Minamoto no Yoshiie (1039–1106), known by the warrior name 'Hachimantaro Yoshiie' from his coming-of-age ceremony at Iwashimizu Hachimangu, is said to have founded this Hachimangu at Shiraoka during his march northeast in the Former Nine Years' War (1051–1062), enshrining the Hachiman deity here and praying for victory. Together with his father Yoriyoshi, Yoshiie went on to subdue the northern warriors Abe Yoritoki and Sadato, pacifying the Tohoku region. His martial reputation left a deep impression on the warriors of the Kanto plains, cementing his status as the undisputed head of the Minamoto clan. Shiraoka Hachimangu, where Yoshiie prayed at the outset of his eastern campaign, continued to be revered by Kamakura warriors and remains a historic site today.