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 the IRA dumped their arms rather than surrender them or continue a now fruitless war, de Valera returned to political methods. In 1924, he was arrested in Newry for "illegally entering Northern Ireland" and held in solitary confinement for a month in Crumlin Road Gaol, Belfast. During this time, de Valera came to believe that abstentionism was not a workable tactic in the long term. He now believed that a better course would be to try to gain power and turn the Free State from a constitutional monarchy into a republic. He tried to convince Sinn Féin to accept this