He was born in Mikawa Province, the second son of Honda Toshimasa. The Honda had served the Matsudaira for generations, and Masanobu served Matsudaira Motoyasu, the future Tokugawa Ieyasu, from youth. Five years older than Ieyasu, he grew up watching his lord's hard early years as a fellow Mikawa warrior.
When Imagawa Yoshimoto invaded Owari, Masanobu followed Ieyasu, then on the Imagawa side, in the attack on the Marune fort. He is said to have been wounded in the knee and to have limped ever after. With Yoshimoto slain, Ieyasu broke from the Imagawa and became independent in Mikawa.
When followers of the Ikko sect in Mikawa rose against Ieyasu, Masanobu, a devout believer, joined the rebels with his brother Masashige and fought his lord. Torn between faith and loyalty, he chose his faith. The next year Ieyasu put down the uprising.
After the uprising was crushed he left Mikawa and is said to have gone via Kyoto to Kaga, where he may have fought Oda Nobunaga on the side of the Ikko rebels. Another story says he served Matsunaga Hisahide of Yamato, who is said to have praised his ability, but this is uncertain.
Through the mediation of Okubo Tadayo he was allowed to return to Ieyasu. Accounts of when he returned differ, but by this time at the latest he had regained Ieyasu's trust. After the Honnoji Incident, when Ieyasu took Kai and Shinano, Masanobu governed them as a magistrate.
When Ieyasu submitted to Toyotomi Hideyoshi, Ieyasu's chief retainers received court ranks on Hideyoshi's recommendation, and Masanobu was made Governor of Sado with the junior fifth rank, lower grade. It showed that the man who had once raised arms against his lord was now publicly recognized as a senior retainer.
After the Odawara campaign, when Ieyasu moved to the Kanto, Masanobu received a fief of 10,000 koku at Tamanawa in Sagami and became a daimyo. He also helped build up the new base, for example supervising construction in Edo while Ieyasu was away.
In the Sekigahara campaign he joined the army of Ieyasu's son Hidetada. He is said to have advised Hidetada to stop attacking Ueda Castle in Shinano, without success. Some research, however, holds that he actually returned to Edo partway and took charge of defending the Kanto.
At Honganji the brothers Kyonyo and Junnyo were at odds. Masanobu is said to have urged Ieyasu to use this to divide the temple, and this year Ieyasu gave Kyonyo land in Kyoto, creating Higashi Honganji. It was also a way to weaken the Honganji to which Masanobu had once devoted himself.
When Ieyasu became shogun and opened the Edo shogunate, Masanobu, as a close aide, came to run its government in practice. Ieyasu is said to have trusted him so much that he called him his friend, and the two talked long in private. He served through wisdom and strategy rather than feats of arms.
After Ieyasu passed the shogunate to Hidetada and moved to Sunpu, Masanobu took part in government under Hidetada in Edo, and from this year was Hidetada's toshiyori, later called roju. His son Masazumi served at Ieyasu's side in Sunpu, so father and son linked the two centers of power.
When Ieyasu died that spring, Masanobu passed the headship to Masazumi, withdrew from government and died about two months later, ending a life spent beside Ieyasu. He is said not to have sought large fiefs and to have warned his son not to accept too much.
Matsunaga HisahideImagawa YoshimotoOda NobunagaToyotomi HideyoshiTokugawa Ieyasu
Hōjō UjimasaAshikaga YoshihideImagawa UjizaneNabeshima NaoshigeChōsokabe MotochikaHasegawa TōhakuToyotomi HidenagaKuki Yoshitaka
People of the Sengoku/Azuchi-Momoyama period ・ People by period
Based on facts found in textbooks and biographies. Uncertain points are marked as such.