"More people have been killed in the name of God than any other reason"

People try to work religion into almost everything. Genghis Khan conquest and killings had nothing to do with religion, neither did Pol Pot in Cambodia. For the non-religious it is an easy saying to believe, mainly because that is what they want to believe. Neither WWI or WWII had anything to do with religion. The Roman conquest, no. Alexander the Great conquests, no again. The Spanish conquest of the Americas was more about gold than religion although they sent their friars along with their forces. Greed, land, resources and believing the people you are about to fight are inferior are at the top for the reasons of war.