After his father's death, he split off with a faction of Naimans to rule just south of the Altai Mountains, near the source of the Ulungur river, while his brother Tayang Khan remained in the heart of the Naiman homeland between the Black Irtysh and Bukhtarma rivers.
[1] According to a story, he, along with the Oirat chief Quduqa Bäki, used a jada or "thunder stone" to unleash a powerful storm on Genghis' army.
Buyruq, troubled by this storm, left the alliance and retreated to the south side of the Altai Mountains.
[2] He was soon attacked by Keraites led by Toghrul in 1202, in alliance with Genghis on shores of Soqoq-Usun river (in modern Ulaangom).
[3] Caught unprepared, Buyruq fled and crossed Altai, arriving at Ulungur river.