In 1333, he was asked to join the armed uprising by Takauji ASHIKAGA to overthrow the Shogunate, and Sadahisa attacked the Chinzei tandai Hidetoki HOJI along with Sadatsune SHONI and Sadamune OTOMO, forcing HOJO to commit suicide.
1333年（元弘3年）足利尊氏の倒幕挙兵勧誘により、少弐貞経、大友貞宗と共に鎮西探題北条英時を攻撃、自刃に追い込む。