The veteran Irish republican, Joe Cahill, has died following a short illness.
Cahill was considered the father figure of modern republicanism
The 84-year-old died in Belfast on Friday.
He was named by the British army in the early 1970s as the IRA's chief of staff, at a time when the organisation was waging a campaign of bombings and shootings in Northern Ireland and England.
Cahill was sentenced to death for the murder of a policeman, but had his sentence commuted to life in 1942 after the intervention of the then Pope.
Born in Belfast in 1920, Joe Cahill dedicated much of his life fighting partition.
In 1969, he was a key figure in founding the Provisional IRA and was Belfast commander before becoming chief of staff.
He was released from prison in the 1950s but in 1973, he was again jailed for gun-running after being convicted of importing weapons from Libya.
While he was widely regarded as a hero in republican circles, to the unionist and Protestant community he was despised for directing the republican campaign of violence.
In later years, when the peace process was in its infancy, his support
for the leadership of Gerry Adams was critical to persuading many
republican doubters both in Northern Ireland and in the United States.
In 1998, Cahill urged republicans to endorse the Good Friday Agreement and he was an honorary life vice-president of Sinn Fein.
In one of his last public appearances, Cahill spoke at Sinn Fein's annual conference last year.
To wild cheers, he told his fellow republicans: "We've won the war, now let's win the peace."
Party leader Gerry Adams said his contribution to Irish republicanism would ensure he was remembered for many generations.
"Joe Cahill spent a lifetime in struggle. He was both a leader and a servant of the republican cause," he said.
"He was an unapologetic physical force republican who fought when he felt that was the only option, but he also significantly stood for peace and was a champion of the Sinn Fein peace strategy, travelling to the US on many occasions on behalf of the party."
Sinn Fein MP Martin McGuinness said he played a key role in the peace process.
"Joe Cahill was in my opinion an uppity working class Belfast fenian who had the temerity to challenge the British system in Ireland and the injustices that that system heaped upon the people that he loved," he said.
Cahill worked in the Belfast shipyard of Harland and Wolff between 1950-51 after being released from prison.
Last year, he announced he was suing the shipbuilders because he was suffering from asbestosis.
Joe Cahill's funeral is due to take place on Tuesday.