In this book I'm making, there is a religious conflict that happens. Here's the base of my plot so far:
Adrian lives in the dragon tribe Sa'fwan. Foreigners came to his land, coming across his tribe first. They befriended him and his tribe. One particular foreigner, an 18 or 20 year old by the name of Gallan, becomes close friends with Adrian. Adrian later casually reveals that He and other members of his tribe (and other tribes on his land) don't believe in any gods. They just believe that things happen, and everyone just exists, then doesn't exist. Gallan is surprised and tells Adrian that where he's from, many believe in gods. Adrian mentioned it because Gallan was wondering what gods Adrian and his fellow tribefolk believed in. This ends up driving their friendship apart, as Gallan and his fellow foreigners try to convert the tribefolk. This ends up in a war.
Now, I'm not going to spoil much, and I am still in the early stages.
So how do I portray a religious conflict?
Edit: Some people have asked questions, so I'll answer each:
I have only done some research on previous conflict. I know that disease can cause of the death of one side more often, but what usually gave people the upper hand was technological advancements such as the steam engine and the Maxine Machine Gun for one part of history that I learned. (forgot which conflict) This conflict will be different (not that much) due to the fact that it is over religion and non-belief.
The conflict is because Adrian and his tribefolk don't believe in any gods. Gallan and his fellow foreigners see this as a bad thing and want to "save them". I will also include other things that atheists, agnostics, and other non-believers have to often face (and I know a lot, being an atheist). Miracles do not exist. The foreigners believe in the gods, and even manage to convert a few of the willing tribefolk. Not that much, but they do convince some.
I'm struggling with how I should specifically portray the religious conflict. How should the foreigners treat the tribefolk before and after? Should there be battles? What else?