Task: Sentence Expansion
Input (English): Successive invasions of Germanic tribes meant the end of the Western Empire in the 5th century , but the Eastern Empire persisted throughout the Middle Ages as the Byzantine Empire .
Output (English): Successive invasions of Germanic tribes finalized the decline of the Western Roman Empire in the 5th century , while the Eastern Roman Empire persisted throughout the Middle Ages , in a state called the Roman Empire by its citizens , and labelled the Byzantine Empire by later historians .