#sunnis

It's a good question and there are a number of complex reasons why that didn't/doesn't happen which require a much deeper dive, but I'll try to give a simplified answer. First of all, the caliph was the spiritual leader of the entire Muslim world and while the caliphs also had a political role as successors to Muhammad, that role changed dramatically through the centuries as the Muslim world grew, Islamic empires rose and fell, and Islam itself branched into different sects. The last widely-recognized caliphs were the Sultans of the Ottoman Empire, but even in the last decades of the Ottoman Empire, there were disagreements throughout the Muslim world about the legitimacy of anyone's claim on the caliphate. The two main branches of Islam -- Sunni and Shia -- have entirely different ideas on how a caliph should be chosen and who the caliph is chosen by.

When the Ottoman Empire collapsed after the end of World War I, the Sharif of Mecca -- Hussein, a direct descendant of Muhammad as the leader of Hashemite dynasty (and great-great grandfather of the current Jordanian King Abdullah II) -- attempted to declare himself the new caliph, but was not accepted. In many ways, it was like a modern European monarch suddenly declaring himself the Pope; that's just not how most Muslims believed the spiritual leader of the Islamic faith should be determined. Plus, Hussein only had a tenuous hold on Islam's holiest sites (Mecca, Medina, and, at the time, Jerusalem) following World War I, and Abdul Aziz Ibn Saud was in the process of taking control of what is now Saudi Arabia. Once Ibn Saud became King of Saudi Arabia, he took over as "Custodian of the Two Holy Mosques" (Mecca and Medina), but the idea of declaring himself caliph was out of the question. Ibn Saud and the vast majority of his supporters were members of the deeply conservative, puritanical Wahhabi sect of Sunni Islam and they believed that the caliph was chosen by all Muslims, not declared by one person. As the guardian of Islam's two holiest sites, the King of Saudi Arabia is responsible for ensuring that all Muslims capable of making the Hajj pilgrimage to Mecca (and the lesser pilgrimage to Medina) can do so. Unilaterally declaring himself the caliph would undoubtedly have alienated many Muslims, particularly those from countries outside of Saudi Arabia and especially Shiites. In other words, it's not within the power of the King of Saudi Arabia to give himself (or any other individual) the title of caliph, and he'd probably get just as much resistance from his fellow Saudis if he tried to do so. There's no way that the Ikhwan -- the ascetic tribes and Bedouins who largely acted as Ibn Saud's military forces as he conquered most of the Arabian Peninsula in the first half of the 20th Century -- would have remained loyal to the first Saudi King if he had unilaterally proclaimed himself the caliph.

"In numerous cases of apparently ethno-nationalist conflict, the deepest hatreds are manifested between people who — to most outward appearances — exhibit very few significant distinctions. It is one of the great contradictions of civilization and one of the great sources of its discontents, and Sigmund Freud even found a term for it: “the narcissism of the small difference.” As he wrote, “It is precisely the minor differences in people who are otherwise alike that form the basis of feelings of hostility between them...

The partition of India and Pakistan, for example, which gives us one of the longest-standing and most toxic confrontations extant, involved most of all the partition of the Punjab. Visit Punjab and see if you can detect the remotest difference in people on either side of the border. Language, literature, ethnic heritage, physical appearance — virtually indistinguishable. Here it is mainly religion that symbolizes the narcissism and makes the most of the least discrepancy.

I used to work in Northern Ireland, where religion is by no means a minor business either, and at first couldn’t tell by looking whether someone was Catholic or Protestant. After a while, I thought I could guess with a fair degree of accuracy, but most of the inhabitants of Belfast seemed able to do it by some kind of instinct. There is a small underlay of ethnic difference there, with the original Gaels being a little darker and smaller than the blonder Scots who were imported as settlers, but to the outsider it is impalpable. It’s just that it’s the dominant question locally.

Likewise in Cyprus, it is extremely hard to tell a Greek from a Turk. The two peoples have been on the same island for so long that they even suffer from a common sickle-cell blood disease called thalassemia. I once interviewed a doctor who specialized in the malady, and he solemnly told me that, from a blood sample, it was not possible to tell if the donor was Greek or Turkish. I had to stop myself from asking him if he had hitherto thought that different nationalities were made out of different genetic material. There have been almost no recorded cases of intermarriage between Greek and Turkish Cypriots, and the island remains sternly partitioned.

In his book The Warrior’s Honor, Michael Ignatieff spent some time trying to elucidate what it was that made soldiers in the Balkan Wars — physically indistinguishable from one another — so eager to inflict cruelty and contempt upon Serb or Croat or Bosnian, as the case might be. Very often, the expressed hatred took the form of extremely provincial and local rivalries, inflamed by jealousies over supposed small advantages possessed by the other. Of course, here again there are latent nationalist and confessional differences to act as a force multiplier once the nasty business gets started, but the main thing to strike the outsider would be the question of “How can they tell?” In Rwanda and Burundi, even if it is true, as some colonial anthropologists used to claim, that Hutu and Tutsi vary in height and also in the delimitation of their hairlines, it still doesn’t seem enough of a difference upon which to base a genocide.

In Sri Lanka, where again it takes a long time to notice that Tamils are prone to be slightly smaller and slightly darker than the Sinhala majority, it is somehow the most important information that either population possesses. And it doesn’t take long for one population to start saying that the other one has too many children, takes too much leisure, is too casual about hygiene. Every time he heard a Shiites or Sunni Iraqi saying that religion didn’t really count, said my friend Patrick Cockburn in his book on Baghdad, he noticed that every single one of them knew the exact faith allegiance of everybody else in the room. And if you want to see an expression of sheer racial disdain, try giving to an Iranian Shiites the impression that you think he and his Iraqi co-religionists are brothers under the skin.

The next example of this phenomenon will be among the most serious as well as the least dramatic. One of the most unobtrusive differences in the world—the line that separates French from Flemish-speaking Belgians—is about to be forcefully reasserted in a bid to split Belgium in two. If this secession occurs, then the headquarters country of NATO and the European Union will rather narcissistically cease to exist, undone by one of the smallest distinctions of all.

So pity the Uzbeks and Kyrgyz as they peer suspiciously at one another during a sudden time of scarcity and insecurity. Their mutual miseries may be just beginning. And all this contains the true ingredients of tragedy—and of irony. One of the great advantages possessed by Homo sapiens is the amazing lack of variation between its different “branches.” Since we left Africa, we have diverged as a species hardly at all. If we were dogs, we would all be the same breed. We do not suffer from the enormous differences that separate other primates, let alone other mammals. As if to spite this huge natural gift, and to disfigure what could be our overwhelming solidarity, we manage to find excuses for chauvinism and racism on the most minor of occasions and then to make the most of them. This is why condemnation of bigotry and superstition is not just a moral question but a matter of survival."