Inside the building were 12 members of the Irish Republican Army Executive, including Chief-of-Staff
Joe McKelvey, Director of Engineering Rory O'Connor, Quartermaster General
Liam Mellows and Director of Operations
Ernie O'Malley. The garrison consisted of roughly 180 men drawn from the 1st and 2nd Battalions of the IRA's 1st Dublin Brigade, commanded by Commandant Paddy O'Brien, armed for the most part only with small arms (rifles, five
Thompson submachine guns and two
Lewis light machine guns) apart from one captured
armoured car, which they named "The Mutineer". The members of the IRA Army Executive were the political leaders of the garrison, but served as common soldiers under the command of O'Brien. The Anti-Treaty side fortified the Four Courts to some extent, planting mines around the complex and barricading the doors and windows, but their leadership ordered them not to fire first, in order to retain the moral high ground, and so the Free State troops were allowed to surround the Four Courts. After the first day's bombardment proved ineffective, the British gave the Free State two more 18-pounder cannon and proffered
BL 60-pounder guns along with an offer to bomb the Four Courts from the air. Collins turned down the latter two offers because of the risk of causing heavy civilian casualties. On the 29th, Free State troops stormed the eastern wing of the Four Courts, losing three killed and 14 wounded and taking 33 prisoners. The republicans' armoured car, "The Mutineer", was disabled and abandoned by its crew. Early the next day O'Brien was injured by
shrapnel and O'Malley took over military command in the Four Courts. By this time the shelling had caused the Four Courts to catch fire. In addition, orders arrived from
Oscar Traynor, the anti-treaty IRA commander in Dublin, for the Four Courts garrison to surrender, as he could not reach their position to help them. O'Malley ruled this order invalid, as the Four Courts was a GHQ operation. However, in view of the rapidly deteriorating situation, at 3:30 p.m. on 30 June, O'Malley surrendered the Four Courts to Brig. Gen.
Paddy Daly of the Free State's
Dublin Guard unit. Three of the republican garrison had died in the siege.
Public Record Office explosion Several hours before the surrender, at either 11:30 or 2:15 the
Irish Public Record Office (PRO) block located in the western block of the Four Courts, which had been used as an ammunition store by the Four Courts garrison, was the centre of a huge explosion, destroying Irish state records going back to the
Norman conquest. Forty advancing Free State troops were badly injured. The Irish republican women's paramilitary organisation (
Cumann na mBan) leader
Maire Comerford recalled being blown backwards and forward by the intense blast. Assigning blame for the explosion remains controversial. It was alleged by the National Army Headquarters that the Anti-treaty forces deliberately booby-trapped the PRO to kill advancing Free State troops.
Tim Healy, a government supporter, later claimed that the explosion was the result of land mines, laid before the surrender, exploding afterwards. In contrast, a 2018 study by Michael Fewer found no evidence that the IRA had set off an explosion. This study suggests that the explosion originated from fires, caused by the Four Courts being shelled, which ultimately reached explosive materials stored in the PRO. A towering
mushroom cloud rose over the Four Courts.
Calton Younger identified three explosions: "two beneath the Records Office at about 2.15 [pm] and another at the back of the building at about 5 o'clock". At this stage in the battle troops on each side still had a sense of kinship with the other, as most of them had fought together in the
Irish Republican Army during the
Irish War of Independence. 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. 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. The
National Archives of Ireland and
Irish Manuscripts Commission have assembled and published original documents from other sources to mitigate the loss. 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. ==O'Connell Street fighting==