Prior to de Valera's political career, he was a commandant at Boland's Mill during the 1916 Easter Rising. He was arrested, sentenced to death but released for a variety of reasons, including the public response to the British execution of Rising leaders. He returned to Ireland after being jailed in England and became one of the leading political figures of the War of Independence. After the signing of the Anglo-Irish Treaty, de Valera served as the political leader of Anti-Treaty Sinn Féin until 1926, when he, along with many supporters, left the party to set up Fianna Fáil, a new political party which abandoned the policy of abstentionism from Dáil Éireann.