Here, Gibbon pauses in his narrative to describe the praetorian guard that just assassinated the emperor Pertinax. They were established by Augustus who “had gradually formed this powerful body of guards, in constant readiness to protect his person, to awe the Senate, and either to prevent or to crush the first motions of rebellion” (104). They were given double pay and special privileges, but Augustus kept most of the praetorian guard stationed outside of Rome itself.

Augustus’s successor Tiberius made what Gibbon sees as the fateful decision of permanently stationing the praetorian guard in Rome. The emperors depended on the praetorian guards for their protection, but the praetorian guards were also dangerously powerful and had to be both appeased through high pay, including an extra payment upon the accession of every new emperor, and kept in line through strict military discipline. Over time, the praetorian guards asserted that they too had a say in who a new emperor would be.

Following Pertinax’s assassination, the praetorian guard announced they would make whoever offered them the most money the next emperor. Pertinax’s father-in-law, Sulpicianus, and a wealthy senator named Didius Julianus entered the bidding.