This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
In 1299, six years after abdicating the Dai Viet throne, Tran Nhan Tong was ordained a Buddhist monk and retreated to Yen Tu Mountain, a documented second career distinct from a retired ruler's quiet withdrawal from public life. There he drew together several earlier strands of Vietnamese Thien, or Zen, teaching into a single unified school, Truc Lam, meaning Bamboo Grove, a documented act of religious founding distinct from simply joining an existing monastic lineage.
He is venerated by the Truc Lam school as its first patriarch, a documented standing distinct from an ordinary monk remembered only within his own generation. Truc Lam's teaching emphasized that religious practice belonged within, rather than apart from, the life of the kingdom, a documented emphasis that its founder's own path, from ruling monarch to unifying Zen teacher, is remembered as embodying directly rather than merely preaching. He died in 1308.
That a king who had just led his kingdom through two Mongol Yuan invasions spent his final years founding a Zen school built on the premise that practice and worldly life are not separate, and is remembered as that school's first patriarch, marks Tran Nhan Tong's religious career as a documented case where a ruler's own path from throne to monastery became his new school's central teaching.