The history of Tibet has been made partially known to Europe through the Mongol author, Sanang Setsen,[146] but if free access could be had to their annals, it is probable that a methodical history could be extracted, reaching back at least three centuries before Christ. Tibet was ruled by its own princes till the rise of Genghis; the first monarch, who united the various tribes under his sway B.C. 313, was Seger-Sandilutu-Kagan-Tül-Esen,[147] and from the fact that Buddhism was introduced during his reign, it might be inferred that he came from the south. H’lassa was founded by Srongzan-Gambo, or Srongbdzan sgambouo,[148] about A.D. 630, after which time Tibetan history becomes more authentic, inasmuch as this king introduced the alphabet. The Tang dynasty carried their arms into Tibet from Khoten, but the people threw off their yoke during the decline of that family. Mohammedanism also disturbed the supremacy of the Buddhist faith, and severe persecutions followed about the beginning of the tenth century by an Islam prince Darma, but it was repelled at his death, and has never since made the least impression upon the people. Genghis reduced Tangout, one of the principalities, northeast of Koko-nor, and soon after brought the whole country under his sway; this Kublai still further settled as a dependency of his empire. The people recovered their independence on the expulsion of the Mongols, and under the Ming dynasty formed several small kingdoms, among which were Ladak and Rodok, both of them still existing.