While having a conversation on the subject of conversion to different religions through history one person was adamant that Christianity spread almost entirely through diplomacy and willing conversions unlike "other" religions. I am sceptical about this, since we don't see pagan communities (Ancient Greek, Roman, Egyptian pantheons etc) around anymore. I argue that this was because they were given the choice to convert or die, while he is adamant that this is not the case.
All the stories I've read from that time (Azazeel) support my case and speak of a lot of persecution and violence done by Christians to pagans. But I would like actual credible and scientific sources. Am I right? Is my friend? I suspect the truth may be somewhere in the middle, if so, what is the proportion of the two? My mind is open.
EDIT: Grammar
Well, this is a complicated question and Christianity itself was something of a "house divided" in Antiquity due to differing interpretations of the Gospel and different sects emerging, not to mention that conversion to Christianity was an ebb and flow played over centuries as opposed to a single sweeping force.
Early Islam is also not my forte but if by "other religions" he means polytheistic cults, that is just not true: /u/Tiako answered "What did religion mean to the Common Man in Ancient Egypt? "
/u/AnUS-27 answered an older question that gets into syncretisation of foreign deities
/u/BaffledPlato answered whether or not polytheists believed that some religions were "false"
Did ancient polytheistic religions view themselves as mutually exclusive to one another?
When and how did the religion of the Ancient Egyptians die out?
I do not know that much about early Christianity but there are some people around these parts that do so here are some links to answers that I found to be helpful.
/u/Talondearg and /u/Tiako answered How did Christianity go from a small hated cult to the state religion of the Roman Empire? and /u/Tiako returns with How aggressive was the spread of Christianity in Europe?
/u/Tolboe and /u/thejukeboxhero chimed in on why did Christianity explode in popularity so fast?
A thread with some good reading recommendations as well as some discussion
/u/shlin57 did a nice job of going over how Christianity overcame paganism before talking about How important was the conversion of the Roman Empire to the spread of Christianity? Would Christianity have been remotely as widespread if it wasn't for Constantine?
/u/jasoncaspian talked about whether the conversion of the Roman Empire to Christianity was met with popular resistance
/u/alriclofgar talks about What was the transition to Christianity like in Britain? How long did paganism persist, and what was the nature of the early missionaries?
This thread on religious tolerance in the Roman Empire
/u/elev57 answered Did the treatment of Jews living in the Roman Empire worsen as Christianity became the dominant religion?
But even these do not fully encompass the scope of your question so hopefully someone who knows about this can jump in (maybe some mods with appropriate flair will see this).