Another quicky, inspired by
https://www.alternatehistory.com/discussion/showthread.php?t=104748&highlight=thrones. befoe it's back to 9-5 for me.
It's AD 2008 or AH 1430 or 5768 after the creation of the world or variously the seventeenth year of the lung Emperor's rule or the Year of the Earth Rat or the year 2229 since Quin Shihuang unified China.
Although the Four Thrones have seen their ups and downs over the last twelve centuries, they have never been destroyed. Dynasties succeeded eachother on the Chinese and Islamic thrones, often rather chaotically, but control of the core territories was never lost to outsiders, although the Chinese of the 12th and 13th centuries had to temporary withdraw south of the Yangste. The Khazars suceeded in their long crusade to bring the Holy Book to the various nomadic and pastoral peoples of the east, and even converted Ubchik Khan when he swept west to central Europe in the late 1200's, expanding under Khan David VII into the power vaccum left by his ravaging of the Balkans. The Emperors of Europe managed to establish the principle of primogeniture, and over the centuries slowly established their supremacy over the many dukes and counts and barons.
Nowadays, a fragile peace has been in place for over half a century, since the long, bloody, machine-guns-and-barbed wire struggle for India between Caliph and Son of Heaven ended with a thin and pawky Chinese victory after tens of millions of deaths.
Nobody is really interested in a major war: the Khazars, the smallest if most closely unified of the powers, aren't really willing to take a stab at liberating Jerusalem unless _both_ the Chinese and the HRE are ready to join in: the HRE doesn't really like the Khazars much (dirty Jews and co-destroyers of the old Byzantine empire) and neither do the Chinese (Monotheists are _always_ desruptive, and if it weren't for the Khazars, Eastern Siberia and north Manchuria would be what they rightlfully should be - Chinese).
The increasingly secular HRE is more interested in trade than in military expansion nowadays, and the border between Islamic and Christian Spain is nowadays almost as open as that between Canada and the US OTL. Admittedly, Muslims _are_ a bunch of dammed heretics and sneaky and corrupt, but they have good stuff to buy and sell. The Chinese have never really been big on conquest for it's own sake, and the sufi-influenced religion of most of the Caliphate has for long emphasized the importance of Inner Jihad over Outer Jihad. (Mexico trading sides four times over the 19th century, once in exchange for 200,000 square miles of tropical jungle, rather stregnthened the notion of the pointlessness of warfare, and the Indian war really put the cherry on top).
It's a more tolerant world than it used to be: Muslims and Jews are actually allowed to do Jew-y and Muslimesque things
right out in public nowadays in most parts of the HRE, and the Khan of the Khazars has proclaimed that Jews from the fourteen proscribed sects will be allowed to return to the empire, as long as they keep quiet. (The Khanate accepts eight schools of Judaism as either correct or acceptable: others, less so. Although the majority of the world's Jews live in the Holy Khanate, a good 5-6% live elsewhere, mostly in Islamic lands. Travel is fairly easy, and each of the four empires is so certain of their superiority to the others in some major way or another than travelers are unlikely to suffer persecution at the hands of spite-filled locals.
An early spread of literacy and printing, easier travel, and the willingness of at least three of the empires to allow traders and travellers from wherever to pass through their lands (and the HRE too, after the cross-polinization of the greek diaspora and the fascination with the old Empire on the parts of the emperors Maxmillian III and Ignatz II led to the
Renaissance) all contributed to an easier spread of knowledge than in our world, and a more rapid trasnmittal of ideas and technolgies. Scientific thought first arose in the Islamic lands, but in the resource-poor middle east, was slow to help spark an industrial revolution, while Europeans and Chinese were faster to pick up on the interesting things one could do with coal and iron.
Today, the oceans are busy with steamships, Asia and Africa are closely patterned with rail and telegraph lines, and the oil-rich Islamic lands are bustling with automobiles. An old earth and evolution are grudgingly accepted among the educated and scholarly in all the empires, although the teaching of evolution is still banned in the Sultanate of Delhi. And some scholars in Cairo are beginning to work out some of the more remarkable properties of some rare heavy metals...