Wars are fought over treasure, resources, land, religion.
My God is tougher than your God.
What kind of buttface kills someone over disagreements regarding the exact name and teachings of their particular deity?
This is, of course, the main attribute of humanity since recorded time and likely even before that.
Many thousands of years ago, humans and pre-humans apparently fought more over food than over religion, but as soon as some lamebrain invented writing, and we had the ability to record stories regarding killing animals and having sex, we thought it would be a good idea to record stories about our God or Gods.
Immediately we spaced out the part of religion that told us not to kill, and we bent the rule to day we just can't kill those who agree with us.
Everyone else has to be saved, and if they won't let us save them, we have to kill them.
A curious equation:
YOU + MY GOD = LIFE
YOU - MY GOD = DEATH AT MY HANDS
So what the hell are we thinking anyway, as a species? Jesus God, are we idiots?
And actually, it's worse, since it is not only our religion that thinks and acts this way. If we don't convert or kill that guy who doesn't believe what we believe, this is what he thinks:
US + HIS GOD = LIFE FOR US
US - HIS GOD = DEATH AT HIS HANDS
US + OUR GOD = HIM + HIS GOD = DEATH AT EACH OTHERS HANDS