About 200 Anti-Treaty Irish Republican Army militants led by Rory O’Connor occupy the Four Courts in the centre of Dublin on April 14, 1922 in defiance of the Provisional Government. They intend to provoke the British troops, who are still in the country, to attack them, which they believe will restart the war with Britain and re-unite the Irish Republican Army against their common enemy. They also occupy other smaller buildings regarded as being associated with the former British administration, such as the Ballast Office and the Freemasons’ Hall in Molesworth Street, but the Four Courts remains the focus of interest. On June 15, O’Connor sends out men to collect the rifles that belong to the mutineers of the Civic Guards.
Winston Churchill and the Cabinet of the United Kingdom apply pressure on the Provisional Government to dislodge the rebels in Four Courts, considering their presence there as a violation of the Anglo-Irish Treaty. Michael Collins, President of the Provisional Government Cabinet, tries desperately to persuade O’Connor and his men to leave the building over the next three months. At the Third IRA Convention, the executive is split over whether the Irish Government should demand that all British troops leave within 72 hours. The motion is defeated, but the IRA splits into two factions opposed to the government, one conciliatory, led by Liam Lynch, Sean Moylan, and Liam Deasy, and the other less moderate, led by Tom Barry and Joe McKelvey.
During the month of June 1922, the Provisional Government engages in intense negotiations with the British Cabinet, seeking to diffuse the threat of imminent civil war. However, the conservative British Cabinet refuses to cooperate.
On June 22, 1922, arch-Unionist Sir Henry Wilson is assassinated by two IRA men, both former British soldiers, Reginald Dunne and Joseph O’Sullivan. It is considered by some that this is done on the orders of Michael Collins, who has been a close friend of Dunne in the London Irish Republican Brotherhood. David Lloyd George writes an angry letter to Collins which includes the line “…still less can Mr. Rory O’Connor be permitted to remain his followers and his arsenal in open rebellion in the heart of Dublin… organizing and sending out from this centre enterprises of murder not only in the area of your Government…”
On June 28, 1922, after the Four Courts garrison has kidnapped J.J. “Ginger” O’Connell, a general in the new Free State Army, Collins begins shelling the Four Courts with borrowed British artillery. O’Connor and 130 men surrender on July 3 and are arrested and imprisoned at Mountjoy Prison. This incident sparks the Irish Civil War as fighting breaks out around the country between pro and anti-treaty factions.