Genghis Khan was born in north-central Mongolia with the name Temujin (铁木真, 1162–1227). According to the Secret History of the Mongols (蒙古秘密), the oldest surviving literary work in the Mongolian language, Temujin was born with a blood clot in his hand, which according to the Mongolian folklore, meant that he was destined to become a great leader.

Life for the early nomads living in the tribal society of Mongolia was difficult. From a young age, his mother taught him the grim reality of living and the importance of establishing alliances to survive.

At the age of 20, Temujin built an army of more than 20,000 men to unite all the tribes in northeast Asia. He was a military genius — brave and innovative. He employed an extensive network of spies in the enemy camp to understand their motivation and weaknesses. He designed a sophisticated system of signalling by torches and smoke. His soldiers were trained to control war horses using only their legs while leaving their hands free to shoot arrows. He implemented a policy of sharing war spoils with his soldiers rather than the aristocrats, gaining huge followings on the battlefields. He also rewarded bravery and loyalty with wealth and high-level government positions, regardless of family background.

The Khwarazmian (1077–1231) was a Turkish empire that occupied present-day Central Asia, Iran and Afghanistan. Genghis Khan wished to establish a trade relationship with it and sent over a diplomatic mission that included 500-man caravans of gold, silver, silk, and various textiles. On reaching their destination, the governor of Otrar ordered an attack on the caravan, claiming they were a team of spies plotting an attack on the Khwarazmian. When Genghis Khan sent over a second mission to speak to Shah Muhammad, seeking payment for the looted items and the governor be turned over, his envoy was beheaded, and the head was sent back.

With this, Genghis Khan planned one of his most extensive and brutal invasions. From 1219 to 1221, the Mongols swept through the fortifications of Khwarazmian. All those who were not slaughtered immediately were used as human shields during the attack of the next city. Shah Muhammad was captured and killed, and the Khwarazmian Dynasty effectively ended in 1221.

The following two centuries were relatively peaceful. With the Mongol Empire extending from China to Eastern Europe, the Silk Road fell entirely under the control of the Mongols and was once again revived.

Religion was thought of as personal conviction and thus not subject to law or interference by the governing body. Tax exemptions were offered to religious leaders.

It is said that Genghis Khan himself was interested in learning the philosophical and moral lessons from the various religions. His personal consultants included Buddhist and Taoist monks as well as Muslims and Christian missionaries.