After the fall of the Liao in 1125, the Khamag Mongols became a leading tribe on the Mongolian Plateau. However, their wars with the Jurchen-ruled Jin dynasty and the Tatar confederation had weakened them. The last head of the tribe was Yesügei, whose son Temüjin eventually united all the Shiwei tribes as the Mongol Empire (''Yekhe Monggol Ulus''). In the thirteenth century, the word Mongol grew into an umbrella term for a large group of Mongolic-speaking tribes united under the rule of Genghis Khan.