In the early , the Xi were subordinate to the Khitans. After the Khitans' Li-Sun Rebellion and the Khitans' Ketuyu revolt , the Xi were back to the leading position. The Xi were then back to a golden age, being really active from 755 to 847, providing wide support to An Lushan and the An Shi Rebellion , plundering frequently their neighbours, etc. This aggressive and shiny policy seems to have consumed Xi forces, especially demographic vitality, compare to more calm Khitans. Kumo Xi aggressive policy face to China provoked successives heavy and disastrous battlefield defeat .
When the Uyghur Empire collapsed in the 840's with Tang dynasty already displaying signs of division, the Xi rose in rebellion and were subsequently disastrously defeat by Zhang Zhongwu. The Xi were never able to recover, while the calm Khitans raised to eventually absorb the remnants of Xi people, and established the Liao Dynasty.
It is believed that the ''xiqin'' was derived from a Xi instrument.