Genghis Khan kills all the prominent males of the Tayichiud lineage (who were the leading tribe of the Mongols until Temujin's rise), and takes their people as his own. Though, this doesn't count those Tayichiud males who became his companions, such as Jebe. This is how it happened.

Old Sirgeitei of Nichugut Barin and his sons Alak and Naya corner their Khan Tarkutai Kiriltuk, chief of the Tayichiud, and leader of the Mongols, in a forest. They capture him and put him in a cart, since he can't ride a horse (was he injured?).

Tarkutai's sons spot him and the Nichugut Barins, and catch up to them. As they're closing on them, Old Sirgeitei gets into the cart and mounts Tarkutai with a knife in his hand. Sirgeitei tells Tarkutai Kiriltuk, "they're going to kill anyone who dared to touch the Khan [Tarkutai]. So, I'm going to make sure I take you with me. If I die, you die." Tarkutai calls his family off, telling him to stop the attack, since Sirgeitei has him hostage. Tarkutai reassures his fam by saying he trained Temujin when Temujin was a kid, so surely, Temujin wouldn't kill him. Maybe they could've revealed all this without the back-and-forth threats.

So Old Sirgeitei, Alak, and Naya continue on their mission, but as they get closer to Genghis Khan, they worry that Genghis might kill them for being disloyal to their chief. How come they didn't realize this sooner? So they set Tarkutai Kiriltuk free, and offer their allegiance to Genghis Khan.

Genghis Khan confirms what they thought, and told them he would've killed them if they had brought their lord to him. As it is, he commends them for their honor and accepts them into his service.

Jaka Gambu of the Kereyit joins Genghis as a messmate. It's about then that the Merkit attack them, and Genghis, Jaka Gambu, and others push them back. After that, Jaka Gambu gets two other groups Kereyit to join Genghis. If you recall, Ong Khan is also Kereyit, and became Temujin's father's sworn brother when Temujin's father helped him. Ong Khan became outcast when he killed his brothers and uncles, so Temujin's father's help was a big deal. When you support people who everyone else has rejected, they're more likely to be extremely loyal to you, if they're aware of their social situation. So he basically became Temujin's father after Temujin's father died.

Ong Khan was hunting one of his many younger brothers, who found a powerful Khan as an ally. Since Ong Khan was considered a rebel in that area, he went from place to place (including passing through Uighur and Tangut areas), surviving on milk from a few goats, as well as camel's blood, which is something nomads do in times of food scarcity- drink blood from their mounts.

So when Ong Khan got to Genghis, Genghis raised taxes to restore him to his position.

The younger brothers of Ong Khan get together and review Ong Khan's life. They point out that he got kidnapped several times by different tribes, went native several times, and escaped several times. They figure this has made him bitter (given him a "bad liver"). They point out that he's basically a poor fuck, and only survives because his son (Temujin) is powerful.

Under Temujin, Ong Khan technically rules all his brothers, so when he finds out about their plotting, he detains them. He has them brought to him in chains, spits at them, basically calls them ungrateful shits, and releases them. Everyone else in the tent spits on them.

After the winter of 1201-1202, Genghis Khan goes after some Tartars. The Tartars have apparently been raiding many other tribes for generations. He tells everyone that they're not going to stop to loot anything when they're hunting the Tartars. They will only loot after all the enemy is dead, and then they can share all the loot together. They set a rally point in case they have to retreat, and he threatens to kill anyone who does not meet them at the rally point if they retreat.

They beat the Tartars in battle, chase them against a river where all the non-warriors are, and kill many of the warriors (including some important figures), and then loot all their people.

Three people had stopped to loot before all the Tartar warriors were killed, so Genghis sends Jebe and Kublai to confiscate all their loot.

This done, Genghis gathers all the warriors in one tent, to decide the fate of the Tartars. They decide to kill all the men who are taller than a linchpin of a cart and enslave the women and children. As they're coming out of the tent, one of the Tartar leaders asks Belgutei about the decision, and he tells him the truth. So the Tartars run, construct a barricade, and fight to the last man. They try to take at least one of Genghis' men down with them as they die. So Genghis takes a lot of casualties, and it is a difficult extermination.

After that, Genghis Khan decides that Belgutei shouldn't be in the tent during council meetings anymore. Instead, Genghis Khan gives Belgutei the job of judging everyone else's disputes and handing out appropriate punishments (for things like theft) while the warriors are in council. See how Temujin doesn't quite punish Belgutei, but gives him a job that he is better suited to.

Genghis Khan takes one of the Tartar chief's daughters (Yisugen Katun) as his wife. She says she hopes he will find her worthy, but her older sister is probably better suited to be a ruler's wife. She wonders out loud about where her older sister might have got to. She was recently married, but given that the bridegroom was a Tatar, he is probably dead. Genghis says that's fine, but will she accept losing her place as his higher-positioned wife if she finds her older sister? She says yes.

Genghis Khan's men find the older sister and the bridegroom escaping to the woods. The bridegroom runs away, but the Tartar princess Yisui Katun is captured. Genghis confirms that Yisui is indeed a better ruler's wife, and Yisugen gives up her seat to take a lower position. Genghis gives Yisui a position as one of his main wives.

One day Yisui, Temujin, and Yesugen are chilling and drinking when Yisui sighs deeply. Genghis Khan notices this deep sigh, and gets his men to get everyone in the camp together, and to get all his men to get all their people to be gathered in groups. In this way, they find one man who doesn't have a group. He turns out to be tall and handsome, so they question him. He's Yisui's husband, and it's true he ran away, but he figures everything is quiet now and so it would be alright for him to come back. Genghis wonders if this man is a spy, and says they already killed every Tartar man taller than a linch pin of a cart, why is it so hard to kill one more. So they kill him.

In the same year that Genghis was doing all this with the Tartars, Ong Khan goes after the Merkit.

Ong Khan chases Toktoah Bekti to a low lying area, where he kills his son and takes two of his daughters as his wives. He also gets some good loot, but gives none of it to Genghis Khan.

Genghis joins Ong Khan, and together they go to Sokok River, where Buyiruk Khan is camped. Buyiruk manages to escape. One of Genghis's patrols catches one of Buyiruk's patrols when their leader's saddle strap breaks, as he was trying to go uphill. They figure (maybe from intel from the captured patrol?) that Buyiruk is going to be at Redhead Lake, so they head him off and ambush him there, where they kill Buyiruk. On their way back, a well-known Naiman warrior, Kokseu Sabraq, sets up to meet them in battle. They meet him, but both sides decide to fight the day after, since it is near sunset.

At night, Ong Khan lights his campfires, but sneaks off along the river. In the night, he meets Jamukha, who notes that he likes to stay in one place, while Temujin is more migratory, and jokes about Temujin wanting to defeat the Naiman on his own. Gurin Baatur of the Ubchiritei asks Jamukha how he can talk so much shit about his own bro.

In the morning, Genghis gets up and, noting that Ong Khan is nowhere to be seen, remarks that he and his men are being treated like burnt offerings, to be sacrificed. Genghis crosses the river and goes uphill to another steppe.

Kokseu Sabraq pursues Ong Khan, and manages to capture Ong Khan's son's wife, as well as half of that son's people. Some Merkit leave Ong Khan's entourage, and go back to their father.

Ong Khan asks Genghis Khan, as his son, to send him his four horses- that is, Boorsu, Mukali, Borokul, and Sila'un Baatur. Ong Khan's son (whose wife was already captured by Kokseu Sabraq) is in a battle with Kokseu Sabraq, and his horse is shot out from under him, when the four horses of Genghis Khan arrive. The four horses rescue Ong Khan's people, and Ong Khan notes that this is exactly what Temujin's father did for him, and it is happening again, so he will let Sky and Earth decide how he is to repay Temujin.

Ong Khan notices his old age, and wonders about who he's going to leave his people and stuff to. His younger brothers lack strong characters, and his son, well, he might as well be dead. He wonders about making Genghis Khan his heir instead. So Ong Khan and Genghis Khan meet at the Black Forest, where they formally declare themselves father and son. They agree to attack their enemies together, and to disbelieve anyone who tries to talk shit about the other.

To celebrate, Genghis Khan asks Ong Khan's son (Senggum) if he'll let his younger sister marry Genghis's son Jochi, and for Genghis' daughter Kojin Beki to marry Ong Khan's grandson, Tusaka. Senggum gets caught up in a status thing, and says that their family's woman will get to stand by the door of the tent and face the back of the tent, while Temujin's family's woman will have to sit in the back of the tent and face the door. So Senggum didn't want to let go of his younger sister. Temujin is offended, and loses his love for Ong Khan and Senggum.

Jamukha susses all this out, having a been a close friend of Temujin's, and uses it to his advantage. He says his close friend Genghis says one thing about who his father is, but then he's talking to the Naiman, who are enemies of Ong Khan. He says this to Senggum and some of Temujin's younger brothers, and invites them to attack, claiming he'll flank Temujin for them if they do it. They decide to attack Genghis Khan. One of them says that they should attack Temujin's people first, since without his base, he can't really do anything. Senggum send the plan to Ong Khan, and Ong Khan says what the hell, what are you thinking, we're not going to be loved by the Sky if we pull shit like that. Senggum sends the message three times, and Ong Khan rejects it three times, so Senggum goes to meet his father himself, and asks him if he's just going to let Temujin rule their family. Ong Khan asks how he can kill his own son. Senggum storms off, and Ong Khan is scared to lose his relationship with his blood-son, so he calls him back and compromises and basically says 'okay, fine, do what you want'.

Senggum gets together with the other conspirators, and they decide to go through with wedding his younger sister to Temujin's son, but as a lure. Once they have all of Temujin's people for the betrothal feast, they'll attack them.

On getting the invitation, Genghis sets out to join them with ten of his men. On the way there, they spend a night in Monglik's tent. Monglik is suspicious, and points out that Senggum wasn't big on the marriage before, why the change of heart now? He suggests telling Ong Khan's people that because it is spring, the horses are skinny, and they need to fatten them first before they can travel for the feast. So Genghis Khan sends Bukatai and Kiratai to go party in his place, and returns home.

Senggum take Bukatai and Kiratai's arrival to mean they've been found out, and decide to surround and attack Temujin the next morning. One of the conspirator's younger cousins tells his wife about the plan. They're not too keen on it, and their horseherders overhear them. The horseherders spread the rumor from herder to herder, then confirm it. Once confirmed, two of the horseherders decide to warn Temujin about the ambush. They steal off into the night, and get the warning to Genghis Khan. It pays to be well-liked by people of every class.