Ruairi O Bradaigh, who has died at the age of 80, never deviated during his long republican career from his profound belief that the British presence was the sole cause of all Ireland's woes. He also never departed, from first to last, from his stance that the institutions that rule Ireland are not legitimate and that republicans are entirely justified in using force to bring them down.
He put his beliefs into violent practice, most notably as an IRA leader in its most violent period, the early 1970s, and later as political head of one of the dissident republican groups which continue their violence today. His opinions meant he was always isolated from mainstream Irish nationalism. In recent decades he became cut off from mainstream republicanism too, utterly opposed as he was to the strategy of Gerry Adams and others of taking republicanism into politics.
But such isolation never cost him a moment's concern. He was known as one of the old IRA's sea-green incorruptibles, completely uninterested in money and position and completely uninterested, too, in anything short of Britain's surrender and withdrawal. He was once described by the FBI as "a national security threat, a dedicated revolutionary undeterred by threat or personal risk." Private Eye regularly sneered at him, meanwhile, as "Rory O'Bloodbath".
He was born in 1932 in the Irish Republic. His mother and father, both active republicans, named him Peter Roger Casement Brady in memory of Roger Casement, a republican martyr executed by the British for his part in the 1916 Rising. He later Gaelicised his name.
Probably the most academic of the IRA leaders of the time, he came from a middle-class cosmopolitan background. A devout Catholic who abstained from alcohol, he moved in his teens to Dublin where he took a degree in commerce. Joining Sinn Fein and the IRA at an early age, he was involved in the small-scale and ill-supported campaign launched by the IRA in 1956.
He came to prominence by taking part in a raid on an army barracks in Berkshire which yielded guns and ammunition. Although most of this was recovered before it could be smuggled to Ireland, the incident made O Bradaigh's reputation, and he briefly became IRA chief of staff before the campaign petered out for lack of public support. Arrested many times and imprisoned on a number of occasions, he is said to have been author of the statement which announced the ending of the campaign.
When the Troubles erupted in the north in 1969 the republican movement split, with O Bradaigh and other veterans taking charge of the larger and more militant faction, the Provisional IRA. Though no longer an active gunman or bomber, he was one of the principal directors of the IRA as it expanded into the most lethal of the various combatants. In 1972, for example, it was responsible for 229 of the year's 500 deaths.
By the mid-1970s, however, many militant northern republicans tired of his leadership, and in particular his part in approving a ceasefire which was said to be disastrous for the IRA.
Young turks, headed by Gerry Adams and Martin McGuinness, seized control in a bloodless coup, claiming that during the ceasefire the British "probably came as near at that time to defeating the republican struggle than at any other time."
O Bradaigh had been duped, they argued, into believing that Britain was seriously considering withdrawal from Northern Ireland. He stayed on as president of Sinn Fein but as a figurehead, his power gone. Things came to a head at a packed meeting in Dublin in 1986 when the Adams-McGuinness faction sought to ditch decades of republican tradition to allow Sinn Fein candidates to take seats in the Dublin parliament.
Everyone knew that O Bradaigh had always held that ending traditional abstentionism would spell the beginning of the end for armed struggle and lead on to what he denounced as constitutionalism. He insisted: "The armed struggle and sitting in parliaments are mutually exclusive. Parliament is a substitute for a national liberation struggle. It is there to contain and draw off revolutionary fervour."
As he spoke in the debate he was perspiring and over-emotional, his words tumbling out not always in sentences. One commentator wrote: "In contrast to the young, confident, self-assured men who made up the new leadership, he looked old-fashioned, desperate: a loser. They seemed to look forward while he looked back."
The key speech against him came from McGuinness. who promised delegates: "Our position is clear and it will never, never, never change: the war against British rule must continue until freedom is achieved."
When the vote went against him O Bradaigh and a small group of supporters shouldered their way out of the meeting, later announcing the formation of a new group which they called Republican Sinn Fein.
In later life he took a grim satisfaction in declaring that he had been correct in predicting that the new leadership would eventually opt for politics and preside over the disbandment and disarmament of the IRA. A few years ago when McGuinness denounced dissidents such as him as "traitors," O Bradaigh retorted that he was guilty of treachery.
Ever since then Republican Sinn Fein has been an insignificant group, in two decades failing to attract any appreciable support. But it spawned a military wing, the Continuity IRA, which over the years has claimed a number of lives. "As long as the British remain, there will always be some kind of IRA," O Bradaigh shrugged. Suffering from ill-health, he retired as head of Republican Sinn Fein in 2009.
An implacable warrior who regarded himself as keeper of the sacred republican flame, he vowed that he would never accept Ireland's present "illegitimate" institutions. And he never did.
He is survived by his wife Patsy and their six children.
Ruairi O Bradaigh, republican leader: born Longford, Irish Republic 2 October 1932; married (six children) died 5 June 2013.