Who Was Genghis Khan? An Outcast Who Built the Largest Land Empire

His name was Temujin, and the main source for his early life is the Secret History of the Mongols, written in Mongol shortly after his death and surviving in a Chinese transcription. His father, a minor chieftain, was poisoned by rivals when the boy was about nine, after which the family was abandoned by its clan and survived on roots and fish, which in a herding society is destitution. He killed a half-brother over food, was captured by a rival clan and escaped, and built his position through an unusual route: not by inheriting followers but by attracting them, cultivating a sworn brotherhood with a boyhood friend who later became his greatest enemy, and taking service under a more powerful khan before displacing him. In 1206, after two decades of steppe warfare, an assembly of the tribes proclaimed him Genghis Khan, usually translated as universal ruler.

The Mongol military system was the most effective of its era and the reasons are organisational rather than mystical:

• •A decimal structure of tens, hundreds, thousands and ten thousands, with units deliberately mixed across tribes to break tribal loyalty and replace it with loyalty to the unit and to him
• •Promotion by demonstrated ability rather than birth, with several of his most senior commanders drawn from enemy tribes or humble origins, including one who had shot his horse from under him in battle and admitted it
• •Every soldier mounted, with several remounts each, giving a strategic mobility no settled army could match, and the composite bow shot from horseback at a gallop
• •Discipline enforced collectively, so that a unit was punished for the failure of an individual, and looting before permission was a capital offence
• •Intelligence gathered systematically in advance through merchants, scouts and envoys, so campaigns began with knowledge of roads, rivals and rivers
• •Rapid absorption of siege technology from conquered peoples, since steppe cavalry could not take walled cities until Chinese and Persian engineers were incorporated, after which they could
• •Deliberate terror as policy, with a city that resisted destroyed comprehensively and the news allowed to travel ahead of the army, which frequently produced surrender without a fight

The direction of expansion was decided partly by provocation. After unifying the steppe he attacked the Tangut state and then the Jin dynasty of northern China, taking its capital in 1215. He then sent a trade mission to the Khwarazmian empire in Central Asia, whose governor executed the merchants, and whose shah executed the envoys sent to complain; the retaliation destroyed one of the wealthiest civilisations of the Islamic world within three years, with the cities of Samarkand, Bukhara, Merv and Nishapur sacked and their irrigation systems wrecked. A detached force under two generals rode around the Caspian, defeated Georgian and Rus forces and returned, having scouted a route that later invasions used. He died in 1227 on campaign against the Tangut, of causes the sources disagree about, and his burial place has never been found, by design.

The administrative record complicates the picture considerably. He promulgated a code of law, the yassa, whose text does not survive but whose provisions are described, covering theft, military discipline, hunting and the treatment of envoys, whose inviolability was absolute. He declared exemption from taxation for religious institutions of every faith, and the empire employed Muslims, Buddhists, Christians, Confucians and Daoists in administration without requiring conversion, which was unusual anywhere at the time. He commissioned a script for Mongol, adapted from Uyghur, giving the language writing for the first time. A relay postal system, the yam, with stations a day's ride apart, allowed messages to cross the empire at remarkable speed and later carried merchants and envoys. The security of the routes across Eurasia under Mongol rule produced an exchange of goods, technology and disease usually called the Pax Mongolica, which is how European travellers including Marco Polo reached China and how printing, gunpowder and the compass moved west.

Estimates of the death toll from the conquests range from a few million to forty million, and the higher figures rest on population declines recorded in Chinese and Persian sources that may reflect displacement, administrative collapse and changed census methods as much as killing. What is not disputed is that specific cities were destroyed with most of their inhabitants, that the agricultural systems of Central Asia and parts of Iran took centuries to recover, and that the psychological impact on the chroniclers who recorded it was total. A study published in 2003 found that a Y-chromosome lineage is carried by around eight percent of men across a large area of Asia, which the authors attributed to his patriline, a figure often quoted loosely as sixteen million descendants and which has been questioned since. His reputation differs sharply by geography: a founding national figure in Mongolia, where his image is on the currency and the airport, a catastrophe in Persian and much of Islamic historiography, and in China a complicated figure claimed as the founder of a dynasty by a state that was conquered.

Temujin was left destitute as a child, built a following by attracting rather than inheriting one, and was proclaimed universal ruler in 1206 after unifying the steppe tribes. His army worked through a decimal structure that broke tribal loyalty, promotion by ability, total mobility, harsh collective discipline, systematic intelligence, absorbed siege technology and terror used deliberately to induce surrender. The empire codified law, exempted all religions from tax, created a script for Mongol and secured the overland routes, at a human cost that is enormous and genuinely disputed in scale.