Why were the Mongol horse archers so hard to beat?

They combined speed, a weapon that could be shot from a galloping horse, and strict discipline. Each Mongol soldier typically kept three or four horses and swapped between them, which let the army travel at high speed for days without wearing out the animals. The main weapon was a composite bow of laminated horn, wood and sinew, small enough to use from horseback yet powerful: a Mongol archer could shoot over 200 metres, with aimed shots at around 150 or 175 metres.

On top of that came organisation. Mongol armies were almost always outnumbered, and the total strength available in Genghis's lifetime was likely only 50,000 to 75,000 soldiers. What made up for it, historians say, was cohesion and unity. Officers answered for the training of their men, comrades had to protect one another, and nobody was allowed to flee or loot without permission. Even a distinctive haircut helped: its uniqueness discouraged desertion.

The tactics were built on the steppe. The famous feigned retreat could last days, drawing enemies after the Mongols until they were tired and the Mongols could turn on a battlefield of their choosing. Armies advanced in several columns behind scouting screens tens or hundreds of kilometres wide, and they usually started campaigns in winter, because they favoured fighting in cold weather.

Finally there was fear. The Mongols spread news of their massacres, made their armies look bigger with dummies on spare horses and extra campfires, and tried to turn rivals against one another. When their enemies had walled cities, they learned: they were at first poor at sieges, but quickly added Muslim and Chinese siege engineers to their armies.