The Battle of Ballynahinch was fought outside Ballynahinch, County Down, on 12 June, during the Irish rebellion of 1798 between British forces led by Major-General George Nugent and the local United Irishmen led by Henry Munro.
Munro was a Lisburn linen merchant and Presbyterian United Irishman who had no military experience but had taken over command of the Down organisation following the arrest of the designated leader, Rev. William Steel Dickson on 5 June.
Upon hearing of the victory at Saintfield on 9 June, Munro joined the rebel camp there and then moved to Ednavady Hill, Ballynahinch to join the thousands who had gathered in support of the rebellion. The response of the British garrisons was to converge on Ballynahinch from Belfast and Downpatrick in two columns accompanied by several pieces of cannon.
The battle began on the night of 12 June when two hills to the left and right of Ballynahinch were occupied by the British who pounded the town with their cannon. During a pause when night fell, some rebel officers were said to have pressed Munro for a night attack but he refused on the grounds that it was unchivalrous. As a consequence many disillusioned rebels slipped away during the night.
As dawn broke the battle recommenced with the rebels attacked from two sides and although achieving some initial success, confusion in the rebel army saw the United Irishmen retreat in chaos, pursued by regrouping British forces who quickly took advantage by turning retreat into massacre. Initial reports claimed four hundred rebels were killed, while British losses were around forty.James Thomson (mathematician), the father of the famous scientist William Thomson, 1st Baron Kelvin was at the battle and published an eyewitness account.
Munro escaped the field of battle but was betrayed by a farmer who he had paid to conceal him and was hanged in front of his own house in Lisburn on 16 June. Ballynahinch was sacked by the victorious military after the battle with sixty-three houses being burned down. Cavalry scoured the surrounding countryside for rebels, raiding homes and killing indiscriminately, the 22nd Dragoons being guilty of some of the worst atrocities.The most famous victim was Betsy Gray,
a young female rebel who, with her two brothers, was slaughtered in the post-battle massacre, ensuring her place in legend to this day.
Because of his family’s involvement in this event, Robert Stewart, the future Lord Castlereagh, was made chief secretary of Ireland.