Peadar O'Donnell was born into an Irish speaking family in Dungloe, County Donegal in northwest Ireland, in 1893. He attended St. Patrick's College, Dublin, where he trained as a teacher. He taught on Arranmore Island off the west coast of Donegal before spending time in Scotland.
By 1919, he was a leading organiser for the Irish Transport and General Workers' Union. He also attempted in Derry to organise a unit of the Irish Citizen Army (a socialist militia which had taken part in the Easter Rising). When this failed to get off the ground, O'Donnell joined the Irish Republican Army (IRA) and remained active in it during the Irish War of Independence (1919-1921). He led IRA guerrilla activities in County Londonderry and Donegal in this period, which mainly involved raids on Royal Irish Constabulary and British Army barracks. In 1921, he became the commander of the IRA's Donegal Brigade. He became known in this period as a headstrong and sometimes insubordinate officer as he often launched operations without orders and in defiance of directives from his superiors in the IRA. In the spring of 1921, O'Donnell and his men had to evade a sweep of the county by over 1000 British troops.
After the Anglo-Irish Treaty of 1922, O'Donnell and his IRA comrades were split over whether to accept this compromise, which ended their hopes of an Irish republic but which granted a self governing Irish Free State. O'Donnell opposed this compromise and in March 1922, was elected, along with Joe McKelvey as a representative for Ulster on the anti-Treaty IRA's army executive. In April he was among the anti-Treaty IRA men who took over the Four Courts building in Dublin and helped to spark the outbreak of civil war with the new Free State government. The Irish Civil War would rage for another nine months. O'Donnell escaped from the Four Courts building after its bombardment and surrender, but was subsequently captured by the Free State forces, and imprisoned in Mountjoy Gaol. At the end of the Civil War, he participated in the mass Republican hunger strike that was launched in protest at the continued imprisonment of Anti-Treaty IRA men, resisting in this manner for 41 days.
Unlike most Irish republicans of this era, O'Donnell did not see the republican cause solely in Irish nationalist terms. O'Donnell also advocated a social revolution in an independent Ireland, seeing himself as a follower of James Connolly, the socialist republican executed for his part in the Easter Rising. The period 1919-1923 had seen much social unrest in Ireland, including land occupations by the tenants in rural areas and the occupation of factories by workers. O'Donnel, in fact, is regarded as the first Irish person to use the term "occupation" in relation to the occupation of a workplace when he and the staff of Monaghan Asylum occupied the hospital in 1919.
"The occupation was, in fact, the first action in Ireland to describe itself as a soviet and the red flag was raised above it."O'Donnell believed that the IRA should have adopted these people's cause and supported land re-distribution and workers' rights. He blamed the anti-Treaty republicans' lack of support among the Irish public in the Civil War on their lack of a social programme. Some republicans, notably Liam Mellows, did share O'Donnell's view, but they were a minority.
According to author and historian Tom Mahon,
"There were many contradictions and weaknesses in O'Donnnell's polemic. In reality, the IRA was a Petite bourgeoisie conspiratorial organisation rather than a workers' and peasants' army. It was firmly routed in the nineteenth century concept of a nationalist revolution and its few socialists were largely peripheral to the organisation. Kevin O'Higgins, a leading Sinn Fein activist during the Anglo-Irish War, famously said, 'We were probably the most conservative-minded revolutionaries who ever put through a successful revolution.' Additionally, O'Donnell failed to justify the IRA's refusal to acknowledge the wishes of the majority of the southern Irish population who supported the Free State. Most glaring of all, he had no satisfactory explanation of what to do with the Protestant working-class in Northern Ireland, who were prepared to take up arms to prevent their 'liberation' by the IRA. Despite the many flaws of his argument, he has received much serious attention from historians and biographers."In 1923, while still in prison, he was elected Teachta Dála for Donegal as a Sinn Féin candidate. In 1924, on release from internment, O'Donnell became a member of the Executive and Army Council of the anti-Treaty IRA. He tried to steer it in a left-wing direction, and to this end founded organisations such as the Irish Working Farmers' Committee, which sent representatives to the Soviet Union and the Profintern. O'Donnell also founded the Anti-Tribute League, which opposed the repaying of annuities to the British government owed since the Irish Land Acts. He also founded a short-lived socialist republican party, Saor Éire.
In addition, O'Donnell and the IRA found themselves in conflict with their former enemies of the Civil War era. Éamon de Valera, who had founded Fianna Fáil from anti-Treaty republicans, came to power in Ireland in 1932, and subsequently legalised the IRA in 1932-36. O'Donnell announced that there would be "no free speech for traitors" (by which he meant Cumann na nGaedheal, the Free State party) and his men attacked Cumann na nGaedheal political meetings. In response, Eoin O'Duffy, a former Irish army General and Garda Síochána commissioner, founded the Blueshirts (a semi-fascist organisation, originally named the Army Comrades Association) to resist them. There was a considerable amount of street violence between the two sides before both the Blueshirts and then the IRA became banned organisations. O'Donnell saw the Blueshirts as a fascist movement based on the big farmer class.
O'Donnell's attempts at persuading the remnants of the defeated anti-Treaty IRA to become a socialist organization ended in failure. Eventually, O'Donnell and other left-wing republicans left the IRA to found the Republican Congress in 1934. However, this organisation made little impact in Irish politics.
O'Donnell happened to be in Barcelona attending the People's Olympics on the outbreak of the Spanish Civil War in 1936. He joined the Spanish Republican militia that supported the Popular Front government against Francisco Franco's military insurgency. When he returned to Ireland, he encouraged other republicans to fight for the Spanish Republic - accordingly, IRA men, led by Frank Ryan and some Communist Party of Ireland members joined the International Brigades, where they were known as the Connolly Column (after James Connolly).
This was a very unpopular stance in Ireland, as the powerful Roman Catholic Church strongly supported Franco's Catholic Nationalists. Attitudes to the Spanish Civil War also mirrored the divisions of Ireland's civil war. O'Donnell remarked that the Bishops had condemned the anti-Treaty side in the latter for opposing a democratic government, but were now advocating the same thing themselves. A former comrade of O'Donnell's, Eoin O'Duffy, led an Irish Brigade (Spanish Civil War) to fight for the Nationalists.
After the 1940s, O'Donnell devoted more of his time to writing and culture and less to politics, from which he withdrew more or less completely. He published his first novel, Storm, in 1925. This was followed by Islanders (1928), Adrigool (1929), The Knife (1930) and On the Edge of the Stream (1934). O'Donnell also went to Spain and later published Salud! An Irishman in Spain (1937).
After World War II, he edited the Irish literary journal, The Bell (1946-54). Other books by O'Donnell include The Big Window (1955) and Proud Island (1975). He also published two volumes of autobiography, The Gates Flew Open (1932) and There Will be Another Day (1963).
His one play, Wrack, was first performed at the Abbey Theatre in Dublin on 21 November 1932, and published by Jonathan Cape the following year.
Islanders and Adrigoole were translated into Ulster Irish (Donegal dialect) by Seosamh Mac Grianna as Muintir an Oileáin and Eadarbhaile, respectively. All of his work has a strong social consciousness and works like Adrigoole, as well as being powerful works in themselves, exemplify socialist analyses of Irish society.