O'Connell, Jeremiah Joseph (‘J. J.’, ‘Ginger’) (1887–1944), soldier and revolutionary, was born 21 December 1887 in Ballina, Co. Mayo, son of Jeremiah Ambrose O'Connell, national school inspector, and Winifred O'Connell (née Geraty). Because of his father's job the family moved frequently and lived in Sligo, Derry, Longford, and Belfast. Educated at the Mercy convent, Sligo, at Moyola Park national school, Castledawson, Co. Londonderry, at St Mel's College, Longford, and at Clongowes Wood College, Co. Kildare (1903–5), he received a BA and a first-class MA from UCD, where he was active in student affairs as a committee member of the Literary and Historical Society and trainer of the boxing team. Nicknamed ‘Ginger’ because of his red hair, he was so known throughout his life.
Having served two years in the US army (1912–14), attached to the 69th (New York) Regiment, he returned to Ireland and during 1915–16 was chief of inspection for the Irish Volunteers, during which he travelled throughout the country organising Volunteer corps, delivered lectures on military tactics to Volunteers and Fianna Éireann, and contributed to the Irish Volunteer journal. He also delivered a series of lectures on famous Irish battles to the Gaelic League in Dublin, and at the request of Bulmer Hobson (qv) drafted a memo on how the Volunteers could best undertake war. He was not a member of the IRB, believing soldiers should not join secret societies. In 1916 he conveyed the countermanding order from Eoin MacNeill (qv) to Volunteers in Cork in an effort to stop the rising. Although he took no part in the fighting he was arrested and imprisoned in Frongoch (April–July 1916), where he was commandant of South Camp, and Reading (July–December 1916). An instructor (1917–19) with the Sligo Brigade, Irish Volunteers, he was imprisoned in 1918 for alleged involvement in the fabricated ‘German plot’. Made assistant director of training in 1919, he succeeded Dick McKee (qv) as director of training in November 1920, in which capacity he contributed ‘Notes on training’ to the Volunteer journal An tÓglach. During the treaty negotiations (October–December 1921), he attended conferences in London dealing with defence questions relating to the negotiations. A supporter of the treaty, he was made deputy chief of staff in the national army in 1922 with responsibility for building the new force. Taking a hard-line approach to the anti-treaty IRA, he opposed the level of concessions made to them in the unsuccessful army unification talks in May 1922, and felt that allowing their forces to remain in occupation of barracks in Limerick city was a sell-out. His kidnapping in Dublin on 27 June 1922 by anti-treaty IRA from the Four Courts garrison, in reaction to the arrest of Leo Henderson, was one of the events that led to the army's attack on the Four Courts and the start of the civil war. Released when the garrison surrendered on 30 June, O'Connell was GOC Curragh camp and Curragh command during the civil war. During army reorganisation (1922–3) he was demoted first to major-general and later to colonel, the rank that he held for the remainder of his military career.
O'Connell held a number of posts in the national army after independence: chief lecturer in the army school of instruction (1924–9); director of no. 2 (intelligence) bureau (1929–32); OC equitation school (March–June 1932); quartermaster-general (1932–5) and director of the military archives (1935–44). In 1940 he was detailed to draw up general defence plans and suggest proposals for possible military action by the Irish army in the event of invasion. In an article published in Studies in March 1938 he had warned of the dangers of air attack and urged the preparation of black-out and evacuation procedures. A military historian, he published numerous articles on Irish and foreign military history and tactics.
He married (19 October 1922) Gertrude McGilligan of Coleraine, Co. Londonderry, daughter of Patrick McGilligan (businessman and anti-Parnellite nationalist MP for Fermanagh South 1892–5) and Catherine McGilligan (née O'Farrell), and sister of the politician and lawyer Patrick McGilligan (qv). They had one son and one daughter and lived in married officers' quarters in the various barracks where he was stationed. He died 19 February 1944 in the Richmond hospital, Dublin, having suffered a heart attack, and left an estate of £1,101. His papers are in the NLI.