Since Iruka considered Prince Yamashiro no oe (it is said that he was a son of Prince Shotoku) a powerful candidate for succession to the Imperial Throne, as an obstacle, he launched an attack on Ikaruganomiya Palace and dethroned Prince Yamashiro no oe and his family in November, 643.
そのため、有力な皇位継承資格者・山背大兄王（通説では聖徳太子の子）の存在が邪魔になり、643年11月、入鹿は斑鳩宮を襲い山背大兄王とその一族を滅ぼした。