Richard Mulcahy Papers, P7/A/23 (UCDA). In the Diary of the Fourth (Midleton) Battalion of the Cork No. 1 Brigade for June 1921, there appeared the following phrase about B and D Companies of that battalion: ‘2 enemy spies, J. J. Walsh, Midleton, and M[ichae]l Callaghan, Carrigtwohill, shot. Latter believed to be of importance.’ The IRA certainly believed that O'Callaghan was identifying Volunteers to Crown Forces. He appears to have been in Fleet Auxiliary, but left by 1911. At the time of his death he was employed at the Dockyard at Haulbowline.
Thomas Cotter, a lieutenant in the Carrigtwohill IRA Company, later claimed responsibility for executing O’Callaghan as a spy. See Sheehan (2011), 76. Cotter named his associates in executing O’Callaghan as Volunteers Harry O’Brien of the IRA First Southern Division Engineers unit; M. McCarthy of E Company (Knockraha) of the 4th Battalion; and P. Mahony of Anngrove (Carrigtwohill). See Seámus Fitzgerald Papers, PR/6/32 (2), (UCC).
1886 Born I cannot get a birth certificate
1901 census at Carrigtohill
1911 census at Carrigtohill. He is already descibed as a Royal Fleet Reserve Pensioner
1921 Jun 21 Shot in Cork
Compensation Claim. British liability was accepted, and £600 was awarded. See Register of Compensation Commission (Ireland) Cases of Private Persons (CO 905/15, TNA).