On 14 April 1922 a column of 200 men led by Rory O’Connor occupied the Four Courts, hoping to provoke an armed confrontation with British forces which were in the process of evacuating from Ireland following the signing of the Anglo-Irish Treaty the previous winter which had split the IRA into two opposing factions. The occupation was a direct challenge to the legitimacy of the Provisional government who sought a smooth transition to a viable independent Irish state in the 26 counties of southern Ireland.

On 22 June Field Marshall Sir Henry Wilson was gunned down by two IRA assassins and on 26 June, the Free State Army Deputy Chief of Staff General J.J. O’Connell was kidnapped by the Four Courts IRA garrison. Collins had also shipped guns issued by the British to arm the new Irish Army to Northern IRA units to defend themselves from loyalists.

Michael Collins, no longer able to resist British pressure, received two 18 pounder artillery guns and a stock of 200 artillery shells from the store at Kilmainham and the guns were set up at Parliament Street and Winetavern Street and Bridgefoot Street and Usher’s Quay across the Liffey from the facade of the heavily fortified Four Courts where the Anti-Treaty IRA had barricaded themselves. Free State troops established a cordon around the building, closing streets and riflemen and machine gunners occupied windows and rooftops. Among the IRA leaders inside were Chief-of-Staff Joe McKelvey, Director of Engineering Rory O’Connor, Quarter Master General Liam Mellows, commander of the IRA’s 2nd Southern Division Ernie O’Malley, Commandant Paddy O’Brien, Commandant Tom Barry and many others. The IRA mostly drawn from 1st and 2nd Battalions of the 1st Dublin Brigade were armed with rifles, five Thompson submachine guns and two Lewis machine guns as well as an armoured car nicknamed “The Mutineer.”

The bombardment began on 28 June as artillery guns supervised by Emmet Dalton began blasting the Four Courts at point-blank range every fifteen minutes from across the Liffey. The complex of buildings also came under a hail of rifle and machine gun fire. However the strong stone walls of the 18th century Four Courts held out. A number of the shells overshot their target and landed near General McCready’s British Army HQ. IRA leader Ernie O’Malley later claimed to have witnessed a gun crew fighting a duel with a sniper in the dome of the courts. The failures of the first day led the impatient British to offer two more 18 pounders as well as heavy howitzers and aircraft in order to destroy the Four Courts once and for all.