The year started with a decisive Roman victory over the Parthians. Their capital Ctesiphon was taken around 28 January after a short siege. The victorious Roman soldiers looted the entire city and took away thousands of women and children as slaves. Herodianus claims the Romans also captured the Parthian king’s treasury.
After his victory at Ctesiphon, Severus decided not to further chase King Vologases. Unfamiliarity with the terrain, an outbreak of diarrhoea among his troops and a lack of provisions forced him to return to Mesopotamia, but not before the soldiers had proclaimed his eldest son Bassianus – who had been renamed Marcus Aurelius Antoninus – Augustus and his youngest son Geta Caesar.
Now Severus focussed on the rich oasis city of Hatra. Hatra had withstood a Roman siege in 117, when the emperor Trajanus had failed to take the city (and had almost died trying). Severus was going to suffer a bloody nose as well. Hatra was a formidable stronghold on a high hill and defended by strong walls. Severus’ first siege of the city started in spring, but failed miserably when the inhabitants of Hatra put up some determined resistance. The weather conditions were terrible and the Romans lost many men to enemy missiles and disease.
In the end, the emperor gave up the siege, only to try taking the city again next year. Severus was not a good loser. He executed his praetorian prefect Julius Crispus and also Laetus, who may have been the same Laetus that saved the day (and probably Severus’ life as well) at Lugdunum the previous year. Apparently, Severus envied and perhaps feared Laetus for his popularity among the soldiers, at least according to Cassius Dio.
– Adrian Goldsworthy, The Fall of the West, p. 67-68.