Still in Syria, Severus decided to cross the Euphrates during the summer months for a punitive expedition into Mesopotomia against the people of Osrhoene and Adiabene. They had revolted against Niger’s forces holding Nisibis – a Roman strongpoint since the campaigns of Lucius Verus – and had killed or captured most of the Roman soldiers. The circumstances were difficult, the summer heat was terrible and there was a serious lack of drinking water, but Severus’ campaign was a success. He managed to retake Nisibis and had his generals Candidus and Laetus ravaged the countryside. He left a member of the equestrian order in charge of the city and claimed he had won an important victory. Not everyone agreed. Cassius Dio lamented that Nisibis “yields very little and uses up vast sums” and complained that it was “responsible for our constant wars as well as for great expenditures”. The historian had a point here.
Back to the West
Severus now expected trouble from his remaining rival for the throne, Clodius Albinus, governor of Britannia, whom he had named his Caesar in 193. Albinus had crossed the Channel and was now in Gaul. As Caesar, he had nominal control of the Spanish and Gallic provinces. Severus suspected Albinus of having secret contacts with several influential Roman senators, who would rather have a scion of an important noble Roman family like the gens Clodia on the throne than an upstart from Africa like Severus. Civil war was looming again and Severus hurried back to the West from Mesopotamia.
Severus now took several important decisions. He named his seven-year-old son Lucius Septimius Bassianus (who would later become the emperor Caracalla) his Caesar. Obviously, this was a blow in the face for Albinus and a further sign that war between Severus and Albinus was imminent. Herodianus claims that Severus also tried to have his opponent assassinated. For this he employed some of the Imperial couriers. These received orders to approach Albinus and tell him that they had secret messages for him, which they could only present to him in private. Then they were to kill him. Herodianus also claims they were to bribe some of the kitchen staff and provide them with poison, which they were to put in Albinus’ food. Wary of assassination attempts, Albinus surrounded himself with a large bodyguard. When the couriers arrived, the plot was revealed, and Albinus had the couriers tortured. They confessed their plans and were subsequently executed. Now, probably in November or December, Albinus began to prepare for war.
– Adrian Goldsworthy, The Fall of the West, p. 65.