About a hundred Irish Republican Army (IRA) volunteers, commanded by Tom Barry, escaped an attempt by about 1,200 British troops to encircle them.

The British succeeded in breaking an IRA volunteer under torture and discovered that the West Cork Brigade had its headquarters in Ballymurphy.

[2] The British commanders thus planned a major operation to capture the IRA column, mobilising about 350 troops in total, to converge on the area from several different directions.

[5] Two more British units converging on the area from the southeast tried to dislodge the IRA from their ambush position, but again without success and they too fled in disorder.

Taking the chance offered by his quick victory to get away, Barry then marched his men to safety in the Gurranereigh area, while the British were still disoriented by the ambush.

On realising what had happened, Major Percival of the Essex Regiment rushed to the scene with his troops, but was only able to open a long range fire on the fleeing IRA men.

He later blamed the failure of the British operation on the Auxiliary column which had gone to the wrong rendezvous point and had therefore left a gap in the encirclement.

Volunteer Tom Kelleher—a Section Leader in Barry's column— claimed that he alone personally shot and either killed or wounded 22 British soldiers during the fire-fight.

[7] According to historian Peter Hart, the figure of 10 Crown forces personnel killed and four wounded, was "given in internal police and military documents and verified at the inquest",[11][12] Historian Michael Hopkinson concludes of the action, "With considerable justice, Crossbarry is regarded as victory for the IRA, but can also be seen as a missed opportunity for the British".