Ōkubo Tadayo (大久保 忠世, 1532 – October 28, 1594) was a samurai general in the service of Tokugawa Ieyasu in the Azuchi–Momoyama period, subsequently becoming a Daimyō of Odawara Domain in early Edo period, Japan.
Ōkubo Tadayo was the eldest son of Ōkubo Tadakazu, a hereditary retainer of the Tokugawa clan. He was born in what is now part of the city of Okazaki in Mikawa Province. Tadayo's nickname was Shinjuro (新十郎). He rose to become considered one of Ieyasu's sixteen generals and was entrusted with Futamata Castle in Tōtōmi Province. Tadayo contributed in the Battle of Azukizaka (1564) against the Ikkō sect in Mikawa province.
At the Battle of Mikatagahara on 1573, Ōkubo Tadayo along with Amano Yasukage led a small band of Tokugawa foot soldiers and matchlock gunners in attacking the Takeda camp,[1] throwing the vanguard of the Takeda army into confusion.
In 1574, Ōga Yashirō, a minor official of Tokugawa clan, colluded with the Takeda clan to overthrow Tokugawa Ieyasu. On the order of the Okazaki magistrate, Ōoka Tadasuke, Tadayo immediately caught Yashirō and paraded him around Hamamatsu Castle, before Tadayo execute Yashirō brutally by mutilating him alive with a saw, while Tadayo crucified the wife and children of Yashirō.[2]
Tadayo accompanied Tokugawa Ieyasu in all of his campaigns, including in the Battle of Nagashino (1575).[3]
Upon the assassination of Oda Nobunaga in 1582, Ieyasu expanded his rule into Shinano Province, with Ōkubo Tadayo assigned to managing the campaign from his base at Komoro Castle.
After the Battle of Odawara (1590), Ieyasu was transferred from the Tōkai region to the provinces of the Kantō region. Toyotomi Hideyoshi ordered that Ōkubo Tadayo be raised at that point to the status of daimyō, and was assigned the fief of Odawara, with an income of 45,000 koku. He continued to rule in Odawara until his death in 1594, and was succeeded by his son, Ōkubo Tadachika.