Kingdom of Dali
The position of the People's Republic of China (PRC), which has ruled mainland China since 1949, as well as the official position of the Republic of China (ROC), which ruled mainland China before 1949 and currently controls Taiwan, is that Tibet has been an indivisible part of China "de jure" since the Yuan dynasty of Mongol-ruled China in the 13th century, comparable to other states such as the Kingdom of Dali and the Tangut Empire that were also incorporated into China at the time.