The initial introduction of Lamaist Buddhism did not stick, however, and the old Bon religion re-emerged in the ninth century. Under persecution, Buddhism, centered in Amdo, was transformed and the rNying-ma-pa school arose. Rival schools challenged it, and religious and political wars beset the area until the Mongols conquered it. They imposed Lamism and allowed the state supression of dissident schools like the rNying-ma-pa.
In the 20th century, communism attempted the suppression of all religions, including Lamism, but had little success.