[2] They wanted to spark a new armed confrontation with the British, which they hoped would bring down the Anglo-Irish Treaty, unite the two factions of the IRA against their former common enemy and restart the fight to create an all-Ireland Irish Republic.

Winston Churchill and the British cabinet had been applying pressure on the Provisional Government to dislodge the rebels in the Four Courts, as they considered their presence a violation of the Treaty.

Such pressure fell heaviest on Michael Collins, President of the Provisional Government Cabinet and effective head of the regular National Army.

Collins, a chief IRA strategist during the War of Independence from Britain, had resisted giving open battle to the anti-Treaty militants since they had first occupied Four Courts the preceding April.

[3][4][5] In June 1922 the Provisional Government engaged in intense negotiations with the British Cabinet over a draft Constitution that sought to avert the impending civil war.

They particularly sought to remove the requirement of an oath to the British Crown by all members of the Dublin government, a key point of contention with anti-Treaty partisans.

Following the assassination of Sir Henry Wilson in London on 22 June 1922 and the arrest by Four Courts troops of Free State Army Deputy Chief of Staff Gen. J.J. O'Connell, British pressure on the Provisional Government intensified.

[12] After the first day's bombardment proved ineffective, the British gave the Free State two more 18-pounder cannon and proffered 60-pounder howitzers along with an offer to bomb the Four Courts from the air.

By appealing to friends on the Free State side, several anti-Treaty leaders among the Four Courts garrison, notably Ernie O'Malley and Seán Lemass, escaped from captivity to continue the fight.

[22] The destruction of irreplaceable historical record in the PRO explosion (and the 1921 burning of the Custom House) has impaired Irish historiography; some had been calendared to varying degrees.

A consortium led by Trinity College Dublin is creating the website "Beyond 2022" to provide a "virtual recreation" of the PRO and its contents, in time for the centenary of the explosion.

Additionally, they had an outpost south of the Liffey at the Swan Pub on Aungier St. Oscar Traynor apparently hoped to receive reinforcements from the rest of the country, but only Anti-Treaty units in Belfast and Tipperary replied and both of them arrived too late to take part in the fighting.

Artillery was used to drive the Anti-Treaty fighters out of positions on Parnell St. and Gardiner St., which gave the Free State troops a clear field of fire down O'Connell St.

Cathal Brugha was the last casualty in the battle for Dublin, which had cost the lives of at least 80 people (15 anti-Treaty IRA Volunteers, 29 National Army soldiers, one British Royal Air Force serviceman and 35 civilians) and over 280 wounded.

[citation needed] When the fighting in Dublin died down, the Free State government was left firmly in control of the Irish capital and the anti-treaty forces dispersed around the country.

Round-ups after the fighting resulted in more Republican prisoners and the death of prominent anti-Treaty activist Harry Boland who was shot dead in Skerries, County Dublin on 31 July.

Four of the Republican leaders captured in the Four Courts, Rory O'Connor, Liam Mellows, Joe McKelvey and Richard Barrett, were later executed by the government in reprisal for the Anti-Treaty side's killing of TD (member of Parliament) Seán Hales.