McGuire became a member of the Provisional IRA in July 1971. Three months later, in October 1971, she accompanied
Dáithí Ó Conaill (a leader of the Republican movement, also known as David O'Connell) to the European continent on an arms buying expedition. The expedition came to nothing because it was reported in the British press, and Ó Conaill and McGuire abandoned the mission. She and Ó Conaill had an affair during this trip, although he was married. She, Ó Conaill, and Ó Conaill's wife had a difficult discussion about the issues involved shortly after they returned to Ireland. Provisional IRA bomb attacks in Belfast, on 21 July 1972 (known as
Bloody Friday) killed seven civilians and two soldiers, and left 130 injured. McGuire subsequently decided to leave the Provisional IRA. She was told by the British authorities that if she did so she would receive
Special Branch protection. In the late summer of 1972 she appeared in London and wrote a series of articles for
The Observer, went into hiding, and wrote a book about her experiences in the organisation called
To Take Arms: A Year in the Provisional IRA which was published in 1973. In it she was hostile to
Seán Mac Stíofáin, IRA Chief of Staff at the time she was a member, but remained sympathetic to Ó Conaill, and wished him success in internal struggles against Mac Stíofáin in the Republican movement. ==Political career==