MONGOL EMPIRE History of the Great Khans, 1206–1368

The Mongol Empire — A Complete History of the Largest Empire in Human History

The Mongol Empire was the largest contiguous land empire in the history of the world, stretching at its height across Asia and Europe from the Pacific Ocean to the Carpathian Mountains and from the forests of Siberia to the Persian Gulf. Founded in 1206 by Genghis Khan through the unification of the nomadic Mongol tribes on the Mongolian steppe, it grew within a single century into a political entity that ruled over roughly one hundred million people — more than a quarter of the world’s population at the time. Its postal roads, legal codes, religious toleration, and commercial networks transformed Eurasia so completely that historians now refer to the two centuries after the conquest as the Pax Mongolica, a period in which the dangers of long-distance travel were reduced, sometimes dramatically, for everyone from Christian missionaries to Muslim merchants and Buddhist pilgrims.

This page provides a complete overview of the empire: its tribal origins, its explosive expansion under the khans, the systems of law, communication, and trade that held it together, the fraternal civil war that fractured it into four successor khanates, and the long slow decline that followed. The narrative below is woven from the Secret History of the Mongols — the only Mongol history written by Mongols — the chronicles of Persian historians such as Juvaini and Rashid al-Din, the testimony of European travelers like John of Plano Carpini, William of Rubruck, and the Venetian merchants of the Polo family, the Chinese dynastic histories of the Yuan Dynasty, and the modern scholarship that has reshaped our understanding of the empire in the last fifty years.

The Tribal Origins of the Mongols

The people who would become the Mongols were a mosaic of Turkic- and Mongolic-speaking herders who roamed the plateaus of Mongolia centuries before Genghis Khan appeared on the scene. The region’s harsh climate — short summers, brutal winters, and vast tracts of grassland with no agricultural margin for error — produced a society in which wealth was measured not in land but in livestock, and a family’s survival depended on its ability to move, fight, and negotiate alliances. Rivers like the Onon, the Kerulen, the Selenga, and the Orkhon supported dense concentrations of herders during the summer months, while the upland valleys and the forests of the Khentii Mountains provided pasture in winter.

In the centuries before the empire, these steppe peoples lived in a shifting patchwork of tribes and confederations. Some, like the Xiongnu of late antiquity, built confederations that periodically threatened Chinese dynasties and were sometimes appeased by marriage and tribute. Others, like the Khitan, the Tatars, the Kerey, the Naiman, and the Khamag Mongols, left smaller marks on the written record but were equally important in the long chain of events that produced the empire of 1206. The Khitan, after their fall to the Jurchen Jin, had migrated westward and established the Liao dynasty in Central Asia; the Jurchen Jin, who displaced them, were the major southern neighbor of the early Mongols. To the southwest, the Kara-Khitan, the Tangut Western Xia, and the Uighur kingdom of Turfan marked the boundaries of the Chinese-influenced world.

By the late twelfth century, the region was dominated by a number of competing tribal groupings. The Tatars, who lived along the Kerulen and Onon rivers, were among the most powerful. The Kerey and the Onggirat occupied adjacent territories, the Merkit roamed the lake basins to the west of Lake Baikal, the Naiman held the forests and ridges of the Altai and claimed a pedigree from a long line of steppe rulers, the Keraites under the leadership of a prince called Toghrul controlled the upper Orkhon, and the Khamag Mongols — the tribe of Temüjin — occupied a small range in the Khentii Mountains. The political configuration was volatile: alliances shifted, betrayals were common, and the balance of power could change in a single generation.

It was into this politically fragmented world that Temüjin, the future Genghis Khan, was born around 1162, the son of a minor Khamag Mongol chieftain named Yesugei. His birth name was Temüjin, a form of the Mongol word for “iron,” and his family belonged to the Borjigin clan, which claimed descent from Bodonchar, a legendary commoner ancestor who had been born in a cleft in a tree and adopted by the family of a chief. The Borjigin pedigree gave the family a claim to rule, but the fortune of the family was at the moment of Temüjin’s birth modest in the extreme. The Mongols’ rise to world power was not the inevitable consequence of superior numbers or technology; it was the result of a long, contested, often improbable struggle by one particular family in one particular corner of the steppe.

The Rise of Temüjin and the Unification of the Tribes

Temüjin’s path to power was anything but straightforward. When he was about nine years old, his father was poisoned by enemies of the Khamag Mongols, and his family was abandoned by most of its followers. The early life of Genghis Khan was marked by years of poverty, danger, and a brief period of captivity among the Merkit, who had once kidnapped his mother Hoelun in revenge for an earlier raid. From these inauspicious beginnings he slowly built alliances — most importantly with his blood brother Jamukha and with his father’s old friend Toghrul of the Keraites — and gradually accumulated followers of his own.

The Mongol unification was achieved through a combination of personal loyalty, military victory, political marriage, and a willingness to break with the conventions of the steppe. Temüjin defeated the Merkit, forced the submission of the Tayichiud and the Kerey, broke the Tartar (Tatar) confederation in a campaign of deliberate extermination, and finally crushed his old rival Jamukha at the Battle of the Chakirmaut in 1204. On the banks of the Onon River, in the spring of 1206, a kurultai — a great assembly of tribal leaders — proclaimed him “Genghis Khan,” a title whose precise meaning has been debated for centuries but is generally understood to denote something like “oceanic ruler” or “universal sovereign.”

The unification of 1206 was not merely the political consolidation of the Mongol tribes. It was also a sweeping social revolution. Genghis Khan broke the old aristocratic lineages by promoting men of low birth — the smiths, the orphans, the men of the common herd — to positions of command. He reorganized his followers into a new decimal structure of units of ten, a hundred, a thousand, and ten thousand, called tümens, and made the loyalty of a warrior to the khan more important than his loyalty to his clan. He abolished the blood feud, replacing the endless cycle of clan-based vengeance with a system of imperial justice. He gathered children from conquered tribes and raised them as imperial wards, breaking the chain of tribal identity and creating a class of warriors whose only loyalty was to the throne. Within a single generation, Genghis Khan had transformed a loose collection of tribes into a state.

The wars of unification were not limited to the Mongols themselves. The Tangut Western Xia were invaded in 1205, 1207, and 1209, the Jin Dynasty was attacked in 1211, the Qara-Khitan were overthrown in 1218, and the first expedition into the west, against the Merkit and the Kipchak, was launched in 1219. By the time of Genghis Khan’s death, the territory under Mongol control stretched from the Pacific to the Caspian, and the diplomatic letters sent from the Mongol court in Karakorum to the Pope in Rome had become a regular feature of international relations.

One of Genghis Khan’s most consequential reforms was the promulgation of the Yassa code of law, a written body of law that bound the entire Mongol nation. The Yassa was not a comprehensive civil code in the Roman sense; it was a tightly focused set of rules that regulated military service, hunting, hospitality, religious freedom, theft, adultery, and a list of capital crimes. Its central principle was that the security of the army and the unity of the people stood above the interests of any individual or family.

The Yassa was enforced with terrifying consistency. A man who failed to report for a campaign could be executed. A man who harbored a runaway slave or failed to share booty was executed. The killing of another Mongol in a personal dispute could be punished by death rather than by a private blood feud, breaking the cycle of clan-based revenge that had previously torn the steppe apart. Religion was set aside as a matter of state policy: the Mongols were famously tolerant of all faiths and required their subjects to pray in whatever tradition they chose. Later khans codified this religious freedom in imperial edicts, and Persian Muslims, Chinese Buddhists, and European Christians all served the empire in their own way.

The Yassa also established a complex system of taxation, conscription, and military supply. Hunters were required to share their catch with their neighbors; nomads were required to maintain a fixed number of horses, oxen, and sheep; commanders were required to maintain a precise count of their men. A standing army of ten thousand men was quartered at the imperial court, ready to be deployed in any direction at a moment’s notice. The whole machinery of the state was, in essence, a war machine, and the Yassa was the operating manual.

The First Conquests: Western Xia, Jin, and Khwarezm

The unified Mongol state, once created, immediately turned outward. Between 1205 and 1219, the Mongols fought a series of campaigns that, in the space of a single generation, broke the power of the Jin Dynasty in northern China, destroyed the Tangut Western Xia on the upper Yellow River, and shattered the Khwarezmian Empire in Central Asia.

The war against the Jin Dynasty was a long, slow process. The Jin had ruled North China since 1115, and they were a formidable opponent: a Jurchen people with a sophisticated bureaucracy, a large army, and a string of fortified cities along the Great Wall. The Mongols besieged Beijing (then called Zhongdu) in 1215 and captured it after a long campaign; the Jin court withdrew to Kaifeng and continued the war. It was not until 1234, almost a quarter-century after the war began, that the Jin Dynasty was finally destroyed — by Ögedei’s generals, not by Genghis Khan himself.

The war against the Khwarezmian Shah Muhammad II began in 1219, after the Shah treacherously executed two of Genghis Khan’s envoys. The Mongols responded with one of the most devastating campaigns in military history. Within three years, the great cities of Bukhara, Samarkand, Merv, Urgench, Balkh, and Herat had been sacked. The Shah fled and died destitute on a Caspian island; his son Jalal al-Din rallied the remnants of the empire in Afghanistan and inflicted the only major defeat the Mongols would suffer during the conqueror’s lifetime, at the Battle of the Indus in 1221. Genghis Khan chased Jalal al-Din across the Indus but failed to capture him. The campaign in the west, however, had secured the southern flank of the Mongol world and opened the overland trade routes from China to the Caspian.

The Mongol conquest of Khwarezmia was, by any measure, a catastrophe for Central Asian civilization. Merv, the most populous city in the world at the time, was destroyed so completely that it never recovered. Bukhara, the city of Avicenna and al-Biruni, lost most of its population. Samarkand, the pearl of Transoxiana, was depopulated and its great libraries burned. The destruction was so thorough that the modern world has only the dimmest recollection of the cultural richness of pre-Mongol Central Asia. The trade routes that the Mongols would later protect as the Silk Road under Mongol rule were, in the moment of their initial conquest, almost empty of the goods and travelers that had once made them busy.

Ögedei and the Mongol Westward Expansion

When Genghis Khan died in 1227 — probably while on campaign against the Western Xia, in circumstances that remain disputed — the empire he had built passed to his third son Ögedei Khan, whom Genghis had designated as his successor at a great kurultai in 1229. Ögedei was an indulgent, jovial man, but he was also a competent administrator and a steady general, and the empire under his rule continued to expand with terrifying speed.

The campaigns of the late 1230s and early 1240s extended Mongol power into Korea, southern China, India, the Caucasus, Russia, and Eastern Europe. The Korean kingdom of Goryeo became a Mongol vassal after a long war; the Song Dynasty in southern China was invaded but not yet conquered; the Abbasid Caliphate in Baghdad was a target of a coming campaign; the Russian principalities were conquered in three years; and the invasion of Europe proper began in 1236.

By 1240, Mongol armies under Batu Khan, the grandson of Genghis Khan, had overrun the Russian principalities, sacked the city of Vladimir, taken the Black Sea city of Sudak, and defeated the Cumans and the Volga Bulgars. On 9 April 1241, two Mongol armies — one in the north, one in the south — inflicted devastating defeats on the European powers: the Battle of Legnica in Silesia broke a combined Polish-German-Moravian army, while the Battle of Mohi on the Hungarian plain destroyed the army of King Béla IV.

The Mongols then swept through the undefended Hungarian countryside, paused before the walls of Vienna, and withdrew to the Hungarian plain for the winter. Their withdrawal was triggered, not by any European victory, but by the news that Ögedei Khan had died on the Mongolian steppe. By Mongol custom, all princes of the blood were required to attend a kurultai to elect a new great khan, and Batu, the senior prince, refused to leave Europe without the title being settled. The withdrawal of 1242 saved Western Europe from further immediate conquest but did not constitute any kind of Mongol defeat. The Mongols continued to project power into Europe for the rest of the thirteenth century, and Hungary, Poland, and the Crusader states all had to reckon with the Mongol presence for decades afterward.

The Toluid Civil War and the Fracturing of the Empire

The empire created by Genghis Khan was held together by a combination of charisma, custom, and military efficiency, but it had no clearly defined law of succession. By Mongol tradition, the kurultai was required to elect the great khan from among the male descendants of the founder, but there was no agreement on whether the throne should follow primogeniture, fraternal rotation, or some other principle. Tensions between the Toluid branch of the family — the descendants of Tolui, Genghis Khan’s youngest son — and the Ögedeid branch smoldered throughout the 1240s and 1250s, finally erupting into open war.

The Toluid Civil War of 1260 to 1264 was fought primarily on the territory of the empire itself, between the khanate of Persia and the heartland of Mongolia. Its central figures were Kublai Khan, the grandson of Genghis Khan and the most powerful Toluid prince, and his younger brother Hulagu, the conqueror of Baghdad. The war ended in a Toluid victory, the deposition of the Ögedeid khan, and the elevation of Kublai to the position of great khan in 1260 — though the election was disputed by rival branches of the family for decades afterward.

The civil war had consequences beyond the obvious. It confirmed that the empire would remain in the hands of the Toluid branch for the foreseeable future; it encouraged the four major territorial khanates to begin functioning as semi-independent states; and it coincided with the empire’s first major strategic setbacks in the west, most notably the Battle of Ain Jalut in 1260, in which the Mamluk Sultan Baibars halted the Mongol advance into Egypt.

The Four Khanates and the Fracturing of the Empire

By the late thirteenth century, the Mongol Empire was no longer a single state in any meaningful sense. It had divided into four successor khanates, each ruled by a descendant of Genghis Khan and each pursuing its own interests in its own part of the Eurasian world.

The Yuan Dynasty under Kublai Khan ruled China, Mongolia, and Korea. The Ilkhanate, founded by Hulagu, ruled Persia, Mesopotamia, and parts of the Caucasus. The Golden Horde ruled the Russian steppes, the Volga basin, and parts of Central Asia. And the Chagatai Khanate, originally ruling Central Asia, eventually split into eastern and western halves and remained a power in Transoxiana for another century.

The four khanates were connected by shared descent, shared customs, and (sometimes) shared armies, but they were increasingly separated by religion, language, and political interest. The Ilkhanate eventually converted to Islam, becoming an ally of the Egyptian Mamluks against the Golden Horde; the Golden Horde remained largely non-Muslim until the early fourteenth century; the Yuan Dynasty promoted Tibetan Buddhism and Chinese administration; the Chagatai Khanate was a center of Islamic culture by the late thirteenth century. The unity of the steppe was preserved more in theory than in practice, and the empire never recovered the political coherence it had enjoyed under Genghis and Ögedei.

The legacy of the four khanates is still visible in modern Eurasia, though not in the way popular accounts sometimes claim. The name “Iran” — the official designation of the modern state since 1935 — descends from Middle Persian Ērān, “Land of the Aryans” (Aryānām in Old Persian); it predates the Ilkhanate by more than a thousand years and has nothing to do with the Mongol title ilkhan. The name “Hindustan” preserves the Persian form of the older Indian term Sindhu (the Indus River) and was used by Muslim geographers from the 11th century onward. The name “Crimea” preserves a Turkic pronunciation of a Qipchaq tribal name and is older than the Mongol period. The name “Moscow” is etymologically older (a Finno-Ugric root, moskva, meaning “swampy”) and only became a political reality in the 14th century, under the shadow of the Golden Horde. The political geography of the modern world still bears the fingerprints of the khanates, but the linguistic legacy is much thinner than the romantic account suggests.

The Pax Mongolica and the World the Mongols Made

The most enduring legacy of the empire is not military but civilizational. From the late 1220s to the early 1340s — roughly the period from the first Mongol conquests in the west to the collapse of the Pax Mongolica — the overland trade routes of Eurasia were safer, more reliable, and more heavily used than they had been in centuries. Travelers, merchants, missionaries, and diplomats traversed the continent under the protection of Mongol law. A single political framework replaced the patchwork of warring states that had previously made the journey from Paris to Beijing a multi-year gamble.

The consequences for the wider world were enormous. Chinese silk, porcelain, and gunpowder reached the Middle East and Europe. The Black Death, carried by fleas on the trade routes, also moved in the other direction. Italian merchants like the Polo family, the travels of Marco Polo, the diplomatic missions of John of Plano Carpini, the great cartographic projects of the Mongol court, the internationalization of mathematics and astronomy — all of these phenomena can be traced, in some part, to the political unification of Eurasia under the Mongols.

The empire also accelerated the spread of administrative technology. Paper money, the postal system of relays (the yam), the use of census and tax registers, the practice of religious toleration enshrined in written edicts, the integration of foreign specialists into the imperial administration — these innovations, which had been developed in part under the Chinese and Persian empires, were carried across the Eurasian world by the Mongols and became part of the common stock of Eurasian statecraft. The Mongol legal code, the Yassa, was translated into Chinese, Persian, and Russian, and many of its provisions — particularly the prohibitions on interfaith violence, the protection of merchants, the rights of women — survived in regional law long after the empire itself had disappeared.

The religious and intellectual exchange that the empire enabled is also remarkable. European missionaries, including John of Montecorvino, established permanent missions in Beijing. Persian astronomers worked alongside Chinese mathematicians in the observatories of the Yuan court. Muslim physicians, like Rashid al-Din in Tabriz, wrote encyclopedias of world history that drew on Chinese, Indian, Persian, and European sources. The Mongol court at Karakorum was, in a real sense, a cosmopolitan clearing-house for the learning of the pre-modern world.

The Decline and Fall of the Empire

The decline of the Mongol world was a long and complicated process that took almost two centuries to complete. It had less to do with any single military defeat than with the slow erosion of central authority, the rise of regional powers, and the conversion of the khanates to sedentary cultures that were no longer entirely in step with the pastoral traditions of the steppe.

The Yuan Dynasty, which had ruled China since 1279, was expelled in 1368 by the Ming. The Ilkhanate collapsed in 1335 after a long succession crisis. The Chagatai Khanate was partitioned and then absorbed by Timur in the late fourteenth century. The Golden Horde, which had survived longer than its siblings, was finally broken by the rise of Muscovy and the Crimean Khanate in the late fifteenth and sixteenth centuries.

The “Mongol Empire” as a unified entity thus existed for roughly one hundred and sixty years, from the kurultai of 1206 to the last gasp of Yuan authority in 1368. As a cultural and political reality, however, the Mongol world persisted far longer, and the legacy of the empire can still be traced in the languages, political structures, and genetic inheritance of modern Eurasia.

The major causes of the decline have been debated for centuries. Some historians have emphasized environmental factors — the gradual desiccation of the Mongolian steppe, which may have reduced the carrying capacity of the land and weakened the central khanate. Others have emphasized the difficulty of maintaining a single legal and political framework across a continent-sized empire. Still others have pointed to the cultural assimilation of the khanates into their subject populations, which gradually eroded the distinctively Mongol character of the ruling class. All three factors probably contributed, and the eventual fall of the Mongol Empire is best understood as the combined effect of ecological, political, and cultural pressures acting over a long period.

The Mongol Empire in Historical Memory

The reputation of the Mongol Empire has fluctuated dramatically over the centuries. For medieval European chroniclers, the Mongols were the apocalyptic horsemen of the Book of Revelation, the scourge of God, the “Tartars” (a name probably derived from “Tatar” — one of the confederations the Mongols defeated and absorbed — and punning on the Latin Tartarus, the underworld of classical mythology) who had emerged from the mountains of the East to punish Christendom for its sins. For medieval Chinese historians, the Yuan Dynasty was a foreign regime whose legitimacy was always partial and whose fall was inevitable. For Islamic historians like Ibn al-Athir, the Mongols were the wrath of God sent to punish the disunity of the Muslims, and the sack of Baghdad in 1258 was the central catastrophe of the age.

Modern historians have struggled to escape these medieval framings. The “Black Legend” of the Mongols, which emphasized their destructiveness, was dominant in European and Middle Eastern scholarship for centuries. In the eighteenth and nineteenth centuries, the Mongols were sometimes held up as exemplars of enlightened despotism, sometimes as primitive destroyers, and sometimes as the great unifiers of the medieval world. In the twentieth century, the rise of nationalist movements in the successor states — China, Russia, Iran, Turkey — further complicated the picture, as each new state tried to write the Mongol period into its own national narrative.

The most balanced modern view treats the Mongol Empire as a complex historical phenomenon that combined genuine administrative genius with horrific violence, that produced both the Pax Mongolica and the devastation of entire regions, and that left a deep imprint on every society it touched. The empire was, in this view, neither the greatest achievement of human civilization nor its greatest catastrophe, but rather one of the most important transformations in the history of the world, comparable in scale and consequence to the rise of Rome, the spread of Islam, or the European conquest of the Americas.

Sources

This page draws on the following modern scholarship:

  • David Morgan, The Mongols (2nd ed., Oxford: Blackwell, 2007) — the standard one-volume survey in English.
  • Peter Jackson, The Mongols and the West, 1221–1410 (London: Pearson, 2005) — the standard treatment of the western campaigns.
  • Timothy May, The Mongol Conquests in World History: A Life and Death of a World Empire (London: Reaktion, 2012) — the most accessible modern treatment.
  • Janet L. Abu-Lughod, Before European Hegemony: The World System A.D. 1250–1350 (New York: Oxford University Press, 1989) — the Pax Mongolica in world-systems terms.
  • John Man, Genghis Khan: Life, Death and Legacy (London: HarperCollins, 2004) — the most popular recent biography of the founder.

The principal primary sources are: the Secret History of the Mongols (13th c., Mongolian; best modern English edition by Igor de Rachewiltz, 2 vols., Brill, 2004–2013); Juvaini, History of the World Conqueror (13th c., Persian; trans. John Andrew Boyle, Manchester, 1958); Rashid al-Din, Jami’ al-Tawarikh (c. 1300–1311, Persian; partial trans. W. M. Thackston, Harvard, 1998–1999); and the Yuan Shi (the official history of the Yuan Dynasty, compiled 1360–1365).

See Also