The battle began as an attempt to finish what the fall of Limerick city had started. Anti-Treaty Republican forces under Liam Deasy had held the city for a week in mid-July 1922 before withdrawing south to regroup. They chose well. Bruff, Bruree and Kilmallock - three small towns on three modest hills - sat astride the road to Cork like the corners of a defensive triangle. The Free State army, advancing south, would have to break that triangle or go around it. O'Duffy planned to break it. His second-in-command, Major General W.R.E. Murphy, brought to the planning the cautious instincts of a former lieutenant colonel of the World War I trenches. Their problem was matériel and men. The Free State could muster only about 1,300 rifles in the area; Deasy commanded an estimated 2,000 - many of them seasoned Volunteers from Limerick, Cork and Kerry, armed and angry and unwilling to accept the new Treaty state.

The first clashes went badly for the National Army. On 23 July Free State forces took Bruff, advanced toward Kilmallock, and were beaten back twice by determined Republican resistance. The next day the Republicans counter-attacked, retook Bruff, and captured 76 Free State soldiers as prisoners. O'Duffy called a halt and waited for reinforcements. When the advance resumed, casualties mounted. On 25 July a Dublin Guard unit under Tom Flood was ambushed on a narrow Limerick lane; four men were killed cutting their way through. Two days later three more died. On 30 July Murphy launched his set-piece attack on Bruree itself - Dublin Guards from the southeast, armoured cars in support, an eighteen-pound field gun firing across the fields. The Republicans held for five hours. Then the artillery did its work and the town was taken. Thirteen Free State soldiers and nine anti-Treaty fighters were killed in that one action.

Deasy understood that Bruree was the key to Kilmallock. On 2 August he sent his three improvised armoured cars - hammered-together steel plate on commandeered lorry chassis, mounted with Lewis guns and trench mortars - to retake the town. They achieved tactical surprise. One car charged Commandant Flood's headquarters at the Railway Hotel; Flood and his men shot their way out the back under Lewis gun cover. A second armoured car rammed the front door of a schoolhouse strongpoint; twenty-five Free State soldiers inside surrendered to the steel-clad apparition. For a few hours the counter-attack looked like it might work. Then Free State reinforcements rolled in, led personally by Commandant General Seamus Hogan riding in an armoured car nicknamed The Customs House - one of the captured vehicles from the Battle of Dublin. The Republicans broke off and withdrew. Bruree stayed Free State.

By 3 August the National Army had 2,000 men around Kilmallock, with armoured cars and artillery. Another 700 arrived the next day with another field gun. By Saturday 5 August the town was encircled. Free State artillery three miles off shelled Republican positions on Kilmallock Hill and Quarry Hill until both heights fell. O'Duffy expected a brutal house-to-house fight when his men entered the town. They found, instead, only a Cork rearguard fighting a delaying action. Most of the Republicans had already gone. The reason had nothing to do with the strength of O'Duffy's force. On 2 August Free State seaborne landings had hit the Kerry coast; a similar landing would hit Cork on 8 August. Deasy's army was suddenly being outflanked from the sea. The men holding Kilmallock had to go home - to defend their own villages, before there were no villages left to defend.

The Free State took Kilmallock and the line collapsed. The remaining anti-Treaty fighters retreated toward Charleville and Cork; the National Army's southward push was held briefly at Newcastle West, then resumed. The conventional phase of the Irish Civil War was effectively over. What followed was guerrilla warfare and assassination, ambush and reprisal, until the formal Republican order to dump arms in May 1923. Today the Kilmallock-Bruff-Bruree triangle is quiet farmland, hedgerows and small graveyards. The Friar's Gate Theatre operates in Kilmallock and the medieval town walls draw tourists. But on the headstones in the local cemeteries, dates from 1922 cluster oddly. The men buried beneath some of them had fought together against the British two years earlier. They died fighting each other in the green hills of south Limerick over the meaning of an Irish state.