Nero blamed Christians for a fire in Rome and persecuted them, though Constantine later issued the Edict of Milan proclaiming tolerance of Christianity. Constantine became the first Christian emperor, helping Christianity flourish in the Roman Empire. Theodosius the Great then adopted Christianity as the official religion. While Rome's population once reached 50 million, factors in its decline included the rise of Christianity weakening the military, traditional values declining as outsiders gained power, lead poisoning causing mental decline, plague killing many citizens, overreliance on slavery stunting technology, and failures of the political system.

1. Rome & The Rise of Christianity Sections 4 & 5

6. Video “Constantine Becomes Emperor”

8. Video on Rise of Christianity

16. Video: A proud empire collapses