In a world fascinated by men like Alexander the Great and Julius Caesar, Genghis Khan is one of history’s greatest and most famous conquerors. No man, before or since, has ever started with so little and gone on to achieve so much. From a noble family but raised in poverty that drove him to the brink of starvation, Genghis Khan rose to control the second-largest empire the world has ever known (the largest being, arguably, the British Empire of the 18th and 19th centuries), and easily the largest empire conquered by a single man. And while many empires disintegrate upon the death of an emperor, like Alexander the Great’s, Genghis Khan’s empire endured and was actually enlarged by his successors, who went on to establish dynasties that in some cases lasted for centuries.

Though history is usually written by the victors, the lack of a particularly strong writing tradition from the Mongols ensured that history was largely written by those who they vanquished. Because of this, their portrayal in the West and the Middle East has been extraordinarily (and in many ways unfairly) negative for centuries, at least until recent revisions to the historical record. The Mongols have long been depicted as wild horse-archers galloping out of the dawn to rape, pillage, murder and enslave, but the Mongol army was a highly sophisticated, minutely organized and incredibly adaptive and innovative institution, as witnessed by the fact that it was successful in conquering enemies who employed completely different weaponry and different styles of fighting, from Chinese armored infantry to Middle Eastern camel cavalry and Western knights and men-at-arms. Likewise, the infrastructure and administrative corps which governed the empire, though largely borrowed from the Chinese, was inventive, practical, and extraordinarily modern and efficient.

Aside from Genghis and his grandson Kublai Khan, the most famous Mongol conqueror was Tamerlane, who dominated Eurasia in the 14th century. He was known by the name Timur in Asia, while the Europeans used the name Tamerlane, which came from the Persian Timur-i-Leng, meaning “Timur the Lame.” This was intended to be an insult referring to crippling injuries he received to his right leg and arm as a young man, probably from arrows, but clearly his injuries did not prevent him from spending much of his lifetime in the saddle.

Tamerlane came from a Turkicized Mongol tribe, the Barlas, which had several constituent sub-clans. A number of original Mongol tribes had migrated west, where the majority of the population was Turkish, and over time, the Mongols blended with the Turks. However, due to his many conquests and his expansive empire, Tamerlane is closely associated with the Mongols today, and while he used Islamic trappings to style himself a restorer of rights and a pious leader, his main aim was to reestablish Genghis Khan’s vast Mongol Empire.

Historians estimate that as many as 40 million lives were lost during the Mongol conquests, and Tamerlane’s campaigns are estimated to have resulted in up to 17 million of those, which would constitute nearly 1 in 20 people across the world at that time. Although these figures must be treated with caution, there is no doubt that Timur and the Mongols massacred almost entire populations in some cities and built towers of severed heads. The massacres were carried out to punish rebels, and in a way, they were theatrical gestures to facilitate submission. Sometimes, survivors were allowed to escape to other cities, where they would explain how pointless it was to resist. Along the way, Timur famously sacked several famous cities, killing an estimated 70,000 at Isfahan, 90,000 in Baghdad, and perhaps 50,000 prisoners massacred during the campaign against the Delhi Sultanate.