Tadayo was the son of Okubo Tadakazu and served Tokugawa Ieyasu as a general and an advisor. He played a notable role in the Battle of Mikatagahara, leading a night raid with Amano Yasukaga against the Takeda positions. Later, he occupied an exposed position at Nagshino and took heavy losses fighting with Takeda men under Yamagata Masakage. He was one of the commanders in Ieyasu's failed endeavor to chastise Sanada Masayuki in 1585 and that same year was tasked with holding Okazaki castle (Mikawa province) following the defection of Ishikawa Kazumasa to the Toyotomi. In 1590 he was given Odawara castle in Sagami with an income of 45,000 koku.
- Initial text from Samurai-Archives.com FWSeal & CEWest, 2005