this post seems to have deteriorated into a slanging match of religion, culture, and perhaps race. not, i think, quite what the op was hoping for.
my own "halfpennyworth" is that war seems to have been a constant for a long time. it's how the rich get richer and ensure they get more than their fair share of "the spoils".
but how do you persuade a lot of sensible people, intent on living/enjoying their lives and feeding their families, to go to war? you use the strongest form of persuader; which has long been religion.
in other words: don't blame the religion for war and the awful things that are done in its name; blame the people who use the religion to their ends.
and note, now that religion is, for many, less of a persuader, there's that much-abused term "democracy". "we" fight (with words as well as guns) for the principle of democracy, and yet in its name our own version of "vote for trump and you get what you deserve" has given away many millions and even billions of pounds to his friends and supporters. whilst allowing the destruction of our home/planet to continue apace.
surely we need a completely new way to make decisions!