From the 7th to the 11th century a series of emperors ruled Tibet – see List of emperors of Tibet - of whom the three most important in later religious tradition were Songtsen Gampo, Trisong Detsen and Ralpacan, "the three religious kings" (mes-dbon gsum), who were assimilated to the three protectors (rigs-gsum mgon-po), respectively Avalokiteśvara, Mañjuśrī and Vajrapāni. Songtsen Gampo (c. 604 – 650) was the first great emperor who expanded Tibet's power beyond Lhasa and the Yarlung Valley, and is traditionally credited with introducing Buddhism to Tibet.