Sinn Féin for nine years. (It merged with two other organisations to form Fine Gael in 1933.) Anti-Treaty Sinn Féin members continued to boycott the Dáil. At a special "Ard Fheis" in March 1926, de Valera proposed that elected members be allowed to take their seats in the Dáil if and when the controversial Oath of Allegiance was removed. When his motion was defeated, de Valera resigned from Sinn Féin; on 16 May 1926, he founded his own party, Fianna Fáil, which was dedicated to republicanising the Free State from within its political structures. He took most Sinn Féin TDs with him.
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