Complex sentence: He first joined Conradh na Gaeilge, then the Irish Anti-Partition League, bought (and later sold) the "United Irishman", joined Sinn Féin in London and eventually in 1949 helped to organise a unit of the IRA.
Split into simpler sentences: He first joined Conradh na Gaeilge, then the Irish Anti-Partition League, bought (and later sold) the United Irishman. He joined Sinn Féin in London and eventually in 1949 helped to organise a unit of the IRA.