Éamon de Valera new line. However, a vote to accept the Free State Constitution (contingent on the abolition of the Oath of Allegiance) narrowly failed. Soon afterward, de Valera resigned from Sinn Féin and seriously considered leaving politics. However, one of his colleagues, Seán Lemass, convinced de Valera to found a new republican party. In March 1926, with Lemass, Constance Markievicz and others, de Valera formed a new party, Fianna Fáil ("The Warriors of Destiny"), a party that was to dominate 20th-century Irish politics. While Sinn Féin still held to an abstentionist line, Fianna Fáil was dedicated to republicanising the Free State from
Éamon de Valera Dáil and the electorate, and the anti-Treatyites under the nominal leadership of de Valera, now descended into the Irish Civil War (June 1922 to May 1923), in which the pro-treaty Free State forces defeated the anti-Treaty IRA. Both sides had wanted to avoid civil war, but fighting broke out over the takeover of the Four Courts in Dublin by anti-Treaty members of the IRA. These men were not loyal to de Valera and initially were not even supported by the executive of the anti-Treaty IRA. However, Michael Collins was forced to act against them when Winston Churchill threatened to re-occupy