It says Tibet has been a part of China since the 13th century, when the Mongol empire, which conquered China and formed the Yuan dynasty, also conquered Tibet. Western and central parts of Tibet are administered by China as the Tibet Autonomous Region, while eastern parts of the region fall under China's Sichuan, Qinghai, Yunnan and Gansu provinces.
After several decades of de facto independence beginning in 1912, Tibet was over-run by China's People's Liberation Army in 1950 to enforce the newly-formed People's Republic of China's claim of sovereignty over Tibet.
In 1959, thousands of Tibetans surrounded the Dalai Lama's palace in Lhasa --- the Tibetan capital -- to protect him against what was rumored to be a plot by the Chinese military to abduct him. The gathering turned into an all-out revolt against Chinese rule, which was suppressed by the PLA. The Dalai Lama fled to India, where he has remained in exile ever since.