius.

Civil war once more raged.  Maxentius, the son of Maximian, was declared Emperor of Rome, and, with the assistance of his father, who broke from his retirement, defended his title against Severus, who was taken prisoner at Ravenna and executed at Rome in February 307.  Galerius, who had raised Licinius to fill the post vacated by the death of Severus, invaded Italy to reestablish his authority, but, after threatening Rome, was compelled to retire.

There were now six emperors.  Maximian and his son Maxentius and Constantine in the West; in the East, Gelerius, Maximin, and Licinius.  The second resignation of Maximian, and his renewed attempt to seize the imperial power by seducing the soldiers of Constantine, and his subsequent execution at Marseilles in February 310, reduced the number to five.  Galerius died of a lingering disorder in the following year, and the civil war that broke out between Maxentius and Constantine, culminating in a battle near Rome in 312, placed the sceptre of the West in the hands of the son of Constantius.  In the East, the alliance between Licinius and Maximin dissolved into discord, and the defeat of the latter on April 30, 313, ended in his death three or four months later.