This is a random, off-the-cuff observation. I don't have data to support it.
It is my belief that civil wars are most explosive in regions where there is a 45%-40%-15% composition of three factions, especially when the 15% is in the position to be the gate-keeper for some key resource.
The 15% can play the two sides against each other. The dynamics become wildly unpredictable. Ultimately, the 15% is the biggest loser as the two near-majorities have long memories.