The success of the Mongols in ruling vast territories was due in large part to their willingness to incorporate other ethnic groups into their armies and governments. Whatever their original country or religion, those who served the Mongols loyally were rewarded. Uighurs, Tibetans, Persians, Chinese, and Russians came to hold powerful positions in the Mongol governments. Chinese helped breach the walls of Baghdad in the 1250s, and Muslims operated the catapults that helped reduce Chinese cities in the 1270s.

Since, in Mongol eyes, the purpose of fighting was to gain riches, the Mongols would regularly loot the settlements they conquered, taking whatever they wanted, including the residents. Land would be granted to military commanders, nobles, and army units to be governed and exploited as the recipients wished. Those working the land would be given to them as serfs. The Mongols built a capital city called Karakorum in modern Mongolia, and to bring it up to the level of the cities they conquered, they transported skilled workers from those cities. For instance, after Bukhara and Samarkand were captured in 1219–1220, some thirty thousand artisans were enslaved and transported to Mongolia. Sometimes these slaves gradually improved their status. A French goldsmith from Budapest named Guillaume Boucher was captured by the Mongols in 1242 and taken to Karakorum, where he gradually won favor and was put in charge of fifty workers to make gold and silver vessels for the Mongol court.

The traditional nomad disdain for farmers led some commanders to suggest turning north China into a gigantic pasture after it was conquered. In time, though, the Mongols came to realize that simply appropriating the wealth and human resources of the settled lands was not as good as extracting regular revenue from them. A Chinese-educated Khitan who had been working for the Jurchens in China explained to the Mongols that collecting taxes from farmers would be highly profitable: they could extract a revenue of 500,000 ounces of silver, 80,000 bolts of silk, and more than 20,000 tons of grain from the region by taxing it. The Mongols gave this a try, but soon political rivals convinced the khan that he would gain even more by letting Central Asian Muslim merchants bid against each other for licenses to collect taxes any way they could, a system called tax-farming. Ordinary Chinese found this method of tax collecting much more oppressive than traditional Chinese methods, since there was little to keep the tax collectors from seizing everything they could.

By the second half of the thirteenth century there was no longer a genuine pan-Asian Mongol Empire. Much of Asia was in the hands of Mongol successor states, but these were generally hostile to each other. Khubilai was often at war with the khanate of Central Asia, then held by his cousin Khaidu, and he had little contact with the khanate of the Golden Horde in south Russia. The Mongols adapted their methods of government to the existing traditions of each place they ruled, and the regions went their separate ways.

In China the Mongols resisted assimilation and purposely avoided many Chinese practices. The rulers conducted their business in the Mongol language and spent their summers in Mongolia. Khubilai discouraged Mongols from marrying Chinese and took only Mongol women into the palace. Some Mongol princes preferred to live in yurts erected on the palace grounds rather than in the grand palaces constructed at Beijing. Chinese were treated as legally inferior not only to the Mongols but also to all other non-Chinese. In cases of assault the discrepancy was huge, as a Mongol who murdered a Chinese could get off with a fine, but a Chinese who hit a Mongol to defend himself would face severe penalties.

In Central Asia, Persia, and Russia the Mongols tended to merge with the Turkish groups already there and, like them, converted to Islam. Russia in the thirteenth century was not a strongly centralized state, and the Mongols allowed Russian princes and lords to continue to rule their territories as long as they turned over adequate tribute (thus adding to the burden on peasants). The city of Moscow became the center of Mongol tribute collection and grew in importance. In the Middle East the Mongol Il-khans (as they were known in Persia) were more active as rulers, again continuing the traditions of the caliphate. In Mongolia itself, however, Mongol traditions were maintained.

Mongol control in each of the khanates lasted about a century. In the mid-fourteenth century the Mongol dynasty in China deteriorated into civil war, and in the 1360s the Mongols withdrew back to Mongolia. There was a similar loss of Mongol power in Persia and Central Asia. Only on the south Russian steppe did the Golden Horde maintain its hold for another century.

As Mongol rule in Central Asia declined, a new conqueror emerged, Timur, also known as Tamerlane (Timur the Lame). Not a nomad but a highly civilized Turkish noble, Timur in the 1360s struck out from his base in Samarkand into Persia, north India (see “The Delhi Sultanate”), southern Russia, and beyond. His armies used the terror tactics that the Mongols had perfected, massacring the citizens of cities that resisted. In the decades after his death in 1405, however, Timur’s empire went into decline.