His uncle Peter was a member of the Industrial Workers of the World in Butte, Montana, whom Peadar met on trips home to Ireland.

He led IRA guerrilla activities in County Londonderry and Donegal in this period, which mainly involved raids on Royal Irish Constabulary and British Army installations.

O'Donnell opposed this compromise and in April 1922, was elected, along with Joe McKelvey, as a representative for Ulster on the anti-Treaty IRA's Army Executive.

[8] In April he was among the anti-Treaty IRA men who took over the Four Courts building in Dublin, which became the first focus of the outbreak of civil war with the new Free State government.

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 leadership of the Easter Rising.

Some republicans, notably Liam Mellows, did share O'Donnell's view, and in fact, there was a large redistribution of land from absentee landlords to tenants in the new Free State.

Kevin O'Higgins, a leading Sinn Féin 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.

[citation needed] O'Donnell lost a libel case he took against the Dominican published "Irish Rosary" monthly, following articles in the magazine that claimed he was a Soviet agent, and had studied at the Moscow Lenin School.

[17] 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 to the Profintern.

O'Donnell also founded the Anti-Tribute League, which opposed the repaying of annuities to the British government under the Irish Land Acts (these were set at a rate of £3,100,000 a year, a huge cost to the new state; they were ceased by Éamon de Valera on his accession to power in 1932, and in retaliation, the British government declared an Economic War; the payments were resolved in 1938 by an agreement that Ireland would pay Britain £10 million).

On 18 March 1932, the new government suspended the Public Safety Act, lifting the ban on a number of organisations including the Irish Republican Army.

[19] The newly legalized and liberated Republicans began a "campaign of unrelenting hostility" against their former enemies in the Civil War, breaking up Cumann na nGaedheal political meetings and intimidating supporters.

[24] With the demise of the Blueshirts imminent, 186 delegates attended what became the final Republican Congress assembly in Rathmines Town Hall on 29 and 30 September 1934.

He joined the Spanish Republican militia that supported the Popular Front government against Francisco Franco's military insurgency.

O'Donnell's former comrade Eoin O'Duffy, leader of the Blueshirts, led the ultra-Catholic Irish Brigade to Spain to support the Nationalists; they were sent home by Franco.

[29] Still active in the later part of his life, O'Donnell was chairman of the anti-Vietnam War "Irish Voice on Vietnam" organisation which he co-founded with Dan Breen.

This was followed by Islanders (1928, which was published in the US under the title, "The Way it Was With Them"), which received national and international acclaim,[32] The New York Times describing it as a novel of "quiet brilliance and power", conservative London magazine The Spectator "an intensely beautiful picture of peasant life.

"[32] The writer Benedict Kiely recalled meeting a Chicago man in Iowa in 1968 who had never been to Ireland but could describe the landscape of west Donegal, and the ways of its people, in minute detail despite being blind.

Adrigoole was set in Donegal, but based on the real-life story of the O'Sullivans, a Cork family who had all died of starvation in 1927, and is 'by far the gloomiest and most pessimistic of his books'.

'[33] Islanders and Adrigoole were translated into Ulster Irish (Donegal dialect) by Seosamh Mac Grianna as Muintir an Oileáin and Eadarbhaile, respectively.

After World War II, O'Donnell edited, with Róisín Walsh, the literary journal The Bell from 1946 until 1954, having founded it with Seán Ó Faoláin, its first editor, in 1940.

His one play, Wrack, was first performed at the Abbey Theatre in Dublin on 21 November 1932,[35] and published by Jonathan Cape the following year.

Following his escape from Kilmainham jail, Peadar married Cumann na mBan officer Lile O'Donel on 25 June 1924.

[38] Witnesses at Lile and Peadar's wedding included his brother Frank, Sinéad de Valera, Fiona Plunkett of Cumann na mBan and Mary MacSwiney.

[43] The Irish folk-rock band Moving Hearts recorded Tribute to Peadar O'Donnell, written by Dónal Lunny, on their 1985 album The Storm.