History of the East–West Schism
Disunion in the Roman Empire further contributed to disunion in the Church. The Emperor Diocletian famously divided the administration of the eastern and western portions of the Empire in the early 4th century, though subsequent leaders (including Constantine) aspired to and sometimes gained control of both regions. Theodosius the Great, who established Nicene Christianity as the official religion of the Roman Empire (see Edict of Thessalonica), was the last Emperor to rule over a united Roman Empire. Following his death in 395, the division into western and eastern halves, each for a few decades still under its own Emperor, was never reunited.
The Last Legion
The film depicts the coronation of Romulus (and subsequent fall of Rome) as having taken place in 460, while the novel gives the year as 476. In point of fact, coronations were not invented until later in the Roman Empire (in the Byzantine period). Historically, Romulus was a usurper proclaimed by his father in 475. It is believed he was born in 460. Romulus' reign was never recognised as emperor except by his father's troops. The emperors of the East continued to regard Julius Nepos, who had fled Italy and reestablished himself in Dalmatia in the face of a rebellion by Orestes, as the legitimate Western Emperor. Romulus was Emperor for ten months, not a single day as in the film.