He was the winner of the Year of the Five Emperors

One of the interesting facts about Septimius Severus is that he was the winner of the Year of the Five Emperors. Pertinax, Didius Julianus, Pescennius Niger, Clodius Albinus, and Septimius Severus were the five Roman emperors during the Year of the Five Emperors in AD 193. This year saw the beginning of a period of civil strife in which various rulers vied for the position of Caesar.

The political upheaval began on New Year's Eve 192, with the assassination of Emperor Commodus. After Commodus was slain, Pertinax was appointed Emperor, but his attempts to institute reforms sparked opposition in the Praetorian Guard. They then plotted his murder, and Pertinax was assassinated while attempting to reason with the mutineers. He had barely reigned for three months. Didius Julianus succeeded Pertinax after purchasing the title from the Praetorian Guard, but was deposed by Septimius Severus and executed on June 1. The Senate declared Severus Caesar, but Pescennius Niger was hostile when he declared himself Emperor. This sparked a civil war between Niger and Severus, with both gathering soldiers and fighting across the empire's borders. Because of the conflict, Severus appointed Clodius Albinus as co-Caesar, whom he feared being a threat so that Severus would not have to worry about imperial governance. This decision freed him up to focus on the struggle against Niger. Most historians consider Severus and Albinus to be two emperors, despite the fact that they reigned concurrently. The Severan dynasty arose from the chaos of AD 193.