The Praetorian Guard, the bodyguard of the ancient Roman emperors. By the 2d century BC the bodyguard of a Roman general was known as the praetorian cohort, but Augustus, the first Roman emperor, in 27 bc instituted the Praetorian Guard as a separate force by organizing 9 cohorts, each consisting of 1000 men, under the command of a prefect, who was called the praetorian prefect. The only large permanent body of troops allowed in Rome itself, or near the city, it soon acquired great political power. Members served 16 years, receiving special privileges and pay. They gradually began to exercise their political power in an unscrupulous manner, deposing and elevating emperors at their pleasure. In ad 193, after the assassination of Emperor Publius Helvius Pertinax (126-93), they sold the throne to Didius Severus Julianus (133-93). In the same year the Guard was reorganized by his successor, Emperor Lucius Septimius Severus. It was abolished by Emperor Constantine the Great in 312.

Bradbury again has Faber use an allusion while talking to Montag. He is telling Montag that even Caesar had foes and no one can be completely happy and in power. Faber thinks that when they burn books it is showing how stupid they are.
This line is spoken by Faber when he and Montag are talking at his house. The basic idea of the line is that books act to keep us from doing stupid things.
In this passage, Faber is referring to the idea that when Roman emperors had parades, someone supposedly