After the Sack of Rome and the Fall of the Western Roman Empire, the Eastern Roman Empire was left. It became known as Byzantium. Justinian’s Uncle was the emperor before Justinian became emperor himself. As his Uncle got older, Justinian began to help him rule, as co-emperor. When his uncle died, he became the sole ruler of Byzantium. Justinian was the last great ruler of the Romans, and ruled over a decent amount of territory. He is also known for Justinian’s Law, a code that combines all of the old Roman laws into one book. In addition to that, he built the Hagia Sophia, a large church.
After Justinian died, his son took over, and Byzantium’s army became too thinly spread to keep out invaders. The borders shrank until the Byzantine Empire was but a small country consisting of Greece and modern-day Turkey.