The empire this book opens with was built by a people who took someone else's throne, someone else's capital region, and very nearly someone else's name — and then made all three into something the previous owners would not have recognized.

Start with the ground. The Eurasian steppe is a belt of open grassland that runs, almost unbroken, from the plains north of the Black Sea to the edge of Manchuria, several thousand miles of wind-combed grass with too little rain for farming and exactly enough for grazing. A people who could turn that grass into horses, sheep, and mounted archers could field armies that no settled kingdom could catch and few could beat. The catch was that grass is not silk, iron, grain, or books: a steppe power that wanted those things had to take them from, or trade them with, the farming civilizations on its rim, above all China. Every empire in this book is some answer to that single problem — how a grass economy gets the products of a grain economy — and the answers run from extortion to conquest to, eventually, simply moving into the oasis towns and becoming the farmers and merchants themselves.

Within that vast belt, one stretch of it was the steppe's throne room: the valley of the Orkhon (OR-khon) River, in the heart of what is now Mongolia, sheltered by a sacred wooded massif the Turkic peoples called the Ötüken (UH-tuh-ken). Whoever held the Orkhon was understood, by steppe people themselves, to hold the legitimate center of nomadic power, the way "Rome" meant more than a city. The Xiongnu (the first great steppe empire, the mounted confederation that fought Han China to a standstill more than a thousand years before this story, Xiongnu & Huns) had ruled from near here; so had the Türks (Göktürk Khaganate). To take the Orkhon was to claim the steppe's equivalent of a crown, and that is precisely what the Uyghurs did in 744.

The people who held it before them were the Türks — specifically the Second Türk Khaganate, ruled by the Ashina clan, the dynasty that had given the world the very word Turk and the first empire to use it as a name for itself (Göktürk Khaganate). By the 730s the Second Türk Khaganate was the steppe's reigning power but a brittle one, its later qaghans weak, its subject tribes resentful and over-taxed in the only currency nomads have, which is loyalty. The largest block of those resentful subjects was a loose grouping of Turkic-speaking tribes the Chinese sources lump together as the Tiele (TYEH-luh) — kin to the ruling Türks in language and way of life, as a Dane is kin to a German, but politically a conquered underclass. Among the Tiele, one tribal confederation was rising: the Uyghurs (OO-ee-gur, also written Uighur), led by a clan called the Yaglakar.

It is worth being honest about how little of the Uyghurs' own early story survives in their own words, and how much in their enemies'. The Chinese knew them as a Tiele tribe that had supplied cavalry, sometimes to the Türks, sometimes against them, for over a century. The Uyghurs' own account, cut into stone a generation later, naturally tells it as destiny. The plain version both can agree on is this: around 742 three of the Türks' subject peoples — the Uyghurs, the Karluks (KAR-luk), and the Basmyl (BAHS-mil) — rose together, and the Second Türk Khaganate, already rotten, could not put them all down at once.

What followed is a small masterclass in steppe politics. The three rebel peoples won, and then immediately turned on each other to decide who would actually inherit the Orkhon. The Basmyl took the title first; within two years the Uyghurs and Karluks destroyed the Basmyl. The Uyghurs and Karluks then divided the spoils, the Karluks taking the western steppe (file that away — it is the seed of Chapter 6) and the Uyghurs taking the center. In 744 the Uyghur leader Qutlugh Bilge Köl (koot-LOOG BILL-geh KUL) proclaimed himself qaghan on the Orkhon, and in 745 his forces killed the last Ashina qaghan, Özmiş (UHZ-mish), and sent his head to the Tang court in China as both a trophy and a diplomatic announcement: the management has changed; deal with us now.

That head mattered more than it seems. By delivering the last Türk ruler's head to Tang China — the long, brilliant Chinese dynasty that ran from 618 to 907 and was, in the 740s, at the height of its wealth and confidence (Tang–Song China) — the new Uyghur qaghan was performing a careful piece of theater. He was telling the richest empire on earth that the Uyghurs were the Türks' legitimate successors, a stable address China could trade with and hire, not just another raiding nuisance. The relationship that opened with that severed head would, within fifteen years, make the Uyghurs the creditors of the Tang and is the whole subject of Chapter 2.

Qutlugh Bilge Köl died in 747, and the empire's real builder took over: his son, who reigned as Bayanchur Khan (BUY-an-chur), titled El Etmish Bilge Qaghan, "the state-organizing wise qaghan," and the title was earned. Over roughly the next dozen years Bayanchur turned a victorious tribal coalition into an actual state, and he did it with two instruments that tell you immediately this was not going to be an ordinary nomad empire: a city, and an alphabet's worth of writing.

The city was Ordu-Baliq (OR-doo BAH-lik), "the city of the court," raised about 200 miles (320 km) west of modern Ulaanbaatar on the Orkhon and known to later ages by its Mongol name, Karabalgasun, "the black ruins." A walled, gridded, permanent capital with a citadel, markets, and craftsmen's quarters was a genuinely strange thing for a steppe empire to build. The whole logic of nomad power was mobility: you could not besiege a people who had no fixed place to defend. By planting a capital, Bayanchur was trading away some of that invulnerability for something he wanted more — a fixed point where tribute could be collected, foreign merchants and ambassadors received, scribes housed, and the qaghan's wealth and prestige put permanently on display. It was a bet that the Uyghur empire would make its money less from raiding than from being a stable hub that taxed and protected trade, and that bet shaped everything that followed, including the religion the court would adopt (Chapter 3) and, ultimately, the speed with which the whole thing could be destroyed when an enemy finally did have something to burn (Chapter 4).

The writing is the other tell. The Türks before them had cut monumental inscriptions in a runiform Old Turkic script, and the Uyghurs continued the practice on a grand scale. Bayanchur left at least two great inscribed stelae — known today, from where they were found, as the Shine Usu and Tariat inscriptions — that narrate his campaigns and the founding of the khaganate in the Uyghurs' own language and their own voice. These stones are the thin inside-voice the introduction promised: almost everything else in this chapter is Chinese testimony, but here, for a few hundred lines, the Uyghurs speak for themselves, in the formulaic, boastful, surprisingly moving register of steppe royal memory ("I had walls built there; I had the eternal stone inscribed"). It is the difference between a credit report and a diary, and the historian needs both.

The state Bayanchur organized rested on a tribal skeleton the sources call the Toquz Oghuz (toh-KOOZ oh-GOOZ), "the Nine Tribes" — the nine-clan core of the confederation, with the royal Yaglakar at its head and a fixed order of precedence beneath. This is the answer to a question steppe history constantly raises and rarely answers cleanly: when a nomad "empire" appears overnight, what actually holds it together between campaigns? For the Uyghurs the honest answer, as far as the inscriptions and Chinese reports let us reconstruct it, is the Toquz Oghuz hierarchy plus the qaghan's ability to keep delivering two things — military success and a cut of the China trade. Remove either and the confederation could come apart as fast as it had come together, which is exactly what Chapter 4 records.

It is worth placing the Uyghur Khaganate in the world of its own moment, the way this project does at every "first" or "only," because the steppe is usually told as if it ran on a separate clock, and it did not: 744 sits in one of the most consequential decades of the premodern world, a fact the Uyghurs' later obscurity hides. Two events of that decade are load-bearing for this whole book. In 750 the Abbasid Revolution overthrew the Umayyad caliphs and founded the Baghdad-centered, Persianized, Silk Road–wired Islamic world that the western half of this book eventually joins (Islamic Golden Age). The next year, 751, an Abbasid and a Tang army collided at the Battle of Talas, in the Karluk country west of the Uyghurs; the Karluks' mid-battle defection helped hand Central Asia's future to Islam rather than China, the single clearest hinge in this book, and it happens offstage here to people who will not matter until Chapter 6. Everything else in the decade is backdrop to those two: the Tang were four years from the catastrophe that would make the Uyghurs rich (Chapter 2), and a far poorer, far less urban Frankish order was a generation away from Charlemagne (Early Medieval Europe). The Uyghur Khaganate was born into the same years as Abbasid Baghdad and Carolingian Francia, and it outlasted neither in fame, only in consequence.

By around 760, then, the picture was set. A Turkic people who were not the Türks held the Orkhon, the steppe's throne. They ruled from a walled city, kept written records of themselves, organized power through the Nine Tribes, and had announced themselves to China by couriering it the head of the last emperor they had replaced. Everything that made this empire unusual — that it was urban, literate, mercantile, and would soon be the only steppe empire in history to adopt a scriptural missionary religion of the settled world — is already visible in embryo in what Bayanchur built.

None of it yet explains how a grass empire got rich enough to pay for stone cities and a state church. That money did not come from the grass. It came from a disaster four years downriver, in the heart of Tang China, where a general named An Lushan was about to set the richest empire on earth on fire — and the Uyghurs were about to charge an extraordinary price to help put it out.

The Uyghur & Qara-Khitai Steppe

The Khaganate That Replaced the Turks

Creditors of the Tang

A Persian Religion on the Steppe

Destroyed in a Generation

From Khaganate to Oasis

The First Turkic Muslims

The Buddhists Who Ruled the Muslims

The Eve of the Mongols