The Byzantine emperor Justinian was born in 482 A.D., just a few years after the fall of the Roman Empire, or technically, for those who view the Byzantine Empire as the continuation of the eastern half of the Roman Empire, just a few years after the fall of the western half of the Roman Empire. In any case, he did not come from a rich aristocratic family, but rather from a poor rural family. He worked his way up the political ladder, finally as an assistant to the emperor Justin. When Justin died, Justinian became emperor.
Justinian had a keen interest in philosophy and religion, and wanted to carefully define words like "trinity" and "incarnation" and supervised the re-building of the Hagia Sophia. His reign was marked by alternating political tensions and friendship between his empire and remnants of the western Roman Empire. These political ups and downs were accompanied by varying emphases on the similarities and dissimilarities between the eastern and western branches of the Christian church. In reality, the belief systems were very similar, but at times of political tensions, attempts were made to make them seem different.
He also did much to popularize the Christian faith, although, at times, he became too enthusiastic and wanted to force people to believe in the new religion. But he never completely illegalized Judaism or paganism, figuring that it is better to persuade people with ideas and not with swords.