On 7 August of that year, Harry Thornton, a 29-year-old sewage worker from South Armagh was shot and killed by the British Army while staying in a car outside Springfield Road base in Belfast, he and his coworker Arthur Murphy having been mistaken for gunmen.

The incident caused outrage among South Armagh residents, provided the IRA with many new recruits and created a hostile climate where local people were prepared to tolerate the killing of security force members.

Travelling overland in South Armagh eventually became so dangerous that the British Army began using helicopters to transport troops and supply its bases - a practice that had to be continued until the late 1990s.

[12] IRA volunteer Éamon McGuire, a former Aer Lingus senior engineer, and his team claim that they were responsible for getting the British Army "off the ground and into the air" in South Armagh.

[16] While loyalist attacks on Catholics temporarily declined afterwards and many Protestants became more reluctant to help the UVF, the massacre caused considerable controversy in the republican movement.

South Armagh, however, where the close rural community and family connections of IRA men diminished the risk of infiltration, retained its larger "battalion" structure.

On 17 February 1978 the commander of the 2nd Battalion Royal Green Jackets, Lieutenant Colonel Ian Corden-Lloyd, was killed and two other soldiers injured when the Gazelle helicopter he was travelling in was attacked by an IRA unit near Jonesborough.

The South Armagh Brigade retaliated for the deaths of the hunger strikers by killing five British soldiers with a mine that destroyed their armoured vehicle near Bessbrook.

[29] On 30 December 1990, Sinn Féin member and IRA volunteer,[30] Fergal Caraher, was killed by Royal Marines near a checkpoint in Cullyhanna.

These squads were responsible for killing seven soldiers and two RUC members until the Caraher team was finally caught by the Special Air Service in April 1997.

[32] On 22 April 1993, the South Armagh IRA unit took control of the village of Cullaville near the border with the Republic, for two hours, making good use of dead ground.

[35] The shooting down of the Lynx in 1994 during a mortar attack on Crossmaglen barracks is regarded by Toby Harnden as the most successful IRA operation against a helicopter in the course of the Troubles.

[39] By 1994, the only way for the British army to travel safely across South Armagh and some border areas of Tyrone and Fermanagh was on board troop-carrying Chinook helicopters.

The capture of the sniper team was the single major success for the security forces in South Armagh in more than a decade,[44] and was arguably among the most important of the Troubles,[45] but by then, the IRA and Sinn Féin had achieved huge political gains towards their long-term goals.

Most of the South Armagh IRA stayed within the Provisional movement, but there were reports of the brigade aiding the dissidents in different actions before the signing of the agreement, among them the bombings of Moira and Portadown, and mortar attacks on a security base at Forkhill and a watchtower at Glassdrumman.

[48] The Omagh bombing of August 1998, a botched Real IRA operation which killed 29 civilians, was prepared by dissident republicans in South Armagh.

The normalisation process, negotiated under the provisions of the Good Friday Agreement in exchange for the complete decommissioning of IRA weaponry, was one of the main goals of the republican political strategy in the region.

[54] Senior IRA figures in South Armagh, notably Thomas Murphy, are alleged to have been involved in large-scale smuggling across the Irish border and money-laundering.

[55][56] On 22 June 1998 a deadly incident involving fuel smuggling took place near Crossmaglen, when former Thomas Murphy employee Patrick Belton ran over and killed a British soldier attempting to stop him while driving his oil tanker through a military checkpoint.

[57][58] Some sources claim that the smuggling activities not only made the South Armagh brigade self-sustained, but also provided financial support to most of the IRA operations around Northern Ireland.

[60] A memorial garden was unveiled on 3 October 2010 in the village of Mullaghbawn, near Slieve Gullion mountain, with the names of 24 members of the South Armagh Brigade who died from different causes over the years inscribed upon a marble monument, along a bronze statue of Irish mythological hero Cú Chulainn.

A Police Service of Northern Ireland spokesman confirmed that an investigation was underway, but also stated that both Sinn Féin Ministers and everyone attending the parade were unaware that "the proper paperwork hadn't been submitted".