By 1294, the Mongol Empire was four states, and the surprising thing about that fragmentation is that it produced the most connected century Eurasia had ever experienced.

The political fact is that after the Toluid Civil War the empire had stopped being a single state. The Yuan, the Ilkhanate, the Golden Horde, and the Chagatai Khanate were each governing independently, fighting each other intermittently, converting to different religions, and building separate capitals. By any conventional measure of imperial coherence, the Mongol Empire after 1264 had failed.

The economic and cultural fact is that, despite all of this, long-distance trade, diplomatic exchange, and intellectual transmission across the four khanates were operating at a level that nothing in pre-modern Eurasian history had matched. Merchants moved from Italy to China and back. Persian astronomers corrected Chinese calendars. Chinese paper money was studied at the Ilkhan court. A Moroccan traveler could spend thirty years touring four continents on Mongol roads. This system has a name: the Pax Mongolica, the "Mongol Peace," and it is the organizing premise of this chapter. Each of the four khanates is a case study in how a fragmenting political order can still hold a continental trade system together — and in how each khanate, in its own way, was being absorbed by the cultures it had conquered while keeping the trade infrastructure running.

The four khanates cooperated more often than they fought. They recognized each other's senior khans (with certain exceptions). They allowed merchants, missionaries, and diplomats to cross each other's territories under the protection of imperial paiza tablets. And they shared a kinship structure (every senior ruler in every khanate was a descendant of Genghis Khan or a Genghisid son-in-law) that gave the system a kind of constitutional family logic. The Mongol Empire after 1264 was not a centralized state. It was a confederal dynastic system held together by a dwindling but real shared identity, and a working trade infrastructure that paid the bills.

This chapter examines each khanate in turn, looking for what the Pax Mongolica did to the conquerors as well as to the conquered.

The Yuan dynasty in China and Mongolia was the largest and richest of the four. Population perhaps eighty to a hundred million people — a number that includes the dramatic demographic losses of the conquest period, after which the Chinese population was substantially reduced from late-Song highs. The Yuan governed China through a hybrid bureaucracy that combined Mongol decimal-military structures at the top with Chinese-style ministries below. The political ranking of subjects under Yuan law was famously stratified by ethnic category: Mongols at the top, Semu ("various sorts" — non-Han non-Mongol Asians, especially Central Asian Muslims and Persians serving as administrators and merchants) second, Hanren (northern Chinese, who had been under foreign rule longer and were considered more reliable) third, and Nanren (southern Chinese, the recently conquered Song subjects) fourth. The system was not as rigid in practice as it sounds on paper — many Chinese officials served at high levels — but it produced significant resentment among the Han Chinese gentry, particularly the southern gentry whose paths to power through the traditional civil-service examination were closed for most of the Yuan period.

The closure of the examination system had cultural consequences. Educated Chinese who could not enter the bureaucracy turned to other forms of expression. The most consequential was the explosion of zaju (TZAH-joo) drama — the form of Chinese theater combining music, dialogue, dance, and acrobatics — which became the leading literary form of the Yuan period. Playwrights like Guan Hanqing wrote works such as The Injustice to Dou E, dramas of social commentary and emotional depth that are still performed today. The vernacular novel — including early versions of Romance of the Three Kingdoms and Water Margin — also developed in this period as another channel for Chinese literary energy locked out of the bureaucracy. Chinese culture under Yuan rule produced some of its most enduring popular forms in part because the political ladder for educated Chinese had been chopped off.

Yuan economic innovation was extensive. Kublai's Chao (CHOW) paper currency — backed by silver and silk reserves and made the sole legal tender of the empire — was the largest and most successful paper money operation of the medieval world. By the early fourteenth century, copper coins were rarely used in major commercial transactions in China; everyone used paper. The system worked beautifully for fifty years, then broke down when the late Yuan court began over-issuing currency to cover military and infrastructure expenses, leading to dramatic inflation. Marco Polo described the paper money operation with unconcealed astonishment: a piece of paper, declared by the emperor to be worth a certain weight of silver, accepted by everyone in the empire as if it actually were that weight of silver. In thirteenth-century Europe such a system was unimaginable.

The Yuan also extended the Grand Canal (the major north-south inland waterway of China) to run from Hangzhou directly to Khanbaliq, rerouting older Sui and Tang segments and adding new sections to bring grain barges from the Yangtze valley straight to the Mongol capital. The completed canal was approximately 1,100 miles (1,800 km) long and served as the economic artery connecting the agriculturally rich south to the politically central north. It would remain the spine of Chinese internal commerce until the construction of railways centuries later.

The Yuan court patronized one of the most accurate astronomical observatories in the medieval world. The astronomer Guo Shoujing (GWAW SHOH-jing) — working in collaboration with Persian astronomers from the Maragheh tradition (see Ilkhanate below) — produced the Shoushi calendar in 1281, calculating the length of the solar year to within 26 seconds of the modern figure. The Shoushi calendar was the most accurate calendar in the world at the time and remained in official use in China for over three centuries.

The Ilkhanate (IL-kah-nate, "subordinate khanate") in Persia and Iraq was the second-largest of the four states. Population perhaps fifteen to twenty million. Capital first at Maragheh, later at Tabriz in northwestern Iran, eventually at Sultaniyya.

The Ilkhanate is the khanate where the cultural-resurrection pattern that the Persian Empire narrative documents (Persian Empire Chapter 10 — the Persian habit of culturally absorbing every conqueror) operated most clearly. The Ilkhans were Mongols who within two generations were ruling as Persian-style monarchs. Ghazan Khan (reigned 1295–1304), the seventh Ilkhan and the most consequential, converted to Islam publicly in 1295, made it the Ilkhanate's official religion, took a Muslim name (Mahmud), and adopted Persian-style royal protocols. His chief minister Rashid al-Din Hamadani (rah-SHEED al-DEEN), a Jewish-born physician who converted to Islam and became one of the most extraordinary administrators of the medieval period, ran the Ilkhanate's tax reform, agricultural revival, and cultural patronage program for two decades.

Rashid al-Din's most enduring legacy was a literary one. He compiled the Jami' al-tawarikh (jah-MEE al-tah-WAH-reekh, "Compendium of Chronicles"), completed around 1307. The Compendium is, by serious scholarly consensus, the first true world history. (A striking minor connection: Rashid al-Din corresponded with Safi al-Din of Ardabil, the founder of the Safavid religious order — the dynasty that would unify Iran two centuries later was already a presence at the Ilkhan court, Safavid Persia Ch 1.) It contains the histories of the Mongols (drawing on documents at the Ilkhan court that have not survived elsewhere), the Chinese (drawing on Chinese historians whom Rashid al-Din consulted directly), the Indians, the Jews, the Christian Europeans (Rashid al-Din corresponded with European clerics), the Muslims, and the pre-Islamic Iranians. It is illustrated, in surviving manuscripts, with miniatures that synthesize Persian, Chinese, and Byzantine artistic traditions in a new style. No historian before Rashid al-Din had attempted to write a single work covering all of the world's major civilizations using sources from each. The work is one of the great scholarly products of the Pax Mongolica, made possible by an empire that physically connected the source materials for the first time.

The other extraordinary cultural product of the Ilkhanate was the Maragheh Observatory (mah-RAH-geh), founded by Hülegü Khan in 1259 and led by Nasir al-Din al-Tusi (the same scholar Hülegü had rescued from Alamut, Chapter 5). Maragheh was, in its day, the most sophisticated astronomical observatory in the world. It contained a 14-foot mural quadrant, an armillary sphere, a parallactic ruler, and instruments for systematic stellar observation. Al-Tusi and his successors compiled the Zij-i Ilkhani (zeej-ee il-KAH-nee), a set of astronomical tables that corrected long-standing errors in Ptolemaic astronomy. Al-Tusi's mathematical work — including the Tusi couple — produced solutions to problems in planetary motion that fed forward, through transmission via Greek-speaking refugees in the Byzantine and Renaissance worlds, into the work of Copernicus three centuries later. Specific Copernican diagrams in De Revolutionibus (1543) match al-Tusi's diagrams in suspicious detail. The transmission lineage is debated but the visual coincidence is striking.

The Ilkhanate also produced Sultaniyya (sool-tah-NEE-yah), the planned capital city built by Ilkhan Öljaitü (uhl-JAY-too, Ghazan's brother and successor) in the early 1300s. Sultaniyya's centerpiece was Öljaitü's mausoleum, a massive double-shell dome — one of the most ambitious architectural feats of the medieval world, and a clear ancestor of the great domed mausoleums of later Persian and Indian Islamic architecture, including the tilework domes of Safavid Isfahan in the early seventeenth century (Safavid Persia Ch 4) and, eventually, the Taj Mahal. The dome stands today, partly restored. It is one of the most underrated buildings in world architectural history.

The Ilkhanate's political end came in 1335 with the death of Ilkhan Abu Sa'id (ah-BOO sah-EED) without an heir. The khanate fragmented into competing dynasties — the Jalayirids, Chobanids, Muzaffarids — none of which could reunify Persia. Persia would remain politically fragmented until Timur rebuilt a centralized state through conquest in the 1370s (Chapter 9), and then fragmented again after the Timurids faded. The next unified Iranian state was the Safavid dynasty (1501), which inherited the Ilkhanate's former capital at Tabriz, the Tabriz school of miniature painting, and the institutional networks of Shia scholarship the Ilkhanate had helped sustain (Safavid Persia Ch 1).

The Golden Horde (so called from the Russian translation of the Mongol Altan Ordu, "Golden Tent" or "Golden Camp," the name of the senior khan's enormous ceremonial pavilion; the term came into Western usage centuries later, but it does correspond to the Mongol original) ruled the Kipchak Steppe (the grasslands of modern Russia, Ukraine, and Kazakhstan) and the Russian principalities. Capital at Sarai on the lower Volga. Population mostly Turkic-speaking steppe nomads with a substantial Slavic agrarian base in the Russian principalities.

The Golden Horde governed Russia through what later Russian historians called the Tatar Yoke: a system of tribute extraction in which the Russian princes were confirmed in office by the khan in Sarai, paid annual tribute (in silver, furs, and conscripted soldiers), and were periodically replaced when they displeased the khan or when a rival prince outbid them. The Russian Orthodox Church was exempt from taxation by Mongol decree (the Yassa's religious-tolerance principle, applied in practice) and used the period of foreign overlordship to consolidate its institutional position — the Mongol period is when Moscow began its rise to dominance in Russian church and state, partly because the Moscow princes were better than their rivals at managing the relationship with Sarai.

The Golden Horde's economic base was its position as the middle stretch of the trans-Eurasian trade corridor. From the late thirteenth century onward, Genoese and Venetian merchants operated trading colonies on the northern Black Sea coast — most importantly Caffa (modern Feodosia in Crimea), granted to Genoa around 1267. Caffa funneled Chinese silks, Persian spices, and Central Asian slaves into Mediterranean markets, and brought European silver and craft goods east. The Genoese-Mongol commercial relationship was one of the most important economic partnerships of the late thirteenth century, and it would matter dramatically for what was about to happen with the plague (Chapter 8).

The Golden Horde converted to Islam under Berke Khan (Genghis's grandson, the same Berke who had gone to war with Hülegü over Baghdad). Berke himself converted around 1252. The conversion was finalized as state policy under Öz Beg Khan (also spelled Uzbek; reigned 1313–1341), who made Islam the official religion of the Horde and forced the conversion of the Mongol nobility. Öz Beg's reign was the Horde's economic and political peak. The Moroccan traveler Ibn Battuta (the most-traveled person of the medieval world; he eventually covered 70,000 miles across Africa, the Middle East, India, China, and Spain in a thirty-year career) visited Öz Beg's court in 1332 and left the most detailed eyewitness account of Golden Horde society available anywhere.

The Chagatai Khanate in Central Asia was the most fragile of the four. It controlled the region from the Tian Shan mountains to the Aral Sea, including Transoxiana (the great trade region between the Amu Darya and Syr Darya rivers, containing Samarkand, Bukhara, and other formerly-Khwarezmian cities) and the Tarim Basin to the east. Its population was a mix of Turkic-speaking nomads in the steppe zones and Persian-speaking urban populations in the cities.

The Chagatai khans inherited the political problem of trying to govern both nomadic and urban subjects with the same administrative apparatus, and they spent most of their two centuries failing. The khanate fractured repeatedly, with the western half (Transoxiana — the urban and Islamic-mercantile zone) drifting toward Persian-Islamic culture and the eastern half (Moghulistan — the steppe zone) remaining nomadic and shamanic. Kebek Khan (reigned 1318–1326) attempted economic reforms, introducing a standard silver coin and building a fixed palace at Qarshi. Tarmashirin Khan (TAR-mah-shih-reen, reigned 1331–1334) converted to Islam and tried to enforce Islamic law on his nomadic subjects, which alienated the eastern tribes; he was assassinated, and the khanate split formally into the western Chagatai (Muslim) and Moghulistan (largely non-Muslim) by the 1340s.

The Chagatai Khanate would be the political base from which Timur would emerge a generation later (Chapter 9). Timur claimed Mongol descent through the Barlas tribe and ruled in the name of puppet Chagatai khans. His empire was the immediate political descendant of the Chagatai system, and through the Timurids the Chagatai legacy fed into the eventual Mughal Empire of India.

What held this four-khanate system together economically, even when the khanates were politically at odds, was the Pax Mongolica introduced at the top of this chapter. Its operating mechanisms, in detail, were several.

The Yam relay system (Chapter 4) provided physical infrastructure for travel — stations, fresh horses, food, lodging, all available to anyone holding an imperial paiza tablet. The Yam stations operated across all four khanates with reasonable interoperability; a merchant with the right tablet could travel from China to Persia using Yam infrastructure that was continuously maintained by local Mongol authorities.

Religious tolerance (the Yassa's principle, never abandoned even after various khanates converted to Islam or Buddhism) meant that merchants and missionaries of any faith could operate across the empire with reasonable safety. Christian friars, Muslim qadis, Buddhist monks, and Jewish administrators all moved along the Mongol routes.

Commercial security was enforced by Mongol garrisons against bandits, and merchants' losses were sometimes compensated from Mongol treasuries. The reduction in robbery and arbitrary local tolls made overland trade dramatically cheaper than it had been in the centuries before the conquest.

Standardized currency (paper money in China, silver coinage in the Ilkhanate, the Genoese silver-based commercial system in the Golden Horde) meant that prices could be compared across regions and contracts could be enforced.

Information networks connected merchants and rulers across the empire. A merchant in Tabriz could (and many did) receive reliable news about prices in Beijing within months. A diplomatic missive from the Ilkhan to the Yuan could reach its destination in ninety days. By the standards of any earlier period, this was effectively real-time communication.

The Pax Mongolica is the reason Marco Polo could exist as a phenomenon. It is also the reason that within a decade of the system's collapse, the Black Death would be in Italy.

Cross-civ check: at the height of the Pax Mongolica, around 1300, the Ilkhanate was in trade and diplomatic contact with the Mamluk Sultanate in Egypt (despite intermittent warfare), the Byzantine Empire in Constantinople, the Republic of Venice (and through Venice, the Holy Roman Empire and France), the Delhi Sultanate in India, and the various smaller Christian and Muslim states of the Caucasus and Anatolia. The Yuan was in trade contact with Goryeo Korea, the Kamakura shogunate in Japan (despite the failed invasions, low-grade trade resumed), various Southeast Asian kingdoms, and through Indian Ocean shipping with the Islamic world. The Golden Horde was in active commercial relationship with the Italian city-states, the Hanseatic cities of the Baltic, the Russian principalities, and the Lithuanian Grand Duchy. There has never been another period in pre-modern history when so many distinct civilizations were so simultaneously in active contact along regular trade routes.

Mongol Empire

The Steppe Before Temüjin

Becoming Genghis Khan

The Eurasian Whirlwind

The Sons of Genghis

The Sack of Baghdad and Ayn Jalut

Kublai and the Yuan

The Four Khanates

The Silk Road, the Plague, the Decline

The Long Echo