Battle of Mikatagahara
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, and accompanied Tokugawa Ieyasu in all of his campaigns, including the Battle of Mikatagahara (1573).