Temujin, the son of a Mongol chieftain, is born. He marries Borte, his first wife, but she is kidnapped by the Merkits, a rival tribe. Temujin unites rival tribes under his rule to free Borte. After defeating the Merkits and freeing her, he goes on to defeat other tribes. He institutes policies to support his soldiers rather than the aristocrats, but this brings him into conflict with his uncles, who claim the throne.

Temujin becomes the ruler of the Ikh Mongol Uls at the kurultai (the general assembly of the tribes) and assumes the name Genghis Khan, which means "universal leader."

Khan, pressured by both spiritual needs and scarcity of food, attacks the kingdom of Xi Xia, and after two years he forces it to surrender. Lured by rich rice fields, Genghis Khan then attacks Northern China under the Jin Dynasty, starting a war that lasts twenty years.

In 1219, Khan leads an army of 200,000 Mongol soldiers against the Khwarzin Dynasty in response to the Khwarzin leader's refusal to cooperate. The Mongols brutally invade every city they came across, killing or enslaving everyone they came across.