The Khalkhas is also an ancient ethnic group living in the Xinjiang Uighur Autonomous Region, who allied with the Uighurs, the Kazaks and the Mongols and cooperated with the army of the Qing Dynasty to put down the rebellions of the Elder and Younger Khwajas, and maintained the union of China. They live mainly in the Ke'erlesu Khalkhas Autonomous Prefecture in Xinjiang with a population of 140,000.