After being abandoned by his own tribe and left to live in poverty with just his mother and brothers, it seemed unlikely that Genghis Khan would even survive, let alone flourish. Yet it was less than twenty years later when he became the sole ruler of the Mongol plains, having managed to subdue – through a combination of tactical acumen, military skill, and sheer ruthlessness – the numerous warring tribes of the region.

This was the beginning of the Mongol Empire; the largest unified land empire in the history of the world. By Genghis Khan’s death in 1227, it stretched from the Pacific Ocean to the Caspian Sea, which considering his expansion had begun only twenty years before, was a conquest unprecedented in both speed and scope.

Prior to the Mongol invasion, Eurasia was a divided continent, split between dozens of tribes and empires. This resulted in constant conflict which laid the path open for a strong leader with a unified army to take control. Central Asia was the first to experience the devastation of the Mongol conquests. With a force exceeding 100,000 people, Genghis Khan tore through the disparate territories and brought them under his mastery.

By the end of these first conquests, the Mongol reputation for military prowess and brutality was emphatically established. The obliteration of the Khwarezmid Empire, which covered much of the Middle East, provided the most pertinent example. Genghis Khan had initially tried to ally himself with the Sultan of the empire. Yet the Sultan, perhaps insulted by the superior tone of Genghis’s address, responded by executing the heads of the Khan’s peace delegation.

The result was an invasion that within two years had completely destroyed the Khwarezmid Empire. ‘They came, mined, burnt, killed, plundered and left’, was the description of one refugee. Terror was the Mongols’ most potent weapon; those who resisted in any way were massacred. The governor of the city of Otrar, which had withstood the Mongol onslaught for five months, was brought before Genghis Khan to have molten silver poured into his eyes and ears.

Other cities did not hold as long. The Mongols’ reputation as merciless warriors was well-established, and as Genghis Khan himself declared, ‘walls are as strong as the courage of their defenders’. In the face of a leader who employed tactics such as beheading prisoners who were taller than the wagon wheel they were made to march next to, many people saw their courage fail them.

Samarkand was one such city. Expected to hold out for a year due to its mighty stone walls, it lasted just three days. Even defection was not an option, as the thirty thousand Turkish soldiers guarding the city discovered when they attempted to join the Mongols and turn on Samarkand. Khan had them all executed. Loyalty was an integral part of the Mongol structure.

Genghis Khan also showed shrewdness – skilled men such as artisans and labourers were often spared from slaughter, provided they pledged undying allegiance to him. The Mongols’ attitude of religious tolerance also spared countries from conflict between sects jostling for Mongol patronage.

Though Khan would die in contested circumstances in 1227 – illness or wounds sustained in combat as two of the more plausible possibilities – his work in reorganising and unifying the Mongols, revamping their laws, and establishing their military conduct ensured their expansion could continue until around 1260.

China, the Middle East, Central Europe: none were safe from the Mongol tide. By the time their conquests had finally ground to a halt, as disunity amongst the Mongols themselves created civil war, the Mongol Empire encompassed around a quarter of the world’s population. It had established transcontinental trade routes such as the reconstructed Silk Road, and had brought a degree of relative stability to the regions it controlled.

Yet the cost in lives had also been great. The Mongols, for all their sophistication in empire building and warfare, had not conquered such territory without extreme bloodshed. Some estimates put the number of casualties at thirty million; for others, the death toll was twice that. Asia and Europe had experienced the most brutal of expansions.

Genghis Khan brought the Mongols from obscurity to obscene power. A potent mix of barbarism, martial skill and survivalist cunning, they were a force like nothing the world had ever seen. Despite not being their only leader, Khan is by far their most notorious. Genghis Khan had put the Mongols on the map.