He was born the eldest son of Tokugawa Tsunashige, lord of Kōfu and a grandson of the third shogun Tokugawa Iemitsu. But because he was born just before his father took his official wife, his birth was kept secret, and he was raised in the house of the retainer Shinmi Masanobu under the name Shinmi Sakon. He was later called back as his father's heir and took the name Tsunatoyo.
When his father Tsunashige died, he succeeded him as lord of the Kōfu domain. He grew up under the care of his grandmother Junshōin. He deeply trusted his foster father Shinmi Masanobu and is said to have kept defending him even when retainers jealous of Shinmi made false accusations. His compassionate character would later show in his government.
When the fourth shogun Tokugawa Ietsuna fell gravely ill without a son, Tsunatoyo became a leading candidate for the next shogun together with his uncle Tokugawa Tsunayoshi. But the rōjū Hotta Masatoshi strongly backed Tsunayoshi, more closely related to Iemitsu, and the post went to Tsunayoshi. Tsunatoyo remained lord of Kōfu.
On the recommendation of the scholar Kinoshita Jun'an, he invited Arai Hakuseki to be his tutor. Tsunatoyo is said to have eagerly studied Confucianism with Hakuseki, as well as the deeds of the shoguns from Tokugawa Ieyasu to Iemitsu. He trusted the strict Hakuseki, whom some called a "demon", to the very end, and their bond was described as "one body in two persons".
He had Hakuseki compile, in just ten months, the genealogies and brief histories of the daimyo families over some eighty years from around the Battle of Sekigahara. This was the Hankanfu, which Tsunatoyo is said to have always kept at hand. Knowing the histories of the daimyo later greatly helped him in governing the realm.
Since Tsunayoshi also had no son to succeed him, Tsunatoyo's status as Iemitsu's grandson was valued, and he was formally chosen as the shogun's heir. He became Tsunayoshi's adopted son, changed his name to Ienobu and moved into the western enclosure of Edo Castle. It is said that he refused every celebratory gift, close to bribes, that daimyo brought him.
When Tsunayoshi died, he became the sixth shogun. Tsunayoshi had left word that the laws of compassion be kept, but Ienobu is said to have abolished most of them in turn "for the sake of all the people". He employed Manabe Akifusa as sobayonin and Arai Hakuseki as scholar, promoting a government that valued learning and propriety.
Adopting Hakuseki's advice, he moved to create the Kan'in-no-miya as a new princely house so that the imperial line would not die out. He also revised the Buke Shohatto, the laws for warrior houses, setting out the warrior's duties more clearly. The government of his reign and that of the next shogun Ietsugu are together called the Shōtoku reforms.
A Korean embassy came to celebrate the new shogun. On Hakuseki's advice, the reception was simplified to cut costs, and the shogun's title in diplomatic letters was changed. Hakuseki came under heavy pressure over these measures, but Ienobu is said to have supported him. It was an attempt to shape diplomacy on an equal footing.
He caught an epidemic illness, believed to have been influenza, and died just over three years after becoming shogun. On his deathbed he heeded Hakuseki's advice and chose his young fourth son Ietsugu as heir. When an attendant who had long served him began to weep, he gently chided him, saying, "Is it not natural for people to die?" He is recorded as a compassionate shogun.
Tokugawa IeyasuTokugawa IemitsuTokugawa IetsunaTokugawa TsunayoshiArai HakusekiOgiwara Shigehide
Yanagisawa YoshiyasuOgiwara ShigehideŌishi Kuranosuke (Yoshio)Ichikawa Danjūrō IOgyū SoraiAmenomori HoshuŌoka TadasukeTokugawa Yoshimune
People of the Edo period ・ People by period
Based on facts found in textbooks and biographies. Uncertain points are marked as such.