In August 1180, when Minamoto no Yoritomo raised his banner in Izu, Okazaki Yoshizane was among the first to rally alongside the Miura clan. At the Battle of Ishibashiyama, Yoritomo's forces suffered a crushing defeat against the large Taira-aligned army led by Oba Kagechika. In that battle, Yoshizane's son Sanada Yoshitada engaged enemy commander Matano Kagehisa in single combat and was killed. Despite losing his son, Yoshizane fled with Yoritomo to Awa Province and continued to serve in building the shogunate. The desperate loyalty of early retainers like Yoshizane—who gave their sons' lives—formed the very foundation upon which Yoritomo established Kamakura as his base. Yoshitada is enshrined to this day at the Sanada Reisha in Odawara as a deity of martial valor.