The Yarlung dynasty originated in the Yarlung Valley and evolved into the Tibetan Empire in the 7th century under the rule of Songtsen Gampo (618-650 CE). Songtsen Gampo unified the Tibetan plateau, established Lhasa as the capital, introduced Buddhism, and developed the Tibetan script. His marriages to Nepalese Princess Bhrikuti and Chinese Princess Wencheng fostered important diplomatic ties.