A commenter at the Belmont Club, CatoRenasci, spells out the real nightmare scenario.

"...I honestly believe that to avoid the fight before the Iranians acquire nuclear weapons is to ensure the fight with Islam turns into a Vernichtigungskrieg - a war of extermination."

We need to think about these things very carefully:

"...if Iran reaches the point where they can carry out their President's wish--of wiping Israel off the map--this will lead to a nuclear exchange between Israel and Iran. I would also expect that Israel might engage in the Samson option--figuring that if more than a couple of nuclear weapons go off over Israel, they are not going to continue to exist anymore, they won't need American aid, they already don't much care what a bunch of whining Europeans think, and they might as well exterminate their enemies. That would likely mean destruction of Mecca, Medina, and all major Arab and Iranian population centers for which they have enough bombs."