The Central Asian plateau (north of China) around the time of Temüjin was divided into several tribes or confederations in the early 1200s, among them Naimans, Merkits, Uyghurs, Tatars, Mongols, Keraits that were all prominent in their own right and often unfriendly toward each other as evidenced by random raids, revenges, and plundering.
Temüjin began his slow ascent to power by offering himself as an ally (or, according to others sources, a vassal) to his father's anda (sworn brother or blood brother) Toghrul, who was Khan of the Kerait, and is better known by the Chinese title Ong Khan (or "Wang Khan"), which the Jin Empire granted him in 1197. This relationship was first reinforced when Börte was captured by the Merkits; it was to Toghrul that Temüjin 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 (ruler) 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, Temüjin and Jamuka.Temüjin also became blood brother (anda) with Jamuka, and they vowed to remain eternally faithful earlier.
The main opponents of the Mongol confederation (traditionally the "Mongols") around 1200 were the Naimans to the west, the Merkits to the north, Tanguts to the south, the Jin and Tatars to the east. By 1190, Temüjin, his followers and advisors united the smaller Mongol confederation only. In his rule and his conquest of rival tribes, Temüjin broke with Mongol tradition in a few crucial ways. He delegated authority based on merit and loyalty, rather than family ties. As an incentive for absolute obedience and following his rule of law, the Yassa code, Temüjin promised civilians and soldiers wealth from future possible war spoils. As he defeated rival tribes, he didn't drive away enemy soldiers and abandon the rest. Instead, he took the conquered tribe under his protection and integrated its members into his own tribe. He would even have his mother adopt orphans from the conquered tribe, bringing them into his family. These political innovations inspired great loyalty among the conquered people, making Temüjin stronger with each victory.
Toghrul's (Wang Khan) son Senggum was jealous of Temüjin's growing power, and his affinity with his father. He allegedly planned to assassinate Temüjin. Toghrul, though allegedly saved on multiple occasions by Temüjin, gave in to his son and became uncooperative with Temüjin. Temüjin learned of Senggum's intentions and eventually defeated him and his loyalists. One of the later ruptures between Toghrul and Temüjin was Toghrul's refusal to give his daughter in marriage to Jochi, the eldest son of Temüjin, a sign of disrespect in the Mongolian culture. This act led to the split between both factions, and was a prelude to war. Toghrul...