In March 1926 he formed a new party , Fianna FÃ il ( Soldiers of Destiny ) . Soon afterward , de Valera resigned from the presidency of the party and in March 1926 , with SeÃ n Lemass , Constance Markiewicz and others , formed a new party , Fianna FÃ il ( The Warriors of Destiny ) , a party that was to dominate twentieth century Irish politics . While Sinn FÃ in still held to an abstentionist line , Fianna FÃ il was dedicated to republicanising the Free State from within if it gained power .