Irish Republic the Third Dáil, and all future institutions arising from it, as illegal. (See Second Dáil). The anti-Treaty side was then defeated in the Civil War. Most militant opposition to the Free State came to an end on 24 May 1923 when Frank Aiken, chief-of-staff of the IRA issued the order to "dump arms" and Éamon de Valera issued his address to the "Legion of the Rearguard". Éamon de Valera continued as president of the Sinn Féin political party. In March 1926, Éamon de Valera, along with most anti-Treaty politicians, founded a new party called 'Fianna Fáil' and ended their boycott
Éamon de Valera elected a Fellow of the Royal Society (FRS), a recognition of his lifelong interest in mathematics. He also served as a member of the Parliament of Northern Ireland (for Down from 1921 to 1929 and for South Down from 1933 to 1937), although he held to the republican policy of abstentionism and did not take his seat in Stormont. De Valera was criticised for ending up as co-owner of one of Ireland's most influential group of newspapers, Irish Press Newspapers, funded by numerous small investors who received no dividend for decades. De Valera is alleged by critics to have helped