Born simply Temujin in 1167 AD, Chingghis Khan, his mother and siblings were abandoned by their clan after his father, a clan chieftain, was poisoned. (Chingghis is the Mongolian form of his name--Jenghis or Genghis as it is spelled in English comes from the Persian form.) Although a young boy at the time, Temujin promised to take revenge. The half dozen major Mongol clans, the Buryats, Oirats, Nalmans, Keyerits, Merkits and Khitan, were constantly at war with each other, but this usually consisted of back-and-forth raiding. Temujin soon proved his military skills in this raiding and attracted a loyal following, but could not gain a decisive advantage over his rivals. After more than a dozen years, Temujin had begun to use a new, more ruthless strategy where he sought decisive victories. In structuring his army, he integrated soldiers from different tribes, thus inspiring loyalty to the Mongol army as a whole rather than to a specific clan. He gave his enemies one simple choice: surrender and be enslaved, or die. By 1206, Temujin's military genius had defeated all competing clans, and he was proclaimed Chingghis Khan, meaning "ruler of the universe".

The Mongol army was based on lightly armoured horse archers. Under a quilted jacket or water-proofed leather jerkin, Mongol warriors wore a silk shirt. Even if an arrow penetrated their armour, unlike other cloth, the silk shirt would not tear but would wrap around the arrow head. This made it easier to remove the arrow and reduced the chance of infection. With cotton, wool or other cloth, bits of torn material would be driven into a wound making a dangerous infection likely.

Chingghis Khan was also a skilled administrator. Mongol society was based on the army. While often seen as the typical barbarians, the Mongols were highly organized. The army was based on units of ten. For example, our word "horde" comes from the Mongol ordu. An ordu was an army of 10,000 men divided into ten regiments, each regiment with 1000 men (divided into ten companies each with 100 warriors). At the time of his death in 1227, the Mongolian Empire, the largest yet seen in the world, extended from Hungary across Asia to Korea, and from Siberia to Tibet.

While many cities had been devastated, Mongol rule brought relative peace to Asia, leaving China accessible to foreign visitors, such as the Italian Marco Polo. Native arts flourished, including calligraphy, painting and literature. Chingghis Khan, to hold his vast empire together, created an efficient horse and rider communication system similar to the pony express, and introduced the first written Mongol language.