Genghis Khan

He was not born a conqueror. He was born Temüjin, around 1162, on the cold, open grassland between modern Mongolia and Siberia. His people were nomadic herders — tribes of riders who moved their tents across a vast sea of grass, following their animals and, often, raiding one another. His father, Yesügei, was a clan chief, and for a few early years the boy's life was secure.

Then it collapsed. When Temüjin was about nine, a rival tribe, the Tatars, poisoned his father at a feast. With Yesügei dead, his own clan abandoned the family, judging a widow and her small children too weak to be worth feeding. Temüjin's mother kept them alive on roots, fish and small game while the boy grew up hard, fast and unforgiving. As a teenager he was captured by a former ally and held as a slave with a wooden collar around his neck — and he escaped, slipping away at night and hiding in a river until his captors gave up the search.

What he understood, earlier than most, was that on the steppe a lone man was nothing. Survival meant loyalty, and loyalty had to be built. Slowly, shrewdly, he began to forge alliances — with his father's old sworn friends, with a powerful neighbouring chief — and to draw warriors to him not by blood but by reward and trust. Men who followed him and fought well were promoted, whatever family they came from. Men who betrayed him did not get a second chance.

For over twenty years Temüjin fought the other peoples of the steppe — the Tatars, the Kereyids, the Naimans, the Merkids — sometimes as an ally, often as an enemy. He won not only with courage but with intelligence. He reorganised his fighters into neat units of tens, hundreds and thousands, so that orders could pass quickly and cleanly. He used spies, surprise and, again and again, the famous feigned retreat: his horsemen would pretend to flee in panic, drawing the enemy into a wild chase, then suddenly turn and destroy them on open ground of his own choosing.

By 1206 he had done what no one before him had managed: he had united the warring tribes of Mongolia under a single command. At a great assembly by the river, the chiefs proclaimed him their supreme leader and gave him a new name — Genghis Khan, meaning something like "universal ruler." To hold this fragile new nation together he set down a code of laws known as the Yassa. It demanded absolute loyalty, banned the kidnapping of women and the stealing of animals, protected envoys and merchants, and — strikingly for the age — granted freedom of religion across his lands.

Then he looked outward. His cavalry — tough, fast, able to live for days on dried meat and mare's milk — could cover ground no settled army could match. He turned south against the rich kingdoms of China, and west toward central Asia, and the conquest began in earnest.

One moment, more than any other, shows what he became. In 1218 Genghis Khan sent a peaceful trade caravan and, later, envoys to the wealthy Khwarazmian Empire in central Asia. The local governor had the merchants killed as spies; the Shah then beheaded the chief envoy and sent his head back. Genghis Khan's reply was total. His armies fell on the empire and, within a few years, erased it — sacking its great cities one after another in long, brutal sieges, and killing on a scale that is still hard to imagine. Whole cities that resisted were destroyed so completely that they never recovered.

And yet that is only half the story. By the time he died in 1227 — falling ill, most accounts say, on campaign — he ruled the largest land empire ever assembled, stretching from the Pacific coast toward the Caspian Sea. His sons and grandsons pushed it further still. Across this vast space the Mongols enforced a fierce peace, sometimes called the Pax Mongolica. For the first time, a merchant could carry goods the whole length of the Silk Road in relative safety, guarded by Mongol patrols and supplied by a network of relay stations. Ideas, goods, inventions and even diseases travelled between East and West as never before.

His personal legacy is just as vast. He left descendants beyond counting — by one famous genetic study, millions of men alive today may carry his line, though scholars now argue over the true number. To some he is a national hero and founding father; to others, the author of one of history's great catastrophes. He was almost certainly both: the abandoned boy who became the most ruthless and the most consequential conqueror the world has known.