He had joined the Gaelic League by 1910 when working in London for the civil service, as had Michael Collins the previous year.

He and Austin Stack had been on their way to meet Sir Roger Casement at Banna Strand in County Kerry in 1916 when they were arrested by the British authorities on Easter Saturday.

They spent Easter Week in Tralee Barracks and in solitary confinement on Spike Island, County Cork; they were then held with Terence MacSwiney, Arthur Griffith and others in Richmond Barracks before being sentenced to penal servitude for life.

[5] In January 1919, Sinn Féin MPs who had been elected in the Westminster elections of 1918 refused to recognise the Parliament of the United Kingdom and instead assembled at the Mansion House in Dublin as a revolutionary parliament called Dáil Éireann.

He was again re-elected for Kerry–Limerick West at the 1922 general election, this time as anti-Treaty Sinn Féin Teachta Dála (TD).