Saicho was a Buddhist monk during the Heian Period, and he founded the Tendai School of Buddhism in Japan. He was born in Furuichi Village, Shiga County, Omi Province (present day Otsu City, Shiga Prefecture), and his popular name was MITSU no Obito Hirono. There is another theory that states that he was born in 766.
His ancestor was King Tomaki, a descendant of Emperor Koken in the Later Han Dynasty, who came from abroad to Japan during the period of Emperor Ojin.
His age is based on the view that he was born on the first year of Jingokeiun.
On November 12, 780, at the age of 14, he was ordained as a substitute for the provincial monastery priest and he changed his name to Saicho.
On January 20, 783, at the age of 17, he received the official certification, which validated him as an officially recognized priest.
In 785, at the age of 19, he received gusoku-kai (a higher form of ordination) at Todai-ji Temple. In July of the same year, he entered into the ascetic training in the mountains at Mt. Hiei-zan, and he completed the reading of Daizo-kyo Sutra.
In 797, he became one of the Ten Zen Priests of Naigubu.
In 802, he became the lecturer of Hokke-e meeting at Takaosan-dera Temple (Jingo-ji Temple). He was selected as one of the scholars sent to China for a short-term stay in order to study the dharma in China.
In July, 804, accompanied by his disciple, Gishin, as a translator he left Kyushu, along with Kukai. In September, he arrived in present day Ningbo. He went to Mt. T'ient'ai and studied the T'ient'ai doctrine from Miao-lo's disciples, Dozui (Tao-sui) and Gyoman (Hsing-man). Furthermore, he received the bodhisattva precepts from Dozui, the zen teachings from Shukunen (Hsiao-jan) and the anointment of Esoteric Buddhism from Jungyo (Shun-hsiao).
On his way back, he landed at Cape Wada (Kobe City) in May, 805, and founded Nofuku-ji Temple, which was the first site where the edification of Esoteric Buddhism took place. He came to Kyoto in July, and the number of Buddhist scriptures he transcribed while he was abroad amounted to 230 volumes and 460 chapters. When he returned to Japan, Emperor Kammu was ill, and he prayed for the Emperor's recovery from illness in the Court.
In January, 806, upon Saicho's request, Tendai Buddhism was permitted to have 2 for Tendai-gyo training (ordained priests to be trained; 1 for Shikan-gyo and 1 for Shana-gyo) every year. This conforms to the Six Schools of the South Capital (Nara). This was the beginning of Tendai Buddhism in Japan.
During the same time period, he borrowed scriptures from Kukai and studied Shingon Buddhism, Sanskrit and Garland Sutra.
In November, 813, he made a request to Kukai to borrow 'Rishushakkyo,' but Kukai refused by indicating that 'it can be obtained not by studying the words but by practicing and training,' and after that, there were no more communications between them because of differences in their opinions.
In 815, upon request by Wake clan he lectured at Daian-ji Temple, and he had a debate with Buddhist scholars from Nara. After that, he left for the Eastern Provinces. He based himself at Mitono-ji Temple associated with Ganjin (Chien-chen) in Kozuke and Ono-dera Temple in Shimotsuke, and he began his missionary activities in the Kanto area.
He had a debate on San-ichi Gonjitsu (One-provisional and three-true teaching vehicles) with Tokuitsu AIZU, a Buddhist scholar of Hosso School (the Dharma Characteristics School). Tokuitsu made an argument against Saicho by authoring "Busshosho," and Saicho made a counterargument in "Shogon-jikkyo." The debate continued even after he returned to Mt. Hiei-zan and he authored "Hokkekowaku," "Shugo-kokkai-sho" (An Essay on the Protection of the Nation), "Ketsu-gonjitsu-ron" and "Hokke Shuku" (The Outstanding Principles of the Lotus Sutra), but since both Saicho and Tokuitsu died before the debate ended, Saicho's disciples ended the debate by announcing that Tokuitsu's assertions were entirely outdebated.
He voluntarily annulled the gusoku-kai. He established "Sange-gakushoshiki" (The Regulations for Students of the Mountain School), and he required that those who underwent Tendai School training to take Mahayana precepts to become bodhisattva priests and to train themselves in the mountains for 12 years.
In response to the counterargument from the Sogo (Priest Office) of Nara, he wrote "Kenkai Ron" (A Clarification of the Precepts). He wrote "Naisho-Buppo-Kechimyakufu" and preached his legitimacy.
He passed away at the age of 56 at Chudo-in Hall at Mt. Hiei-zan on June 26, 822. Mediated by his disciple, Kojo, FUJIWARA no Fuyutsugu and YOSHIMINE no Yasuyo, the construction of Daijo-Kaidan (Mahayana ordination center) was chartered 7 days after his death.
In 866, he was given an honorific posthumous name of Dengyo Daishi.
As a Calligrapher
It is not clear under which master he was trained in calligraphy, but he went to China in 804, and upon returning to Kyoto he brought back with him the Seventeen Books of O Gishi (Wang Xizhi) as well as calligraphy textbooks and works of calligraphy by O Kenshi (Wang Xianzhi), O Yo-Jun and Cho Suiryo (Chu Suiliang). His style of calligraphy is clear and elegant compared to Kukai's, which is protean. The genuine works by him that still exist today include the following.
Kyukaku Jo (Book)
This is a sekitoku (a letter written in Chinese) dated November 25, 813, and addressed to his disciple, Taihan, whom Saicho had sent to study Shingon Buddhism under Kukai.
It is named so because it begins with 'Kyukaku Sei'on.'
At Nara National Museum. A National Treasure.
Shorai Catalogue (Esshuroku)
This is a catalogue of instruments used in Buddhism, kyoso (notes on sutras) and written works related to Tendai Buddhism that he either collected or transcribed in Yuezhou (Zhejiang) while he was in China in 805. This is a printed style of writing Chinese characters which has flowing brush strokes of O Gishi style, just as in Kyukaku Jo. At Enryaku-ji Temple. A National Treasure.
This is a fragment from a catalogue of items that were requested to be brought back from China, which were presented to Mt. Hiei-zan by Saicho in 811, and named so because of the characters found on the first line. Every paper has Mt. Hiei-zan's stamp. At Enryaku-ji Temple. A National Treasure.