The middle east wars - religion/power/creed
Prior to modern day, war would have really began due to survival. As tribes grew, space and resources ran out, who got the food? Who got the fresh water? etc.
Then there became nations, large tribes and protecting if they had resources or taking from another if they ran out.
Then greed and power from kings, if all was well, they wanted more. Or to further secure and expand by conquering and making survivors allies so no longer a threat.
Then religions, ones like some islam ones that teach to conquer non believers or kill those who leave the faith.
Nationalism - Hitler - remove non natives from the country, keep pure blood. This type may resurface with mass immigration into Europe. Those on certain race/ethnicities being breed out of existence, etc.
In the end many reasons for wars.