More wars have been fought, and more people have been killed, by religious differences than for any other reason.
This is a myth, unless you consider communism/socialism a religion(which I do).
Hitler, Stalin, Mao, Pol Pot, Chavez, etc. butchered and starved far more people than have died in wars of religious origin, particularly Christianity originated.
If small religious wars were to be counted, one would have to count tribal wars(mostly non-religious), as well. There were probably more wars in New Zealand in the relatively short time frame of its human occupation than there have been "religous" wars world wide.
That being said, humans with a thirst for power will use any means necessary to gain that power. Religion is one of the more powerful motivators. But its use in that manner is a human thing, not unlike the yearning for socialism.
Christianity(the teaching of Jesus, not the worship of the old testament) clearly does not teach that war is a means to the end. Many others(old testament beliefs, islam, Shintoism, etc) clearly proffer it as a means to their final acceptance.