The Empire That Killed and Connected Most

Any honest account of the Mongols has to hold two things in the same sentence, and most accounts pick one.

The conquests were catastrophic on a scale that is genuinely hard to absorb. Cities were destroyed with their populations. Regional depopulation figures in Persia, Central Asia and northern China are argued over precisely because the plausible range is so wide and the low end is still appalling. The irrigation systems of Khorasan did not recover.

And the century that followed was the most connected Eurasia had ever been, moving technologies, people and ideas at a speed that would not be matched for five hundred years.

Start with how it was done, because the usual explanation is wrong. It was not the bow: the composite bow was centuries old and every steppe people had one. It was not numbers, since the Mongols were almost always outnumbered, often heavily.

It was organisation. Chinggis Khan restructured his army into units of ten, hundred, thousand and ten thousand, deliberately mixing men from different tribes so that loyalty ran to the unit and ultimately to him rather than to a clan. Promotion went to demonstrated competence: Subutai, one of the great commanders of any era, was the son of a blacksmith. Discipline was savage and uniform. Above all, the army could operate in widely separated columns across hundreds of miles and have them converge on a schedule, which requires reliable communication, standard procedure and trusted subordinate command.

That is an administrative achievement wearing military clothes, and it is why the Mongols beat opponents who had the same weapons and more men.

The terror was policy, which is more disturbing than if it had been frenzy. The pattern is consistent: a city that submitted was taxed and left largely intact; a city that resisted and fell was destroyed, and the destruction was publicised. For an army that could not afford long sieges, a reputation that opens gates in advance is worth more than any siege train. It was a calculated instrument, and it worked: many cities surrendered without a fight, which is exactly what it was for.

Against that, set the Pax Mongolica.

With one authority running from Korea to the Black Sea, the yam relay system operating, and merchants actively protected because taxing them was lucrative, the overland routes became passable in a way they had not been for centuries. Marco Polo's journey is an artefact of this; so is the movement of gunpowder, printing and the blast furnace westward, and of Islamic astronomy and medicine eastward.

The Mongols accelerated this deliberately, and the method was monstrous. Skilled craftsmen and scholars were spared during a sack and deported to where they were wanted. Chinese siege engineers appear at Middle Eastern sieges; Persian astronomers appear at Chinese observatories; a Persian minister administers China. It is forced transfer of human capital on an imperial scale, and it is one of the most effective technology-transmission mechanisms in world history.

Their religious policy is similarly instrumental and similarly effective. Clergy of every faith were exempted from taxation, the ruling family included Buddhists, Muslims, Nestorian Christians and shamanists (sometimes in the same household) and the khans staged debates between them for entertainment and information. An empire holding dozens of religions cannot afford to make any of them an enemy, and a privileged priesthood is a cheap ally. This is toleration as administration, not as conscience, and it produced more religious freedom than most contemporaries enjoyed.

And then the structural flaw, which is the one that destroys most conquest empires.

Steppe practice divided an inheritance among sons and chose a great khan by assembly of the princes. That works while there is more to conquer and the assembly still has something to agree about. It fails when the pieces are large enough to stand alone, because every succession becomes a contest between grown men with their own armies, revenues and regional bases.

Every Mongol succession after Ögedei was disputed. By the 1260s the empire had fractured into four khanates that fought each other more readily than anyone else, and the Ilkhanate and the Golden Horde were at war within a generation of their founding.

Rapid conquest, it turns out, is a solvable problem. Transferring authority from one ruler to the next without a civil war is the one that defeats almost everybody, and the Mongols never solved it.

The last thing they moved is the thing nobody planned. The safety of the routes, the volume of traffic and the connection between Central Asian steppe reservoirs and Black Sea ports is the most likely mechanism by which plague reached the Mediterranean in 1347. The century of connection ends with the thing the connection carried.