Tibetan Empire
The Tibetan Empire (, Great Tibet; ) was an empire centered on the Tibetan Plateau, formed as a result of imperial expansion under the Yarlung dynasty heralded by its 33rd king, Songtsen Gampo, in the 7th century. The empire further expanded under the 38th king, Trisong Detsen, and expanded to its greatest extent under the 41st king, Rapalchen, whose 821–823 treaty was concluded between the Tibetan Empire and the Tang dynasty. This treaty, carved into the Jokhang Pillar, delineated Tibet as being in possession of an area larger than the Tibetan Plateau, stretching east to Chang'an, west beyond modern Afghanistan, and south into modern India and the Bay of Bengal. The Yarlung dynasty was founded in 127 BCE in the Yarlung Valley along the Yarlung River, south of Lhasa. The Yarlung capital was moved in the 7th century from the palace Yumbulingka to Lhasa by the 33rd king Songsten Gampo, and into the Red Fort during the imperial period which continued to the 9th century. The beginning of the imperial period is marked in the reign of the 33rd king of the Yarlung dynasty, Songtsen Gampo. The power of Tibet's military empire gradually increased over a diverse terrain. During the reign of Trisong Detsen, the empire became more powerful and increased in size. At this time, a 783 treaty between the Tibetan Empire and the Tang dynasty defined the borders, as commemorated by the Shol Potala Pillar in Lhasa. Borders were again confirmed during the later reign of the 41st king Ralpachen through his 821–823 treaty between the Tibetan Empire and Tang dynasty, which was also commemorated by three inscribed stelae. In the opening years of the 9th century, the Tibetan Empire controlled territories extending from the Tarim Basin to the Himalayas and Bengal, and from the Pamirs into what are now the Chinese provinces of Sichuan, Gansu and Yunnan. The murder of King Rapalchen in 838 by his brother Langdarma, and Langdarma's subsequent enthronement followed by his assassination in 842 marks the simultaneous beginning of the dissolution of the empire period.