Chih-i had advanced the correct interpretation of the Lotus Sūtra’s One-vehicle teaching, but the T’ien-t’ai School had been eclipsed by the popularity of the Fa-hsiang School and its Three-vehicle teachings. However, even at the height of the Fa-hsiang School’s popularity and influence, Chinese monks who were versed in Yogācāra doctrine, such as Fa-pao and Lingjun, had argued for a One-vehicle interpretation of Buddhism. Eventually, the One-vehicle teachings of Fa-tsang’s Hua-yen School and the One-vehicle Esoteric teachings of Subhakarasirpha and Vajrabodhi received the support of the state, and the Three-vehicle teachings were vanquished. As Saichō declared in the Shugo kokkaishō: “The years during which the expedient (Three-vehicle teachings flourished) have already set with the western sun. The sun of the ultimate (teaching of the One-vehicle) will rise in the east (Japan).’

Saichō dated the rise of the One-vehicle teaching in Japan with the allocation of yearly ordinands to the Tendai School in 806. The date suggests that Saichō believed that he was the messenger who had brought the new teaching to Japan and that he was responsible for defending it.