Appearance
7.6 — The Mongols
In 1219 a caravan of merchants under Mongol protection arrived at Otrar, a city of the Khwarezmian empire in Central Asia. The governor accused them of spying and had them killed. Genghis Khan sent envoys demanding the governor be handed over. The Shah had the chief envoy executed and the others sent back with their beards burned off.
The Mongol response destroyed the Khwarezmian empire, one of the largest states in the Islamic world, within three years. Cities that had stood for a thousand years were emptied. Merv, Nishapur, Herat, Bukhara and Samarkand were sacked, several with the general slaughter of their populations.
The lesson the Mongols intended was learned across Eurasia, which was the point.
Temujin
Born around 1162 on the Mongolian steppe. His father, a minor chief, was poisoned by rivals when Temujin was about nine, and the clan abandoned the family. He grew up in poverty, was captured and enslaved by a rival clan and escaped, and killed his own half-brother in a dispute over food.
What he then did was reorganise steppe society.
He broke the tribes. Instead of units based on kinship, he organised his people into military decimal units — tens, hundreds, thousands, ten thousands — mixing men from different tribes deliberately, so that loyalty attached to the unit and to him rather than to the clan. Deserting your unit was punished by death for the whole unit.
He promoted on merit. His two greatest generals, Subutai and Jebe, were of humble origin — Subutai was a blacksmith's son. In a steppe world where command followed birth, this was a decisive advantage.
He spared and recruited the defeated. Enemy soldiers who submitted were absorbed into the army. A conquered people became a resource rather than a liability.
He forbade the traditional free-for-all looting and required plunder to be pooled and distributed by rank, which removed the incentive for units to break off mid-battle.
And he issued a law code, the Yassa, which does not survive in full and which is known to have covered military discipline, theft, and — significantly — religious tolerance and the exemption of clergy of all religions from taxation.
In 1206 an assembly of the united tribes proclaimed him Genghis Khan, usually translated as universal or oceanic ruler.
Why the army could not be stopped
Six factors, and it is the combination that matters.
Mobility. Every man had multiple horses — commonly three to five — and rotated them, so the army moved at a rate no settled force could match. Mongol armies covered distances that opponents believed impossible and repeatedly arrived where nobody expected.
Logistics. The army carried dried meat and curd, and could live off mare's milk and blood in extremity. It did not need supply trains, which is what limits every other pre-modern army's range and speed.
The composite bow. Layers of wood, horn and sinew, glued and bent against its natural curve, storing far more energy than a self bow of the same length. Short enough to shoot from horseback, with a draw weight comparable to an English longbow, and shot at the gallop.
Discipline and signals. Units manoeuvred by flag, drum and later flaming arrow signals, executing coordinated movements over kilometres — including the feigned retreat, which requires a formation to run away convincingly and then reform and turn. This is the manoeuvre that destroyed European heavy cavalry repeatedly, because a knight who pursues has broken his formation.
Intelligence. Merchants, spies and scouts were used systematically. Campaigns were preceded by reconnaissance and by deliberate cultivation of internal divisions in the target.
And adaptation. The Mongols had no siege capability initially. So they took Chinese and then Persian engineers and used them. By the 1250s they were deploying counterweight trebuchets and gunpowder devices, and Chinese engineers built the siege machines that took Baghdad while Persian engineers built those used in China.
The terror, honestly assessed
The Mongols used massacre as policy and said so.
The method: a city that surrendered on first demand was taxed and left largely intact. A city that resisted and was then taken was destroyed and its population killed, with craftsmen spared and deported. The point was to make surrender obviously the better option, and it worked — many cities opened their gates.
The figures in the sources are enormous and unreliable. Persian and Arabic chroniclers give numbers for single cities — 700,000 at Merv, 1.7 million at Nishapur — that exceed any plausible population. Deliberate exaggeration served both sides: it magnified Mongol terror, which was useful to them, and it magnified the catastrophe for the chroniclers' own communities.
What is reliable is the archaeology and the demography. Persia and Central Asia show a genuine and long-lasting collapse — cities not reoccupied, irrigation systems that had taken centuries to build destroyed and never repaired. The destruction of the qanat underground irrigation networks of Iran and Iraq is the single most consequential piece, because agriculture in those regions never recovered its former extent.
Total deaths across the conquests are estimated at tens of millions, which on any reckoning makes it one of the most destructive episodes in history relative to world population.
And the Baghdad sack of 1258 ended the Abbasid caliphate. The libraries were destroyed — the story that the Tigris ran black with ink is a literary image and the loss of the accumulated manuscript collections of five centuries is not. Chapter 7.2 identified this as a principal cause of the end of the Islamic golden age.
The extent, and the two failures
China. Northern China was taken from the Jin; the Southern Song held out for decades behind river defences and fortified cities and fell in 1279. Kublai Khan founded the Yuan dynasty and ruled China as a Chinese emperor, moving the capital to what is now Beijing.
Persia and Mesopotamia under the Ilkhanate.
Russia. The Rus principalities were conquered in the 1230s and 40s and held for around 240 years under the Golden Horde, which ruled indirectly through tribute and licences to the Russian princes. Moscow rose specifically as the Horde's preferred tax collector, which is how a minor town became the centre of Russia.
Europe. In 1241 Subutai destroyed a Polish-German army at Legnica and a Hungarian army at Mohi within two days of each other, using coordinated columns hundreds of kilometres apart. Central Europe was open. And then the Great Khan Ögedei died, and the commanders withdrew to attend the succession assembly. They never returned in force. Europe was saved by a death in Mongolia.
Japan was attempted twice, in 1274 and 1281, and both fleets were wrecked by storms — the kamikaze, divine wind. The 1281 fleet was one of the largest naval invasions ever attempted before the twentieth century. Marine archaeology has found evidence that many of the ships were hastily built river vessels unsuited to open sea, which supplements the weather explanation.
Egypt stopped them at Ain Jalut in 1260, where the Mamluks — a state ruled by a self-perpetuating military caste of slave origin — defeated a Mongol force. The Mongol army was smaller than usual because the main force had withdrawn for another succession crisis, which is the third time succession disrupted the empire and points at its central structural flaw.
The Pax Mongolica
Once the killing stopped, the empire produced the safest and most connected Eurasia had ever been.
A single authority ran from Korea to the Black Sea. The saying preserved in the sources is that a virgin with a pot of gold could ride across the empire unmolested — propaganda, and pointing at a real fact.
The yam was a relay post system with stations at intervals of about 40 kilometres, fresh horses, and messengers who could cover 300 kilometres a day. Marco Polo described it in detail and Europeans did not believe him.
Trade and travel flourished. Marco Polo travelled to Kublai's court and claimed to have served him for years; the Franciscan William of Rubruck was sent as an envoy and left a shrewd, sceptical account; Rabban Bar Sauma, a Turkic Christian monk from Beijing, travelled the other way and met the kings of England and France and the Pope.
Technology moved. Gunpowder, printing and the compass all travelled west in this period (Chapter 8.3), and Persian astronomy and medicine travelled east — the Maragha observatory in Persia and the Beijing observatory exchanged personnel and instruments.
Religious tolerance was policy. Mongol rulers patronised Buddhists, Muslims, Christians and Daoists, and held debates between them. Different branches of the family converted to different religions — the Ilkhanate and the Golden Horde to Islam, the Yuan toward Buddhism.
And administration was delegated. The Mongols were a small population ruling enormous settled societies, so they used Chinese, Persian, Uyghur and Muslim administrators, and adopted local systems wholesale.
And the plague
The connection is direct. The plague bacterium is endemic in rodent populations in Central Asia. The trade and troop movements the Mongols enabled carried it west.
The transmission point usually cited is the siege of Caffa in the Crimea in 1346, where a Genoese trading colony was besieged by Golden Horde forces, plague broke out in the besieging army, and — according to a single contemporary account by a Genoese notary — corpses were catapulted over the walls. Whether that specific act transmitted the disease is doubted; the ships that fled Caffa for Italy carried it either way.
Chapter 7.7 is what happened next.
Why it fell apart
Succession, above all. The Mongols had no fixed rule; each Great Khan's death required an assembly, which meant campaigns halted and factions formed. Three separate withdrawals from active campaigns — from Europe in 1241, and twice in the Middle East — were caused by succession crises.
Division into four khanates — Yuan China, the Ilkhanate, the Chagatai Khanate and the Golden Horde — which then fought each other.
And absorption. Mongol rulers adopted the culture, religion and administration of the peoples they ruled — Chinese in the east, Persian and Islamic in the west — and within a few generations the distinct Mongol identity of the ruling elite had largely dissolved. This is the recurring fate of steppe conquerors of settled civilisations (Chapter 5.6), and it is the deepest reason such empires do not persist.
Where this shows up in your life
Russia's political development was shaped by 240 years under the Horde, and the argument about how much — whether Russian autocracy inherited a Mongol model or would have developed anyway — is one of the oldest in Russian historiography.
Moscow, Beijing as a capital, and the current borders of several Central Asian states all trace to Mongol arrangements.
Genetic studies have found a Y-chromosome lineage present in a very large number of men across Asia, dated to around the right period and geographically centred on Mongolia, which has been widely reported as descent from Genghis Khan personally. The lineage is real; the specific attribution is an inference and is not proven.
And the general lesson is about connection. The Mongols destroyed on a scale nothing had matched, and then connected Eurasia more thoroughly than it had ever been connected, and the connection carried both prosperity and a pandemic. Chapter 5.7 said that a connected world shares its diseases; Chapter 12.8 says it about a connected financial system. The Mongol century is where the trade-off is at its starkest.
What the next page covers
Between 1347 and 1351 somewhere between a third and a half of Europe's population died. Chapter 7.7 covers the Black Death — what the disease actually is and how it spreads, why the mortality was so high, what people believed was causing it and what they did about it, the persecutions that followed, and the argument that the labour shortage it created broke serfdom and set European wages on a path that mattered enormously four centuries later.