On 28 March 193, Pertinax was at his palace when a contingent of some three hundred soldiers of the Praetorian Guard rushed the gates (two hundred according to Cassius Dio). Sources suggest that they had received only half their promised pay. Neither the guards on duty nor the palace officials chose to resist them. Pertinax sent Laetus to meet them, but he chose to side with the insurgents instead and deserted the emperor.
After the murder of Pertinax on 28 March 193, the Praetorian guard announced that the throne was to be sold to the man who would pay the highest price. Titus Flavius Claudius Sulpicianus, prefect of Rome and Pertinax's father-in-law, who was in the Praetorian camp ostensibly to calm the troops, began making offers for the throne. Meanwhile, Julianus also arrived at the camp, and since his entrance was barred, shouted out offers to the guard. After hours of bidding, Sulpicianus promised 20,000 sesterces to every soldier; Julianus, fearing that Sulpicianus would gain the throne, then offered 25,000. The guards closed with the offer of Julianus, threw open the gates, and proclaimed him emperor. Threatened by the military, the senate also declared him emperor. His wife and his daughter both received the title Augusta.
Because Julianus bought his position rather than acquiring it conventionally through succession or conquest, he was a deeply unpopular emperor. When Julianus appeared in public, he frequently was greeted with groans and shouts of "robber and parricide." Once, a mob even obstructed his progress to the Capitol by pelting him with large stones.
Proclaimed emperor in 193 by his legionaries in Noricum during the political unrest that followed the death of Commodus, he secured sole rule over the empire in 197 after defeating his last rival, Clodius Albinus, at the Battle of Lugdunum. In securing his position as emperor, he founded the Severan dynasty.