Generally speaking, an ultimatum means war, at least in situations involving medieval states such as Iran and Saudi Arabia. If Iran issues such an ultimatum the Saudis would be bound to ignore it because should they obey they would be opening the door to revolution inside the Arabia itself. It must be understood that the Saudis have but a tenuous hold on power in Arabia, and their intervention in Bahrain - a puny kingdom on the coast of Arabia - was absolutely necessary to avoid revolution across the peninsula.
In the first Gulf War America established military bases in Saudi Arabia to protect that nation from invasion by either Iraq or Iran. It was that act that enraged Osama Bin-Laden (by his own admission) because Islam commanded that no foreigner soldiers trod the "holy soil" of Arabia. It did not matter that those troops were there to help and protect the inhabitants of Arabia; Bone-Laden is a literalist, and he wanted an excuse to launch a jihad. This provided the excuse, and Al-Qaeda launched a war that went largely unnoticed by America (particularly Bill Clinton) for the better part of a decade. Three thousand Americans died in New York as a result of that inattention, and now there is a global war of jihad and counter-jihad being waged. Al-Qaeda is particularly interested in removing the House of Saud, which Bin-Laden sees as a hindrance to the coming of an Islamic Caliphate. Iran sees the Saudis as a hindrance as well, a hindrance to the total war that must come if the 12th Imam (that dude who fell down a well) is to return, the Islamic version of the Second Coming of Christ. Iran wants all out war.
But what happens if Shia Iran invades Sunni Arabia? Have a look at
this map.
Bear in mind, Iran would have to be most careful in the event of war; Saudi Arabia is home to the many shrines of Islam, and Mecca cannot be touched at all. Should Iran bomb the Saudis they would have to circumscribe their attacks to avoid destroying a place that is sacred, and most of Arabia is sacred to Islam. Nothing would prevent the Saudi government from setting up at some shrine to avoid being hurt.
All-out war in the Islamic world
And, given the distribution of Shia to Sunni, an invasion would likely trigger all-out war in the Islamic world.
The Shia/Sunni split is an ancient one, and a bitter one at that. It goes back to shortly after Muhammad’s death. It is not theological as are the splits in Christendom, as Islam really has no theology. It's an ancient power struggle; When Muhammad died Abu Bakhr was elected Caliph, and the word Sunni means "one who follows the traditions of the Prophet". This election was disputed by a sizable group who believed that Ali, Muhammad’s cousin and son-in-law, should have been made the head, and Shia is short for Shia-t-Ali, or "of the party of Ali". They are sometimes called Ahl-al-Bayt, or "people of the household" since they supported keeping power in Muhammad’s family. The Shia broke with the Sunni, and separation has led to differences in customs and practices. This was a Schism, much like the break between Catholic and Orthodox, rather than a break in theology as in the Protestant Reformation. Again, there really is no theology in Islam.
85% of Moslems are Sunni.
A war in the Islamic World would likely see the extermination of the Iranian regime.
In some ways, such a war would be a good thing from our perspective; the terror master of Iran would wind up being destroyed, in all probability, and the Mujihadeen would all fight in this global war against each-other rather than plot mischief against the West. The money used to finance Jihad would be turned to funding an Islamic war, and this pan-Islam would shatter. However, there would be huge problems with this; the flow of oil would be cut off, likely leading to a worldwide depression. This alone is dire enough to draw in the great powers, and that would likely lead to more hatred of the West. Israel is always a handy target, and it seems likely Iran would do something to split some Sunni off from defending the Saudis, perhaps destroy Tel Aviv or some other horrible thing, drawing Israel into the conflict. Even if it ended reasonably well, we would have trained a whole generation of warriors. Remember, the Civil War here in the U.S. was fought by men trained in combat in Mexico, and all the names we have come to associate with the War Between the States fill the rosters of the troops of Winfield Scott and Zach Taylor. These guys knew how to fight, which made the Civil War so bloody. Had there not been a Mexican War, there may well have been a much milder Civil. A worldwide Islamic conflict will train and equip and militarize a whole generation, one which will be seeking a challenge. Invade Israel? Invade Europe? Russia? The sky would be the limit.
And a worldwide depression would see radical changes at home, and likely not for the better. Desperate people will follow a strong leader who can deliver aid to them; look at Germany during the Depression. Here in America we followed a quasi-socialist path despite all of our heritage and traditions that celebrated self-reliance and liberty. We are not the men who lived in the 1930's; half of all young people see
nothing wrong with socialism, according to a recent Rasmussen poll.
One need but look at the hew-and=cry centered around Wisconsin's attempt to rein in benefits spending for public sector workers to see that revolution wouldn't be far off in a second Great Depression. Granted, what happened in Wisconsin was to a large degree astro-turfed, but still there were a lot of very angry and destructive people prepared to do whatever it takes to get their way. Now multiply that by a factor of 50 (in all states) and you have the recipe for tyranny; a new Adolf Hitler could well arise, one who has cut his teeth in the Public Unions, say, and where would we be? There would be civil war. Yes, the Tea Party types would fight them, but such wars are generally won by the most organized, disciplined group, not by those who are right. The Left has been preparing for such a scenario for a long time.
This is a dire threat.
