Commodus (r. 180-192), the true son of Marcus Aurelius, proved to be a tyrant without talent. In the end, his closest advisers murdered him. After two other emperors had been installed and murdered by the Praetorian Guard within a year, Septimus Severus (r. 193-211), a North African who commanded the Roman troops in what is now Hungary, marched his army into Rome and disbanded the guard, replacing it by a new elite body chosen from his own officers.
He emerged successful from the first civil strife Rome had known in more than a century. To reward his armies for their loyalty in a campaign against the Parthians, he provided better food, pay, and allowed his legionaries to marry native women. Married legionaries might live off the base and could keep their own flocks and grow their own crops.
Septimus Severus was succeeded by his two sons, one of whom, Caracalla (r. 211-217), extended citizenship in 212 to all freeborn inhabitants of the Empire. This was a natural climax to the earlier acts gradually expanding the circle of Roman citizens, though it also was a money-raising device, since all new citizens would be liable to inheritance taxes from which noncitizens were exempt.
Caracalla’s successors were all assassinated in their turn. Alexander Severus (r. 222-235) tried to revive cooperation with the Senate and to restore the traditional virtues to Roman life, but he was only fourteen on his accession and was dominated by his mother. The Senate was impotent, and the army resented Alexander’s neglecting the now-traditional bribes. Though his campaign against the new Sassanian dynasty that had replaced the Parthians in Persia was a success (231-233). in Germany on another campaign he fell victim to military conspiracy.
During the half-century (235-284) there were twenty-six emperors, of whom twentv-five were murdered. Most of them were chosen by their troops, held power briefly, and were in turn supplanted by another ambitious military commander. But the army had been weakened by Septimus Severus’s changes, for soldiers had grown accustomed to being used as police, tax collectors, judges, and even artisans, and they often were not ready for combat.
Attracted by Roman weakness and pushed from behind by other people on the move, the so-called barbarians crossed the Roman frontiers at many points. The emperor Decius was killed in battle; the emperor Valerian was captured by the Persians and died in captivity. When the plagues raged, whole provinces temporarily escaped from the central authority, population fell off, public order virtually vanished, and the Empire seemed doomed to collapse. The tide turned with the reign of Aurelian (r. 270-275) and with the accession of Diocletian (r. 284-305). Aurelian drew the best troops back from the frontiers and concentrated on the defense and restoration of Rome. He turned increasingly to non-Roman mercenaries for protection. Diocletian and his successors, especially Constantine (r. 306-337), put through numerous reforms. The result is usually called the New Empire.
Under Diocletian there gradually evolved a system called the tetrarchy (rule by four men). As emperor, Diocletian first appointed a talented officer as Caesar and then was forced by circumstances to promote him to the title of Augustus, or co-emperor, though it was understood that Diocletian was above the other. Each Augustus in turn appointed a Caesar of his own, whom he also adopted as his son. It was understood that the two emperors would eventually abdicate, each to be succeeded by his own Caesar, who upon becoming Augustus would appoint a new Caesar as his son and eventual successor. The scheme was designed to assure a peaceful succession and to end the curse of military seizures of the throne. Thus the Empire, though in practice ruled by four men, still in theory remained a single unit.
This was particularly important, because accompanying the gradual establishment of the tetrarchy was a shift in territorial administration, as each of the four new rulers took primary responsibility for his own large area. Diocletian made his headquarters at Nicomedia in Asia Minor, and from there he governed Asia Minor, Syria, and Egypt, plus Thrace in Europe—the whole becoming the prefecture of the East. From Sirmium in what is now Yugoslavia, his Caesar governed the Balkans, which became the prefecture of Illyricum. From Milano, Diocletian’s co-Augustus, the junior emperor Maximian, governed the prefecture of Italy, which included North Africa together with parts of what is now Austria. And from Trier in the Rhineland, his Caesar governed Gaul, Spain, and Britain, which were grouped into the prefecture of Gaul.
A tough Balkan soldier, Diocletian simply walked out on Rome, leaving the citizens with their free bread and circuses. It is of great importance, too, that he moved his own headquarters to the East, for Diocletian now adopted the full trappings of oriental monarchy. He wore silk robes of blue and gold to symbolize the sky and the sun; he sprinkled his hair with gold dust to create a nimbus when light shone upon him; his clothes glittered with jewels; he wore ruby and emerald bracelets, necklaces, and rings; his fingernails were gilded; and his boots were of purple leather.
He entered his throne room carrying a golden scepter topped with a golden ball or orb—the earth—on which was seated a Roman gold eagle with a sapphire in its beak to symbolize the heavens. Servants followed, sprinkling perfume, which fan bearers spread through the air. Every person in the room sank to the floor until Diocletian was seated on his throne, after which the privileged might kiss the hem of his garment. Diocletian was making a deliberate attempt to elevate the prestige of the emperor—a divine and deified emperor—so high that it could not be shaken by the ambitions of a rival.
Mechanical reorganization and geographical regrouping of forces could not have prevented by themselves the recurrence of military uprisings. Therefore, Diocletian firmly separated the military from the civil power, so that the commanders of local garrisons had no local political authority and his new civil officials had no military authority. Moreover, Diocletian subdivided the old provinces, so that the number of new provinces rose to over one hundred, each much smaller than provinces had formerly been; these in turn were regrouped into twelve so-called dioceses, which constituted the four great prefectures.
Accordingly, the bureaucracy grew enormously. The various financial departments, the secret service, the post, and foreign relations each had its own structure, and the top officials became a kind of advisory body, almost a cabinet. Diocletian also enlarged the army, which probably reached a new high of about 600,000. He reorganized the forces and improved their pay and promotion system.
The new bureaucratic and military costs required new contributions from most of the population. By using as a unit for tax purposes the amount of land that could be cultivated by a single farm laborer, and by trying to force the farm laborer to stay put, work his land, and pay his taxes, the New Empire greatly stimulated the growth of that class of rural resident called the colonus (plural, coloni). The colonus was not a slave and could not be sold apart from the land he and his family cultivated, but when it was sold, the coloni went with it. Other men in other walks of life were also bound to their jobs, and sons to their fathers’ jobs after them.
The lowest territorial administrative level was the civitas (a city and its surrounding countryside). The city senators (curiales) had to make up out of their own pockpockets any difference between the tax payments assessed for the civitas and the amount actually collected. Society became more rigidly stratified than ever before in Roman history. The combination of this increased social stratification with oriental-style despotism, a huge bureaucracy, and continuing dependence on the military made life extremely bleak for the ordinary person. Corruption, inequity, violence, and despair were frequent. The tax collector became the symbol, not of the stability of the state, but of corruption and greed.
Diocletian retired in 305 and left his half of the Empire to his Caesar; he forced his fellow Augustus, Maximian, to do the same. Each of the new Augusti in turn named a new Caesar; but the system broke down as the four top officials began to struggle against one another for supreme power. By 324 Constantine, son of the Western Caesar, emerged as sole Augustus, and the Empire was reunited; he ruled until 337.