Question: how did the middle ages change the world

title: Middle Ages
text: As Western Europe witnessed the formation of new kingdoms , the Eastern Roman Empire remained intact and experienced an economic revival that lasted into the early 7th century . There were fewer invasions of the eastern section of the empire ; most occurred in the Balkans . Peace with the Sasanian Empire , the traditional enemy of Rome , lasted throughout most of the 5th century . The Eastern Empire was marked by closer relations between the political state and Christian Church , with doctrinal matters assuming an importance in Eastern politics that they did not have in Western Europe . Legal developments included the codification of Roman law ; the first effort -- the Codex Theodosianus -- was completed in 438 . Under Emperor Justinian ( r . 527 -- 565 ) , another compilation took place -- the Corpus Juris Civilis . Justinian also oversaw the construction of the Hagia Sophia in Constantinople and the reconquest of North Africa from the Vandals and Italy from the Ostrogoths , under Belisarius ( d . 565 ) . The conquest of Italy was not complete , as a deadly outbreak of plague in 542 led to the rest of Justinian 's reign concentrating on defensive measures rather than further conquests .