All Aboard the Middle East Nuclear Arms Race
I'll add three things we've discussed here before, but never all at the same time.
• When the Saudis fronted Pakistan money and manpower for the first "Islamic nuke," it wasn't out of Islamic solidarity -- it was with a wary eye on Iran, because historically the Persians usually make better fighters than the Arabs do. Also Saudi's oil-rich Eastern Province is dominated by Iran's Shi'a brothers, and not by the Kingdom's majority Sunnis. Riyadh's other eye, equally wary, was on the United States. The House of Saud needed plausible deniability that Islamabad's nuclear program was in part actually their nuclear program, so as not to unduly upset their guarantors. Also, you never know with those feckless Americans -- best to have some nukes on call. (This last point seems especially pointy in recent years.)
• Unless we're willing to bring the Arab Middle East under our nuclear umbrella, an Iranian nuke means a Saudi nuke, and probably also a Turkish nuke. Yes, the Turks already are under our umbrella -- but what a wonderful excuse to finally get one all their own. At that point even Egypt might be sorely tempted.
• And this last item ties together nicely with the first two. Any reasonably technically competent country which really wants nukes, will get nukes. Short of war, there's no way to stop them if they're willing to endure some hardships.
I'll give the last word to Tom Lehrer.