For one month, his army plundered, burnt and raped. A year later, visiting foreign ambassadors described the streets as "slippery with human fat." They also recorded that beyond the walls stood an entire mountain of bones.

Genghis Khan's fearsome reputation grew from the destruction and carnage he practised in Beijing. But what he now created at Karakorum in central Mongolia revealed an entirely different nature.

Genghis Khan wanted Karakorum(喀拉昆侖) to be a great trading and cultural center. Here, in stark contrast to his nomadic origins, he began to establish a permanent capital. And he wanted his people to benefit from his conquests.

"My people were as numerous as the trees in the forest here. I wanted them to feed on tender meat here, live in beautiful tents and pasture their horses on rich soil."

To achieve this, he imported knowledge; he learnt the technology of the Chinese military. He established a medical corps trained by Chinese physicians. He ordered his followers to create a record of all his rules and all his judgments. It was forbidden for any man to own a Mongol slave. And each tribe was given its own grazing grounds. It was the beginning of a legal system.

The Mongols could neither read nor write. But Genghis Khan understood the power of the written word. Above all, he wanted his legacy recorded.

carnage: massacre, mass murder, holocaust

grazing: pastureland, pasture, field or plot of ground where livestock are grazed