My father (and other world history buffs) can go into much better detail than I can. The conflicts in the Middle East (and ties) go back literally thousands of years. There are not only conflicting religous claims, but also numerous political histoies for virtually every grain of sand in the region. A comprehensive matrix of them would literally run in about 4 or 5 directions, and most folks think they are all valid. It is a quagmire.

That being said, the official foreign policy/religous belief of Iran is that a new Caliphate will arise (of course headed by Iran) and when it does the direct decendant of Mohammad will reveal himself to lead it (and of course he will be an Iranian). In the process all those blasphemous Sunni muslims, Jews, and Cristians will be dead or converted (I guess the Bhuddists and hindi get a pass for now), what happens to the atheists is much uglier. Step 1 has always been the elimination of Iraq. Once that happens they probably assume that Syria will join them as they are shia also. At this point the Med opens up the rest of the world to them.

Is all this practical, probably not, but when has religous/cultural belief EVER been practical? It is ordained.