Anti-Treaty forces led by Rory O’Connor seized the Four Courts. O’Connor, with approximately 200 men under his command. Their hope was that the British army, who were still based in Dublin, would attack them, thereby reigniting the war of independence and perhaps healing the split.
Arthur Griffith, who was the President of Dáil Éireann, wanted to take action immediately to dislodge the rebels from the Four Courts. Michael Collins, the head of the Free State Army, wanted to avoid a civil war at all costs. He negotiated a pact with De Valera to reunite Sinn Féin. The pact held until just before the General Election in June 1922. As a result of the pact’s failure, Collins’ Pro-Treaty Sinn Féin won the majority of the seats. Collins had left the garrison in the Four Courts alone but slowly built up the Free State Army presence in the area. He was still willing to negotiate to avoid a war, but that decision was taken out of his hands.
On 22 June 1922 Sir Henry Hughes Wilson, a retired British Army officer, was assassinated by IRA gunmen in London. It is not clear who ordered the killing, though it is believed that Collins’ had ordered it since Wilson had been a military advisor in Northern Ireland. The British blamed the Anti-Treaty forces in the Four Courts. Collins was told that if he didn’t dislodge them the British Army would. Collins was still reluctant, even after Free State General, JJ O’Connell was abducted and held in the Four Courts. Collins issued a final ultimatum, ordering the garrison to release O’Connell and surrender or he would attack.
Free State troops opened fire on the Four Courts on 28 June 1922, using artillery “loaned” to them by the British. Among the 200 men in the Anti-Treaty garrison were 12 members of the Army Executive including O’Connor, Chief-of-Staff Joe McKelvey, and Quarter Master General Liam Mellows. They were armed with small firearms, mostly shot guns and a few machine guns. They had also placed mines around the perimeter and had barricaded the doors and windows. The first day of bombardment was ineffectual. On the 29th, Free State troops stormed the east end of the building, with the loss of 3 killed and 14 wounded, but took 33 prisoners. By the next day, the Four Courts was on fire. Facing overwhelming odds, Ernie O’Malley, who had taken command of the garrison after the commander Paddy O’Brien was injured, surrendered the Four Courts to the Free State on 30 June. The garrison had lost only 3 men during the bombardment.
Just hours after the surrender, the Public Records Office, located in the western block of the Four Courts, exploded. Forty Free State troops who had been advancing on the position were injured in the explosion. The fire that followed destroyed centuries of irreplaceable documents located in the office. It was alleged that the Anti-Treaty forces deliberately booby-trapped the office to kill Free State troops. The Anti-Treaty leadership vehemently denied this charge, though they did admit that they used the office as a munitions store. It is likely that the fire from the bombardment caused the explosion.
Following the deaths of Collins and Griffith in August 1922, O’Higgins and Cosgrave became the foremost figure of the Free State cabinet. After Collins assassination, a horrific era of tit-for-tat revenge killings ensued. Cosgrave and O’Higgins implemented martial law and enacted the necessary legislation to set up military courts.
Four republicans were the first to be executed by the Free State in October 1922, followed by Erskine Childers in November 1922. On 7 December, Anti-Treaty IRA gunmen shot two TDs, Sean Hales and Pádraic Ó Máille, in Dublin as they were on their way to the Dáil. Hales was killed and O’Máille was seriously wounded. After an emergency cabinet meeting, the Free State government decided on the retaliatory executions of four prominent Republicans, the men captured in the Four Courts: Rory O’Connor, Liam Mellows, Richard Barrett, and Joe McKelvey. The order for execution was given by Minister for Home Affairs in the Free State Government, Kevin O’Higgins. Less than a year earlier, O’Connor had acted as Best Man at O’Higgins’ wedding. Few other stories illustrate better the tragedy of the divisions caused by the Civil War. According to historian, Michael Hopkinson, Richard Mulcahy had pressed for the executions and that Kevin O’Higgins was the last member of the cabinet to give his consent.