Wow, what a loaded question.  \n\nThere is a lot of history involved in most of these conflicts.  In other words, it's not just that two groups of people are from different religions.  Just being in those religions does not make a fight (look at America, every faith lives here without fighting).  \n\nInstead the conflicts tend to have socioeconomic (meaning having to do with group interactions and money), and deeply held personal feelings at stake.\n\nLet's look at a hypothetical (b/c I don't want to offend anybody).\n\nA group of people has an uprising because they (correctly) believe that they are being oppressed for monetary gain by another group of people.  We'll call these people the Alphas.  The Alphas belong to religion A.  It takes almost 10 years for the Alphas to overcome their oppressors.  The world looks on and agrees that the fight is good b/c the oppressors are bad.\n\nIn the course of this uprising there are individuals involved who are not good people.  They are not interested in just being free, they want money.  And maybe they want to hurt someone b/c they were always jealous of the stuff that  person had.  Bottom line is that they are not nice (you've met people like this I'm sure).  During the revolution this mean person goes into a section of town occupied by another group of people. We'll call them the Betas.  The Betas belong mostly to religion B.  So the mean person goes into town, and in the name of the revolution takes a bunch of stuff from the Betas.  The Betas don't like this and they fight back, but the mean guy has a whole army so he kills a bunch of Betas (who he doesn't like anyway) and moves on.\n\nSo this mean person goes to the part of town where the Betas live, and steals a bunch of their stuff while the revolution is going on.  Well, unfortunately, sometimes the Betas will see the actions of this one person as indicative of the people who belong to religion A.  Maybe one of the preachers of religion B will have a sermon talking about how mean Alphas can be, which will get the Betas even more upset.\n(I think one of the greatest sins against God and man is to preach a sermon of hate.)\n\nSo now you see the seeds being sown.\n\nWell put another factor on top of this.  If I want people to come together and act like a team, a great way to do this is to give them an enemy.  If people have somewhere to focus their frustration (like if they are hungry, or poor) they can come together, and forget their differences while they attack this perceived enemy. So if I want to bring a group together, and I want to be their leader I'll pick someone they don't like anyway, and I'll tell them everything is their fault.  Let's say that I'm a Beta, and I'm running for Governor.  I don't want anybody to talk about the fact that I'm corrupt and take money from gangsters, so I spend every conversation talking about how the Alphas are really bad people.  That way everyone will agree with me.\n\nSux, huh?\n\nThe only way to get over this stuff is to let the past be.  We must look on for our children.  We must forge peace ourselves.