It began to spread when Jesus was ministring, although His followers weren't called Christians until much later. Perhaps the biggest single event that caused massive conversions was the day of Pentecost, when 3,000 people turned their lives over to Christ.
Christianity did not easily spread through the Roman Empire. See the related question, "How did Christianity spread throughout the Roman Empire?"
The spread of Christianity had political ramifications for the Roman Empire. The empire split into two, Constantinople to the east and Rome to the west
It could not decline from nothing - it did not exist until after much of what was to become the Roman empire was already under Roman rule. It spread, particularly after the Romans accepted Christianity under Constantine
No religion helped to save Roman culture. One religion spread through the Roman Empire in its later days and transformed Roman culture: Christianity.
Which Roman leader exactly? Whom are your referring to?
Christianity did not easily spread through the Roman Empire. See the related question, "How did Christianity spread throughout the Roman Empire?"
The Roman Empire.
That would be Christianity.
By 325ad Christianity had spread throughout the Roman Empire and to Britain. If you google "spread of Christianity map" you will find maps showing the spread.
Christianity
They used force
The spread of Christianity had political ramifications for the Roman Empire. The empire split into two, Constantinople to the east and Rome to the west
Charlemagne's two main goals were to spread Christianity & to rule the roman empire (:
It could not decline from nothing - it did not exist until after much of what was to become the Roman empire was already under Roman rule. It spread, particularly after the Romans accepted Christianity under Constantine
No religion helped to save Roman culture. One religion spread through the Roman Empire in its later days and transformed Roman culture: Christianity.
Christianity was certainly a constant. Christianity was also spread beyond the area of the former western part of the Roman Empire with the conversion of previously pagan peoples.
The Romans who remained pagans did not contribute to the spread of Christianity Neither did Julian, who was the only pagan emperor in the Later Roman Empire