One of the most traumatic and famous episodes from the younger years of Temujin, later known as Chinggis Khan, was the capture of his wife Borte by the Merkit tribe. The Merkit-Mongol enmity was a longstanding one: Temujin's father Yesugei had stolen Temujin's mother, Hoelun, from the Merkit, and they had harboured their grudge for almost twenty years. When they learned of the young Temujin's survival after the death of Yesugei, and marriage to Lady Borte, they saw their chance to strike. The raid took Temujin unprepared, and he was forced to flee, leaving Borte to be captured by the Merkit.
Temujin fled to mount Burkhan Khaldun to seek insight, then turned to his father's anda and his own overlord, Toghrul of the Kereyit, for justice. Toghrul agreed to attack (likely swayed by promises of loot from the Merkit), and at this point reintroduced Temujin to a friend he had not seen in some years: Jamukha, now a warchief under Toghrul. Together, they set out a few months after the initial raid, and attacked the Merkit. It was not so much a battle as it was a rout: the Merkit fled, and Borte was nearly taken off again until found by Temujin, embracing in a dramatic encounter straight from the cinema:
"As the pillaging and plundering went on, Temujin moved among the people that were hurriedly escaping, calling, 'Borte, Borte!" And so he came upon her, for Lady Borte was among those fleeing people. She heard the voice of Temujin and, recognizing it, she got off the cart and came running towards him. Although it was still night, Lady Borte and Qo'aqcin both recognized Temujin's reins and tether and grabbed them. It was moonlight: he looked at them, recognized Lady Borte, and they fell into each other's arms. After this, that very night Temujin sent a message to Toghrul Khan and to sworn friend Jamukha saying, 'I have found what I was looking for. Let us not travel all night; let us camp here!' He had this message delivered to them. As for the Merkit people who had been fleeing in disarray at night, while still scattering and on the run, they too stopped and spent the night right there.
This is how Lady Borte was rescued from the Merkit tribe, and how she was reunited with Temujin."
-adapted from The Secret history of the Mongols, de Rachewiltz translation, section 110, page 38.
You can learn more on this episode, and the consequences of it, in my latest video: https://youtu.be/mYe5uYXb5PI