I think it better to keep a profound silence with regard to the Christian fables, which are canonized by their antiquity and the credulity of absurd and insipid people.
In most cases, obviously, soldiers fought because a government drafted them and gave them a rifle. At every point too, we see the role of nationalistic sentiment, commercial rivalries, and simple greed. But can we ever separate out such motives from the religious? Was that not also true of the medieval crusades?