With respect to these outer regions, the Qing maintained imperial control, with the emperor acting as Mongol khan, patron of Tibetan Buddhism and protector of Muslims. However, Qing policy changed with the establishment of Xinjiang province in 1884. During The Great Game era, taking advantage of the Dungan revolt in northwest China, Yaqub Beg invaded Xinjiang from Central Asia with support from the British Empire, and made himself the ruler of the kingdom of Kashgaria. The Qing court sent forces to defeat Yaqub Beg and Xinjiang was reconquered, and then the political system of China proper was formally applied onto Xinjiang. The Kumul Khanate, which was incorporated into the Qing empire as a vassal after helping Qing defeat the Zunghars in 1757, maintained its status after Xinjiang turned into a province through the end of the dynasty in the Xinhai Revolution up until 1930. In the early 20th century, Britain sent an expedition force to Tibet and forced Tibetans to sign a treaty. The Qing court responded by asserting Chinese sovereignty over Tibet, resulting in the 1906 Anglo-Chinese Convention signed between Britain and China. The British agreed not to annex Tibetan territory or to interfere in the administration of Tibet, while China engaged not to permit any other foreign state to interfere with the territory or internal administration of Tibet. Furthermore, similar to Xinjiang which was converted into a province earlier, the Qing government also turned Manchuria into three provinces in the early 20th century, officially known as the "Three Northeast Provinces", and established the post of Viceroy of the Three Northeast Provinces to oversee these provinces, making the total number of regional viceroys to nine.