Further down the slippery slope

What causes internal ethnic or politic strife of whatever intensity to turn into a full fledged, bloody and ultimately self-destructive civil war? Often it takes just one triggering event; an event that in the grand scheme of things may seem relatively minor. I am not suggesting that the rape of 20 year old Iraqi woman is a minor event but I am thinking that it could prove to be just such a trigger.

I hope that I am wrong.