Religion has existed since the beginning of time. Religion means a set of beliefs concerning the cause of nature and the purpose of the universe; War means the process of military struggle between two nations or groups of nations, it is characterized by extreme aggression, destruction, and usually a lot of deaths.
Religion does have effects on the warfare practices. The effects may depend on different things. For example, it may depends on the religion(s) that are involved in the conflict. It also may depend the reasons and the beliefs of the religions. Religions can adopt three views of wars. By this I refer it may be the "pacifist view" which is that all violence