Temujin was born around 1162 in a Mongol tribe near Mount Burkhan Khaldun and the Onon and Kherlen rivers, not far from the city of Urga. He was the third-eldest son of his father Yesukhei, a minor tribal chief of the Kiyad and a vassal of Ong Khan of the Kerait tribe, and the eldest son of his mother Hoelun. The name also suggests that they may have descended from a family of blacksmiths.
The Central Asian plateau north of China around the time of Temujin was divided into several tribes or confederations, among them Naimans, Merkites, Uighurs, Tatars, Mongols and Keraites that were all prominent in their own right and often unfriendly toward each other.
Temujin began his slow ascent to power by offering himself as an ally to his father's anda (sworn brother or blood brother) Toghrul, who was Khan of the Keraites, and better known by the Chinese title Ong Khan, which Jin China had granted him in 1197. This relationship was first reinforced when Temujin's wife Börte was captured by the Merkites; it was to Toghrul that Temujin turned for support. In response, Toghrul offered his vassal 20,000 of his Kerait warriors and suggested that he also involve his childhood friend Jamuka, who had himself become Khan of his own tribe, the Jadaran. Although the campaign was successful and led to the recapture of Börte and utter defeat of the Merkits, it also paved the way for the split between the childhood friends, Temujin and Jamuka.
The main opponents of the Mongols around 1200 were the Naimans to the west, the Merkites to the north, Tangutes to the south, the Jin and Tatars to the east. By 1190, Temujin, his followers and advisors united the smaller Mongol confederation only. As an incentive for absolute obedience and following his rule of law, the Yassa code, Temujin promised civilians and soldiers a wealth from future possible war spoils.
Toghrul's son Senggum was jealous of Temujin's growing power, and his affinity with his father. He allegedly planned to assassinate Temujin. Toghrul, though allegedly saved on multiple occasions by Temujin, gave in to his son and became uncooperative with Temujin. Temujin learned of Senggum's intentions and eventually defeated him and his loyalists. One of the later ruptures between Toghrul and Temujin was Toghrul's refusal to give his daughter in marriage to Jochi, the eldest son of Temujin, a sign of disrespect in the Mongolian culture. This act led to the split between both factions, and was a prelude to war. Toghrul allied himself with Jamuka, who already opposed Temujin's forces; however the internal dispute between Toghrul and Jamuka, plus the desertion of a number of their allies to Temujin, led to Toghrul's defeat. Jamuka escaped during the conflict. This defeat was a catalyst for the fall and eventual dissemination of the Kerait tribe.
The next direct threat to Temujin was the Naimans, with whom Jamuka and his followers took refuge. The Naimans did not surrender, although enough sectors again voluntarily sided with Temujin.
In 1200, Temujin died by an accident. Since his four sons (Jochi, Chagatai, Ogadai, and Tolui) were still too young (they were between 10 and 15 years old now), he had no clear successor. Enemies of Temujin, like his former friend and blood brother Jamukha Gurkhan, some of the clans and people he defeated and some people who were simply ambitious tried to use the situation, and the people Temujin already united fell apart. Some of Temujin's "Dogs of war" (Subodai, Chilaun, Jelme and Borchu) and his family were still willing to fight to preserve his heritage, but for the beginning his dream had suffered a setback. The following years were filled by infighting between the various steppe tribes and people, with too many battles and changing alliances to mention them.