Can I ask the question Is religion the cause of wars or is the Medium used by those in power to Support them in a war because of power or wanting land and money and the like, or is that a Philosophy question more then a History questions of course I would want historical case studies proving the point either way?
I would vote to close on the grounds that it is subjective, too broad, and will attract discussion and argumentation. Besides, there are no one true answer to this. Some war were religious in nature, other were not, some were a mix.
Now, if you had a particular ruler and/or war in mind, you could ask something akin to "How motivated by religion was Sauron's war on Gondor in the third age?".