The Akamatsu clan had fallen by the attack from the army of bakufu (Japanese feudal government headed by a shogun) since Mitsusuke AKAMATSU murdered the 6th shogun of Muromachi bakufu Yoshinori ASHIKAGA, which called Kakitsu War in 1441.
赤松氏は嘉吉元年（1441年）に赤松満祐が室町幕府第6代将軍・足利義教を殺害するという嘉吉の乱で幕府軍に攻められて滅亡していた。