Like his predecessors, he was aroused to the wildest ferocity by fear of assassination. His aunt Lucilla formed a conspiracy to kill him; he discovered it, had her executed, and on proof or suspicion of participation put so many men of rank to death that soon hardly any survived who had been prominent in Marcus’ reign. Delators, who had almost disappeared for a century, returned to activity and favor, and a new terror raged in Rome. Appointing Perennis as praetorian prefect, Commodus yielded the reins of government to him, and (the tradition says) abandoned himself to sexual dissipation. Perennis ruled efficiently but mercilessly; he organized his own terror and had all his opponents slain. The Emperor, suspecting that Perennis planned to replace him, surrendered this second Sejanus to the Senate, which reenacted its role of glowing revenge. Cleander, a former slave, succeeded Perennis (185) and surpassed him in corruption and cruelty; any office might be had for a proper bribe, any decision of any court could be reversed. Under his orders senators and knights were put to death for treason or criticism. In 190 a mob besieged the villa where Commodus was staying and demanded Cleander’s death. The Emperor accommodated them. Cleander’s successor, Lactus, after holding power for three years, judged that his time had come. One day he chanced upon a proscription list that contained the names of his supporters and friends, and of Marcia. On the last day of 192 Marcia gave Commodus a cup of poison; and when it worked too slowly the athlete whom he had kept to wrestle with strangled him in his bath. He was a youth of thirty-one.
When Marcus died Rome had reached the apex of her curve and was already touched with decay. Her boundaries had been extended beyond the Danube, into Scotland and the Sahara, into the Caucasus and Russia, and to the gates of Parthia. She had accomplished for that confusion of peoples and faiths a unity not of language and culture, but at least of economy and law. She had woven it into a majestic commonwealth, within which the exchange of goods moved in unprecedented plenty and freedom; and for two centuries she had guarded the great realm from barbarian inroads and had given it security and peace. All the white man’s world looked to her as the center of the universe, the omnipotent and eternal city. Never had there been such wealth, such splendor, or such power. Nevertheless, amid the prosperity that made Rome brilliant in this second century, all the seeds were germinating of the crisis that would ruin Italy in the third. Marcus had contributed heavily to the debacle by naming Commodus his heir and by wars that centralized ever more authority in the hands of the Emperor. Commodus kept in peace the prerogatives assumed by Aurelius in war. Private and local independence, initiative, and pride withered as the power and functions of the state increased; and the wealth of nations was drained away by ever-rising taxation to support a self-multiplying bureaucracy and the endless offensives of defense. The mineral wealth of Italy was diminishing, pestilence and famine had taken bitter toll, the system of tillage by slaves was failing, governmental expenditures and doles had exhausted the Treasury and debased the currency. Italian industry was losing its markets in the provinces through provincial competition, and no economic statesmanship appeared to make up for a languishing foreign trade by a wider distribution of buying power at home. Meanwhile the provinces had recovered from the exactions of Sulla, Pompey, Caesar, Cassius, Brutus, and Antony; their ancient skills had revived, their industries were flourishing, their new wealth was financing science, philosophy, and art. Their sons replenished the legions, their generals led them; soon their armies would hold Italy at their mercy and make their generals emperors. The process of conquest was finished and was to be reversed; henceforth the conquered would absorb the conquerors.