evidence: In any age, even in our nuclear age, such a landmass constitutes a formidable buffer or barrier for any power operating beyond Tibet. Though Tibet itself posed no existential threat to China, there were periods in history when the Tibetans burst out of the plateau and wrested the prosperous oasis towns of Khotan, Kucha, Karashar and Kashgar in Turkestan from Tang China around 666.5 "The Tibetan Empire ruled the Southern Route of the Silk Road and most of Gansu Corridor, including Khotan, Lob-nor, and Dunhuang, for over fifty years from the late 8th to the mid 9th centuries." 6 In 763 Tibetan troops captured the Chinese imperial capital Ch’ang-an (Xian of present-day China) and put a new emperor on the throne. 7 [...] With the breach of the buffer, an enfeebled Manchu China was convinced that the British might mount an invasion of China through Tibet. The only way to prevent this from happening was to take control of Tibet. As one Manchu official put it, "Tibet is the buttress on our national frontiers – the hand, as it were, which protects the face."11