The crusades back then in Europe were battles over religion and which religion is better almost. So think about it this way, you have two groups like gangs almost one gang says that if you join them they can teach you the truth of the word of god and then the other gang says no to know the truth of the word of god you must do these other things here. then conflict begins between the two and then it turns into great battles fighting to protect each sides religious ideas and truths safe.
