During the Easter Rising O'Hegarty was stationed in Ballingeary when visited by Michael McCarthy of Dunmanway to propose an attack on an RIC post at Macroom.

[citation needed] One such was battalion commander, Richard Langford, who joined with O'Hegarty's unit to make an unauthorized raid on the RIC post at Macroom.

The coroner blamed the British establishment in Dublin, but the police never made any attempt to investigate the killings.

[6] The brigade commanders in the southern division retained a residual lingering resentment of Dublin GHQ's lack of leadership and supplies.

At a meeting set up for 26 April 1921, when the manual of Infantry Training 1914 was produced it, the document, raised great anger.

The meeting ended in uproar, when O'Hegarty who was "a master of invective, tore the communication and its authors to ribbons".

[7] O'Malley and Liam Lynch, the general, met with O'Hegarty in the mountains of West Cork, near a deserted farmhouse, just off the main road.

"[8] In the retreat that followed, the Irish lost heavy casualties, and left their wounded to the good care of the British.

He was ruthless in the treatment of Mrs Georgina Lindsay and her chauffeur who gave away information to the Catholic clergy, but remarkably lenient on brigade traitors within.

Like the commanders De Valera rejected the treaty, but had already been defeated in the Dáil on a vote by Cosgrave's majority.

[10] On 1 February 1922, O'Hegarty married Maghdalen Ni Laoghaire (d.1940), who was a prominent member of Cumann na mBan.

These men included Tom Barry, Liam Mellows, and Rory O'Connor, who were all in favour of continuing the fight until the British were driven out of Ireland altogether.

In a letter to Jim Donovan (Seamus O'Donovan) on 7 April he blamed Hegarty for all this compromise and "peace talk".

[14] It has been alleged by the author Gerard Murphy that Hegarty had a role in the assassination of the Commander in Chief, Michael Collins in August 192,.

It is alleged that as members of the 1st Southern Division Cork they were actually feigning claims of neutrality but remained part of the IRB in order to set up talks towards peace and the cessation of hostilities at the start of the Irish Civil War.

On forming the Neutral Group of the IRA in December 1922, he tried to unify differences in the volunteers between Republicans and the Free Staters.

He communicated with the Papal Nuncio during the inter-war years in an attempt to have Bishop Cohalan's excommunication bull lifted.

Instead he turned to commemoration as a way to earn favour in Rome, with the dedication of a catholic church in Finnbarr's cemetery.