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.
Rúaidhrí de Valera 1947, de Valera became the Archaeological Officer for Ordnance Survey Ireland which permitted him to develop the Survey of the Megalithic Tombs of Ireland project. He went on to write significant papers on Irish prehistory which contributed to his doctorate, awarded in 1954. In 1957, de Valera was appointed Chair of Celtic Archaeology at University College Dublin where he worked to enlarge the department whilst continuing to publish on Irish chamber tombs, especially the Court cairns which he proposed first developed in the west of the country. De Valera later excavated at the Mound of the Hostages at Tara. He