The nine mountain schools (九山; or gusan) were the initial monasteries of the Korean branch of Buddhism called Seon, founded in the Unified Silla period in the 8th or 9th century. The initial transmission of Seon into Korea is usually attributed to Beomnang (法朗; fl. 632-646), said to be a student of the Chinese master Daoxin (道信; 580-651). Seon was later popularized especially by Sinhaeng (神行; 704-779) in the latter part of the eighth century and by Doui (道義; d. 825) at the beginning of the ninth century. From then on, many Koreans studied Chan in China and, upon their return, established their own schools at various mountain monasteries with their leading disciples.