The Rise of Tibet and Princess Wencheng
Also called: Tibetan Empire
Songtsen Gampo, who had united the Tibetan plateau, married the Tang Princess Wencheng in 641. He ruled from Lhasa and brought Buddhism and a Tibetan script to his realm.

Yan Liben · Public domain · Source
In the early 7th century Songtsen Gampo united the clans of the Tibetan plateau into the Tibetan Empire and made Lhasa his capital. After fighting the Tang and demanding a marriage alliance, he received Princess Wencheng, a kinswoman of Taizong, in 641, and is said to have taken a Nepali princess as well. Buddhism came in with the two queens and the Jokhang temple was founded, and a Tibetan script based on an Indian one is said to have been created.
Tibet went on to threaten the Tang west; in 763, after the An Lushan Rebellion, it even occupied Chang’an briefly. Sources differ on Songtsen Gampo’s dates of birth and death.