Ultimate victory over rivals Pescennius Niger and Clodius Albinus allowed Septimius Severus to focus his attention addressing legionary reform and engaging in military endeavors against external threats. Having already reformed the praetorian guard, who were responsible for the murder of Pertinax and the auction of the empire to Didius Julianus, Severus raised the pay scale by one half of the standard for legionaries, allowed more opportunities for promotion and in AD 197 legalized marriage for soldiers.
While soldiers had certainly long maintained unrecognized marriage, this step brought the rights of legionaries in line with those of other citizens and allowed the children of such marriages to be legally recognized as citizens. While pay raises and benefits along with the increased citizen roles was certainly expensive, such steps allowed for a greater recruiting base, and supported Severus’ values on the importance of family. Thusly, the emperor who had been a career soldier not only showed his appreciation for the military that helped him to the throne, but presumably expected these rewarding measures to increase loyalty and morale.
The emperor would quickly put his legions to the test. In AD 197, earlier attempts by the Parthian King Vologases V during the Roman civil war to reassert control over Mesopatamia destabilized the eastern frontier and eventually culminated in another war with Rome’s old rival Parthia. Severus marched east after raising three new legions, I, II and III Parthica, one of which (II Parthica) would eventually be stationed as a permanent garrison in Italy on the Alban Mountain for both internal control and as a centralized reserve. Parthian resistance was minimal and the Romans swept down the Euphrates on the same path set by Trajan nearly a century earlier sacking Seleucia, Babylon and the Parthian capital Ctesiphon.
Also much like Trajan, Severus failed at Hatra and ultimately was unable to fully annex Mesopatamia, but was wildly successful in the gathering of spoils in the form of immense monetary wealth and untold slaves. Severus took the title Parthicus Maximus in honor of the victory, and though the Roman grip on the far eastern provinces would remain tenuous at best, Parthia was crippled as a result of the Severan war. By AD 224, the Parthian kings would fall and be supplanted by the Sasanian Persian Empire.
Severus returned to Rome in AD 202 after an extensive tour of the eastern provinces. Included in his court was the Praetorian Prefect Gaius Fulvius Plautianus, who had been appointed just prior to the Parthian campaign. Plautianus had a reputation for imperial influence and viciousness that rivaled the memory of Tiberius’ Prefect Sejanus. Cassius Dio records: “Plautianus, who not only shared Severus' power but also had the authority of prefect, and possessed the widest and greatest influence of all men, put to death many prominent men among his peers… He wanted everything, asked everything from everybody, and would take everything. He left no province and no city unplundered, but snatched and gathered in everything from all sides; and everybody sent a great deal more to him than to Severus… At home he castrated a hundred Roman citizens of noble birth, though none of us knew of it until after he was dead. From this anyone may comprehend the full extent both of his lawlessness and of his power.” The power of Plautianus was such that contemporaries described him as having more power than that of the three (Severus and his two sons). His prominent position was confirmed though adlection into the Senate, appointment as consul and the marriage of his daughter Plautilla to Severus’ son Caracalla.
The imperial family had much to celebrate upon it’s return to the capital: an earlier promotion of Caracalla to co-Augustus and Geta to Caesar in AD 198, the wedding of Caracalla and the victories of Severus against Parthia. As such, in AD 202 Rome celebrated the decennalia games marking the tenth year of the reign of Severus. The entire family next traveled to Severus’ familial home of Lepcis Magna and the celebration of Africa’s favored son continued while Severus enriched the city with monuments. In AD 204, the family again returned to Rome and the revelry finally culminated in the grandiose Secular Games, and the dedication of Severus’ triumphal arch in the forum. However, the celebration of Plautianus would not continue much beyond the end of the year.
By the end of 204 Plautianus was the source of terrible friction within the imperial family. Severus’ wife Julia Domna and his brother Geta despised the prefect and the marriage between Caracalla and Plautina was not a happy one. A plot to kill Severus was exposed by a centurion (though the affair was likely an invention of Caracalla and perhaps included broader involvement of the entire family) and Plautianus was summarily executed. As a result, Caracalla was divorced and the entire court less subject to the instigations of the prying prefect. Plautianus was to be replaced by a much more moderate pair of administrators including the renowned jurist Papinian. In fact Severus reign was one in which the law and the value of the court system was a key component. Despite the relative position of Severus as a tyrant in the eyes of the traditional senatorial aristocracy, the Roman courts functioned with fairness and efficiency. His reliance upon such famed lawyers as Paul and Ulpian as well as the afore-mentioned Papinian led to a prominent period of Roman jurisprudence.
Unfortunately, the absence of the controlling Plautianus may have helped foster a growing sibling rivalry between the two sons of Severus along with the sort of deviant behavior that might be expected from the teenaged sons of the emperor of Rome. Severus, seems to have suspected that a change of environment and increased responsibility may help quell the difficulties between Rome’s future leaders, and focused his attention on the troublesome barbarians north of Hadrian’s Wall in Britannia. Herodian suggested that “they (Caracalla and Geta) could return to their senses, leading a sober military life away from the luxurious delicacies of Rome."
Herodian described the situation in Britain in AD 207 as, "The barbarians of the province were in a state of rebellion, laying waste the countryside, carrying off plunder and wrecking almost everything." Conventional wisdom would suggest that at least a portion frontier unrest can be attributed to the civil war between Albinus and Severus which temporarily stripped the province of it’s legionary presence (though clearly the province was not completely abandoned of it’s large auxiliary forces and legionary losses were eventually replaced.)
Whatever Severus’ ultimate motivation; the welfare of his sons, the restoration of Rome’s northernmost frontier or his own inclination towards military adventure, the imperial family arrived in Britain in 208. Roman advances were initially successful in clearing Caledonia of resistance, but as with all other Roman campaigns north of Hadrian’s Wall, any permanent resolution was fleeting. Severe gout and deteriorating health had limited Severus’ ability to personally campaign, and Roman gains were limited. Despite a temporary restoration of the frontier at the Antonine Wall, it would not be long before the border was returned to an improved and stone fortified Hadrian’s Wall.
In February of AD 211, after a reign of 18 years, Septimius Severus died at Eboracum (York) leaving his quarrelsome sons to destabilize all that he had accomplished. According to Cassius Dio, Severus left his sons three pieces of advice, “be harmonius, enrich the soldiers, and scorn all other men.” The second two were well heeded, but the first was completely ignored and Geta would not live to see the end of the year. Severus’ ashes were interred in the Mausoleum of Hadrian and shortly thereafter, despite a strained relationship with some elements of the traditional aristocracy, he was deified by the senate.