Founds INLA and IRSP
At a meeting in the Lucan Spa Hotel near Dublin, on 10 December 1974, the Irish Republican Socialist Party was formed by republicans, socialists, and trade unionists with Costello as the Chairperson.
At a private meeting later the same day, the Irish National Liberation Army was formed with Costello as the Chief of Staff, although its existence was to be kept secret for a time. The new grouping intended to combine left politics with the "armed struggle" against British security forces in Northern Ireland.
Within days of its founding, the fledgling Irish Republican Socialist Movement was embroiled in a bitter feud with the Official IRA. The feud resulted in the attempted assassination of Official IRA leader Sean Garland who was wounded in an IRSP attack near his home in the Ballymun area of Dublin (Garland was wounded six times but survived the attack). Before a truce was reached, three members of the IRSP were dead. Later that same year, Bernadette McAliskey resigned from the IRSP over the failure of a motion that would have brought the INLA under IRSP control, taking over half of the Árd Chomhairle members with her.
In July 1976 Costello was replaced as INLA chief-of-staff by South Derry man Eddy McNicholl, although he still wielded considerable influence within the movement, retaining his position as chairman of the IRSP.
Read more about this topic: Seamus Costello