FACT versus Fiction
History and fiction in the film
The plot of The Fall of the Roman Empire' may be called a fantasia on the various historical trends, events, and personages of the years 180-193 C.E., which is seen as the time period in which the Roman Empire ceased to rise and began to decline and, ultimately, fall. Following a plausible interpretation of the historical records, Commodus is depicted as over-compensating for emotional vulnerability and soon descending into instability and corruption. The irony is in Commodus's directive that the empire should "forget the weakness of my father" with its implication that he would be a strong leader: it is Commodus's army of gladiators that proves to be cowards on the field with the German barbarians and Commodus's harsh policy toward the eastern provinces that had the tendency of weakening the empire by the threatened loss of the east. It is his father's true ideological heir, Livius, in contrast to him, who conquers both the Germans and Parthians as well as Commodus himself. In the film Livius is given the epithets "Germanicus" and "Parthius" and is invited to be emperor after the death of Commodus.
The death of Marcus Aurelius is portrayed as the result of a conspiracy to poison him, which was rumoured at the time. Commodus's liking for gladiators and for fighting as a gladiator himself is historically accurate: it led to rumours that he was actually the bastard son of a gladiator who had been the lover of Marcus Aurelius's wife Faustina. The film makes use of this as a subplot in making Commodus's gladiatorial trainer and comrade, Verulus (Anthony Quayle), his real father. This impresses upon Commodus that he is a bastard who never should have been emperor. In a fit of madness he commits patricide by killing Verulus.
Commodus's sister Lucilla's opposition to his rule is also historical: she was even executed for attempting to assassinate him. Her political marriage to the King of Armenia and her survival of her brother are not historically accurate.
The "Battle of the Four Armies" of loyalist and renegade Roman legions against Armenians and Persians is not a historical event. The Sassanid Persian empire did not currently exist at this time (they are standing in for the historical Parthians).
Toward the end of the film Julianus and other senators are shown attempting to bribe the military into making one of them emperor while Commodus and Livius are fighting below them. This makes use of the historical events three months after Commodus's death (he actually died by poisoning and/or strangulation) when Didius Julianus bribed the Praetorian Guard to proclaim him Emperor, outbidding his rival Claudius Pompeianus - a character not shown in the film, though it was he, not a King of Armenia, who actually married Lucilla.
A number of the film's minor characters approximate historical personages: Commodus's corrupt chamberlain Cleander (represented in the film as a blind man), his courtier Niger (who may be identified with Pescennius Niger a rival claimant with Didius Julianus to the imperial throne), and Livius's comrade Victorinus (probably based on the general of the period named Aufidius Victorinus). Other characters of similar political and social standing appear to be completely fictitious.
It is believed that though the film was highly spectacular and considered intelligently scripted, its failure was partly attributable to what was considered the wooden performance of Stephen Boyd as the loyal general Livius (a fictitious character). In contrast, the performance of Christopher Plummer as the unstable Commodus was considered highly charismatic. As a fledgling motion picture performer—The Fall of the Roman Empire was only his third appearance on film—he began to emerge as a major Hollywood star.
The part of Marcus Aurelius was considered to be well portrayed by Alec Guinness, notably in a long soliloquy that was largely quotations from the emperor's own philosophical work The Meditations. The composer Dimitri Tiomkin said he found it impossible to write any music for this soliloquy.
http://en.wikipedia.org/wiki/The_Fall_of_the_Roman_Empire_%28movie%29