Corrected entry: Aetius was in real life a very respected general, not a scheming opportunist who regains his lost reputation through questionable means.
Corrected entry: Trebuchets were not invented until at least the 8th century (most references say 12th or 13th). Some of Attila's "catapults," however, are small trebuchets.
Correction: Trebuchets were presumably invented in China between the 5th and 3rd century BC. Attila is reported to have used them when he succesfully besieged (and thereafter sacked) Naissus (present day Nis).
Corrected entry: Valentinian's sister, Honoria, was actually a sheltered woman in real life. She was never a loose woman as depicted in the film.
Correction: This is not true. Honoria was indeed devoted to virginity at the orders of her brother, but this was a situation she did not find to her liking to put it mildly. Around 449 AD, she was apprehended in a love affair with the overseer of her estates. It was presumed that both were engaged in a plot to seize power for Honoria. The overseer was executed and Honoria was exiled to Constantinople. All these events are depicted quite accurately in the movie.
Correction: It's a fact Aetius supported the usurper Johannes against Placidia, the baby Valentinian and Theodosius in 423. When Johannes was executed, Aetius used his army of mercenary Huns to become comes (count) of Gaul. In 432 Placidia fired him, after which he fled back to the Huns and their king Ruga, who provided him with an army. With this army he regained his position, personnally killing his rival Bonifatius in a duel. So I think the movie is quite accurate in pointing out Aetius had a darker side to him.