I predict if he rides in an a horse against today's military weaponry, he's in for a severe ass whuppin'.
About the only thing he will be able to do is take all his minions to paradise.
Besides, the so-called "Twelvers" are nuts. Everybody knows that the "Seventh Imam" is the true Mahdi.
He may indeed take the islamic nations to paradise - the one with the 72 virgins. If that happens, we should name a national holiday after him.