In March 1972, Cahill was part of an IRA delegation that held direct talks with the British Labour Party leader Harold Wilson. However, although the IRA called a three-day ceasefire for the talks, no permanent end to violence was agreed upon. Upon his return to Ireland, Cahill was arrested in Dublin by Gardaí and charged with IRA membership. He went on hunger strike for twenty-three days and was subsequently released due to lack of evidence. In November 1972, Cahill became the IRA's chief of staff and held this position until his arrest the following year.