The Clonmult ambush takes place on February 20, 1921, during the Irish War of Independence.

Irish Republican Army (IRA) volunteers occupying a farmhouse in Clonmult, County Cork are surrounded by a force of British Army, Royal Irish Constabulary (RIC) and Auxiliaries. In the action that follows, twelve IRA volunteers are killed, four wounded and four captured. A total of 22 people die in the ambush and subsequent executions – fourteen IRA members, two Black and Tans and six suspected informers.

The 4th battalion of the IRA First Cork Brigade, under Diarmuid O’Hurley and based around Midleton, Youghal and Cobh, had been a successful unit up until the Clonmult ambush. They had captured three RIC barracks and carried out an ambush in Midleton itself. In January 1921, the unit takes possession of a disused farmhouse overlooking the village of Clonmult. O’Hurley plans to ambush a military train at Cobh Junction on Tuesday, February 22, 1921 and at the time of the Clonmult action is scouting a suitable ambush site. However, according to historian Peter Hart, they “had become over-confident and fallen into a traceable routine.” An intelligence officer of the British Army Hampshire Regiment traces them to their billet at a farmhouse in Clonmult.

British troops, a party of the 2nd Battalion, Hampshire Regiment under the command of Lieutenant A. R. Koe, surround the house. Two IRA volunteers notice the advancing troops and open fire. Both are killed, but the shooting warns those sheltering inside the house, and a siege begins. A sortie from the house is attempted in the hope of gaining reinforcements from the local IRA company.

The acting IRA commander, Captain Jack O’Connell, manages to get away but three other volunteers are killed in the attempt. But O’Connell is unable to bring help in time. The Volunteers trapped inside make a desperate but unsuccessful attempt to escape through a narrow opening in the gable. Their hopes are dashed when British reinforcements arrive instead — regular RIC police, Black and Tans and Auxiliaries. The police also bring petrol, which an Army officer uses to set the thatched roof of the farmhouse on fire. With the farmhouse burning around them, an attempt is then made by the IRA to surrender.

What happens next is disputed. In his after-action report, Lieutenant Koe reports that at 6:30 PM six or seven rebels come out of the house with their hands up. As the Crown Forces go to meet them the remaining rebels in the house open fire. Some of the rebels outside the house are killed or wounded by the crossfire that ensues. The Crown Forces rush the house and the eight rebels inside are taken prisoner. By contrast, the surviving Volunteers claim that their men had surrendered in good faith, and had come out with their hands up, only to be shot by the police without any provocation. Opinion is divided amongst historians as to which version of the story to believe.

A total of twelve IRA Volunteers are killed in the action, with four more wounded and only four taken prisoner unscathed. Two of the IRA prisoners, Maurice Moore and Paddy O’Sullivan, are later executed in the Cork military barracks on April 28. Patrick Higgins, an IRA man who survived the killings, is sentenced to death but is reprieved due to the truce that ends the war on July 11. Hampshire Regiment historian Scott Daniell notes on the action that “like all the Irish operations, it was hateful to the British troops.”

The IRA suspects that an informer had led the British to the billet of the column wiped out at Clonmult, and over the following week, six alleged spies are executed by the IRA in the surrounding area. Mick Leahy, a local IRA officer, states that “things went to hell in the battallion” after Clonmult. Diarmuid O’Hurley, the commander of the battalion, is not at Clonmult but is later killed on May 28, 1921.