History of the Roman Empire
Theodosius was the last Emperor who ruled over the whole Empire. After his death in 395, he gave the two halves of the Empire to his two sons Arcadius and Honorius; Arcadius became ruler in the East, with his capital in Constantinople, and Honorius became ruler in the West, with his capital in Milan and later Ravenna. The Roman state would continue to have two different emperors with different seats of power throughout the 5th century, though the Eastern Romans considered themselves to be the only ones who were fully Roman. Latin was used in official writings as much as, if not more than, Greek and the two halves were nominally, culturally and historically, if not politically, the same state.
History of the Roman Empire
The Western Roman Empire began to disintegrate in the early 5th century as Germanic migrations and invasions overwhelmed the capacity of the Empire to assimilate the migrants and fight off the invaders. The Romans were successful in fighting off all invaders, most famously Attila the Hun, though the Empire had assimilated so many Germanic peoples of dubious loyalty to Rome that the Empire started to dismember itself. Most chronologies place the end of the Western Roman empire in 476, when Romulus Augustulus was forced to abdicate to the Germanic warlord Odoacer. By placing himself under the rule of the Eastern Emperor, rather than naming himself Emperor as other Germanic chiefs had done, Odoacer ended the Western Empire by ending the line of Western Emperors. The eastern Empire exercised diminishing control over the west over the course of the next century. The empire in the East—known today as the Byzantine Empire, but referred to in its time as the "Roman Empire" or by various other names—ended in 1453 with the death of Constantine XI and the fall of Constantinople to the Ottoman Turks.