In the 1050s, the Khitans of the Liao Dynasty attacked the Jalair, a Darligin Mongol tribe living along the Kerulen River in the far-eastern region of Mongolia.
The Jalair fled to the Borjigin Mongols led by Queen Monolun (Nomulun in the Secret History), the mother of Khaidu.
So they mockingly waved their hats and sleeves from the other side of the river shouting "Come and plunder our livestock!"
Because the Khitan army was numerous they skilfully gathered dry branches and dead wood and in one night built a dam to cross of the river.
Because the Jalairs were experiencing dreadful hunger they dug out the roots of a plant called sudusun which was regarded as edible in that area and ate it.
They ended up leaving the horse pastures of Monolun's sons all dug up and full of holes.
When Nachin learnt about the treacheries committed by the Jalairs and the death of his brother Dutum Menen's sons he hid Khaidu in a large vessel in which Mongols drained kumiss (fermented mare's milk) and kept him there.