Mr Sean Mac Stiofain, who died yesterday aged 73, was the Provisional IRA chief-of-staff from 1969 to 1972 and directed the campaign of violence in Northern Ireland during those years.
Yesterday, Sinn Fein President Mr Gerry Adams MP said Mr Mac Stiofain would be "missed by republicans everywhere. He played a leading role throughout his life in the struggle for social justice and a united Ireland.
"Those of us who were privileged to know him well will mourn his passing deeply."
Mr Ruairi O Bradaigh of Republican Sinn Fein described Mr Mac Stiofain as "a giant of a man in the republican movement".
Mr Mac Stiofain was born and reared in England, the only child of a Belfast Protestant mother and atheistic father.
In October 1953, a Hertfordshire court sentenced John Stephenson, then 24, an ex-RAF corporal, to eight years for helping to break into Felsted School in Essex and stealing firearms from the cadet force. Another of those sentenced was Cathal Goulding.
When John Stephenson came out of Wormwood Scrubs six years later, it was as Sean Mac Stiofain. He learned fluent Irish while in jail and studied the Irish situation.
He moved to Ireland and joined Mr Goulding who had just been chosen as chief-of-staff of the official IRA, but there were differences in ideology between them. While Mr Goulding began to lead the movement away from violence, Mr Mac Stiofain, a practising Catholic, non-smoker and non-drinker, clung to the old doctrine of a reunited Ireland by the use of the gun.
After the division, which came into the open at the end of 1969 when British troops went to the North, Mr Mac Stiofain worked in Navan, Co Meath, as head of the Provisional army council.
In November 1972, Mr Mac Stiofain was charged in the Special Criminal Court with being a member of an unlawful organisation and sentenced to six months. He began a hunger strike and was moved to the Curragh Military Hospital. It lasted 58 days, ending in January 1973. He was released in April that year.
In November 1981, Mr Mac Stiofain resigned from Provisional Sinn Fein following the organisation's decision to drop its policy supporting a federal Ireland.
Mr Mac Stiofain died in Our Lady's Hospital, Navan, after a long illness. The removal will be from Fitzsimons Funeral Home in Navan town tomorrow at 7 p.m. to St Mary's Church. On Monday, the funeral Mass will be at 12.30 p.m. followed by burial in St Mary's Cemetery.
Mr Mac Stiofain is survived by his wife, Maire, and two daughters.