The insolence of the prætorian guard had risen very high during the reign of Commodus; but it had never, even in the time of the Antonines, been entirely suppressed. It was only by large donatives that their consent could be purchased, their caprice satisfied, and their good humour maintained; especially at every new adoption. One of the greatest reproaches to the age of the Antonines is, that those great princes, who seem to have had the means so much in their power, did not free themselves from so annoying a dependence.
Jul. Capitolini Pertinax Imp. in Script. Hist. Aug.
Didias Julianus.
2. When, upon the death of Pertinax, the rich and profligate M. Didius Julianus, aged fifty-seven, had outbid, to the great scandal of the people, all his competitors for the empire, and purchased it of the prætorian guard, an insurrection of the legions, who were better able to create emperors, very naturally followed. But as the army of Illyria proclaimed their general Septimius Severus, Pescennius Niger, Albinus. Septimius Severus, the army of Syria, Pescennius Niger, and the army of Britain, Albinus, nothing less than a series of civil wars could decide who should maintain himself on the throne.
Æl. Spartiani Didius Julianus, in Script. Hist. Aug.
3. Septimius Severus, however, aged 49—66, was the first who got possession of Rome, and, after the execution of Didius Julianus, he was acknowledged by the senate. He dismissed, it is true, the old prætorian guard, but immediately chose, from his own army, one four times more numerous in its stead. And after he had provisionally declared Albinus emperor, he marched his army against Pescennius Niger, already master of the east, whom, after several contests near the Issus, he defeated and slew. Nevertheless, having first taken and destroyed the strong city of Byzantium, a war with Albinus soon followed, whom the perfidious Severus had already attempted to remove by assassination. After a bloody defeat near Lyons, Albinus kills himself, Feb. 19, 197. Albinus kills himself. These civil wars were followed by hostilities against the Parthians, who had taken the part of Pescennius, and which ended with the plundering of their principal cities (see above, p. 304). Severus possessed most of the virtues of a soldier; but the insatiable avarice of his minister Plautianus, the formidable captain of the prætorian guard, robbed the empire even of those advantages which may be enjoyed under a military government, 204. until he was put to death at the instigation of Caracalla. To keep his legions employed, Severus undertook an expedition into Britain, where, after extending the boundaries of the empire, he died at York (Eboracum), leaving his son the maxim, "to enrich the soldiers, and hold the rest for nothing."
Agricola had already erected a line of fortresses, probably between the Firth of Clyde and the Firth of Forth. These were changed by Adrian into a wall along the present boundaries of Scotland. Severus again extended the frontiers, reestablished the fortresses of Agricola, and afterwards built a wall from sea to sea; his son, however, gave up the conquered country, and the wall of Adrian again became the boundary of the empire.
Æl. Spartiani Septimius Severus et Pescennius Niger.
Jul. Capitolini Claudius Albinus, in Script. Hist. Aug.
Caracalla, Feb. 4, 211—April 4, 217.