In his absence, two young men, Michael Collins and Richard Mulcahy rose to prominence as the clandestine leaders of the IRA – respectively Director of Intelligence and Chief of Staff of the guerrilla organisation.
The British team led by David Lloyd George and Winston Churchill were prepared to make concessions on Irish independence but would not concede a republic.
The pro-Treaty leadership of Michael Collins and Arthur Griffith, organised in a Provisional Government, set about establishing the Irish Free State created by the Treaty.
[23] O'Connor in April led the occupation by anti-Treaty forces of several public buildings in Dublin, notably the Four Courts – centre of the Irish legal system.
[28] The death in action of Liam Lynch in this month led to the anti-Treaty IRA, under the orders of Frank Aiken and on the urgings of civilian leader de Valera, calling a ceasefire and to "dump arms".
The Cumann na nGaedheal governments, led by WT Cosgrave, were highly conservative – being more concerned with establishing the state's basic institutions after the havoc of the Civil War than with social or political reform.
One of the major successes of the Cumann na nGaedheal governments was to establish the police, the Garda Síochána, as an unarmed and politically neutral force, relatively untainted by the bitterness of the civil war.
While the last prisoners of the Civil War were released in 1924, the Free State retained extensive emergency powers to intern and even execute political opponents, under a series of Public Safety Acts (1923, 1926 and 1931).
The political representatives of the anti-Treaty side had re-grouped in 1926 as Fianna Fáil, leaving only a minority of intransigent republicans in Sinn Féin and the IRA who refused to recognise the legitimacy of the state.
Fianna Fáil won the 1932 election on a programme of developing Irish industry, creating jobs, providing more social services and cutting the remaining links with the British Empire.
This greatly antagonised pro-Treaty Civil War veterans, who in response formed the quasi-fascist Blueshirts (initially the "Army Comrades Association"), led by the former Garda Commissioner Eoin O'Duffy to oppose the IRA.
Not long afterwards, in 1936, de Valera made a clean break with political violence when he banned the increasingly left-wing IRA after they murdered a landlord's agent, Richard More O'Farrell, in a land dispute and fired shots at police during a strike of Tramway workers in Dublin.
Instead of free trade, which benefited mainly substantial farmers, Fianna Fáil pursued the nationalist aim of establishing Irish domestic industries, which were protected from foreign competitors by tariffs and subsidies.
The parliament of the UK passed The Statute of Westminster 1931, which granted legislative independence to the six Dominions, Australia, Canada, the Irish Free State, Newfoundland, New Zealand, and South Africa.
However, in 1969, the Irish government found itself placed in a very difficult position when conflict erupted in Northern Ireland in the form of rioting in Derry, Belfast and other urban centres.
Two episodes in particular caused concern – the Battle of the Bogside in Derry, in which nationalists fought the police for three days and the rioting in Belfast, in which several Catholic neighbourhoods were attacked and burned by loyalists.
Taoiseach Jack Lynch in a televised address, said, "we can not stand by and watch innocent people being injured and perhaps worse", comments taken to mean that Irish troops would be sent over the border to assist Northern nationalists.
The Irish government also refused to allow British and Northern Ireland security units to pursue Republican paramilitaries over the border into the Republic and arrested those soldiers or police who did enter its territory armed.
However, the PIRA successfully used the South as a safe haven in order to sustain its campaign against the British in Northern Ireland, widely owing to the sympathy of the Southern Irish population.
Many were involved in the GAA or other local organisations and their neighbours could, to paraphrase [Irish writer Tim Pat] Coogan, quietly and approvingly mutter about the 'boys' – and then go off without a qualm the next day to vote for a political party aggressively opposed to the IRA.
"[43] Shannon Airport and Cork and Cobh harbours were used extensively by the IRA for arms importation overseas during the early 1970s aided by sympathetic workers on-site.
The second factor was getting public spending under control by a series of agreements, termed 'social partnership' with the trade unions – where gradual increases in pay were awarded in return for no industrial action.
This debt, now estimated at over €50 billion, (over half of which will be paid to Anglo Irish Bank) imposed a heavy burden on the tax-payer and severely damaged Ireland's ability to borrow money from the International Bond markets.
Under pressure from the European Union, which feared a 'run' (selling causing a collapse in value) of the euro, Ireland was forced to accept a 16-year loan of €85 billion at just under 6% interest from IMF and EU itself.
[61] Not only were the interest rates of the loan high, but the deal also involved a humiliating loss of sovereignty, in which Irish budgets had to first be approved by other parliaments of the EU – notably that of Germany.
The political result of this crisis was the fall of the Cowen government and a shattering defeat for Fianna Fáil in the 2011 Irish general election, in which the party won just 17% of the vote and retained only 20 out of its 71 seats in the Dáil.
[66] International news outlets described the result as a historic break from the two-party system, as it was the first time in almost a century that neither Fianna Fáil nor Fine Gael won the most votes.
Liberalisation has been championed by figures like Mary Robinson, a radical feminist senator who became President of Ireland, and David Norris, who led the Campaign for Homosexual Law Reform.
In the 1980s and early 1990s, these questions were deeply divisive in the Republic of Ireland and exposed deep social cleavages between religious and secular-minded people, urban and rural, middle and working classes.
[81] The Beef Tribunal in the early 1990s found that major food companies, notably in Iraq had been given preferential treatment by the Fianna Fáil government in return for donations to that party.