The British Army had been on heightened alert since early December 1989, when intelligence suggested an imminent IRA attack in the County Tyrone area. The warning was accurate. On 13 December 1989, an IRA team riding an improvised armoured truck attacked a permanent vehicle checkpoint at Derryard in County Fermanagh, just a few yards from the border with the Republic. The checkpoint was guarded by soldiers of the King's Own Scottish Borderers. The attackers used machine guns, rocket-propelled grenades, and a flamethrower. Two KOSB soldiers were killed in the assault. British military sources at the time described the IRA approach as 'professional' and 'calculating.' By February 1990, intelligence was focused on IRA personnel based in County Monaghan, just over the border in the Republic, supported by an East Tyrone Brigade unit operating out of Clogher in Northern Ireland.

The Gazelle was flying from the 656 Squadron of the Army Air Corps, conducting a routine patrol along the border country. The crew, four soldiers including the pilot, would have been doing what Gazelles did in this region throughout the late 1980s and early 1990s: observation, courier work, occasional troop lifts, and the low-altitude movement that made small reconnaissance helicopters the eyes of Operation Banner. The Aerospatiale Gazelle is a small, lightly built helicopter with a fenestron tail rotor, designed for liaison and light observation rather than combat survivability. It does not carry armour. Three of the four crew were wounded when the aircraft broke up in the forced landing. By the standards of helicopter losses, the outcome could have been catastrophically worse.

The weapons used remain a matter of speculation. Some sources have suggested Soviet-designed DShK 12.7mm heavy machine guns, part of the substantial Libyan arms shipments that reached the IRA in the 1980s under Muammar Gaddafi. Others have suggested American M60 7.62mm general-purpose machine guns. Either way, the firing came from across the international border in the Republic, where the firing party could melt into the local population before any British response could cross the line, and where any RUC or Garda follow-up faced jurisdictional complications. The ZB687 sighting was one of the first clear demonstrations that the IRA was now equipped to engage helicopters with sustained heavy-calibre fire, not just opportunistic rifle bursts.

The strategic significance of the shootdown showed in the British Army's response over the following two years. By 1992, the use of long-range weapons by the Provisionals, mortars, heavy machine guns, and eventually surface-to-air missiles, had forced the British Army to pull its main permanent checkpoints back one to five miles inside Northern Ireland to put them out of range of fire from across the border. The era of border posts physically on the line, like the one attacked at Derryard, was over. Helicopters became more careful about their flight paths and altitudes. The escalations continued. On 19 July 1991, the crew of a British Army Westland Wessex successfully evaded a surface-to-air missile at Kinawley in Fermanagh. On 15 March 1992, an IRA unit fired more than 1,000 rounds at two helicopters from across the border near Roslea in Fermanagh. On 8 January 1993, a helicopter was hit by heavy machine-gun fire at Kinawley after a mortar attack on a nearby army outpost. On 12 December 1993 near Fivemiletown, automatic rifle fire downed another helicopter after the ambush in which two RUC officers from Clogher barracks were killed.

The crash site was sealed off by the RUC and the British Army. The investigation that followed mapped the trajectories of the rounds that had struck the Gazelle, recovered the airframe, and traced where the firing had come from. By the standards of border-country incidents in 1990, the search ended where it always ended: at the boundary line on the map. The shootdown did not produce a body count. It produced a precedent. Combined with the Derryard attack two months earlier, it told the British military command that the war along the border had entered a phase in which sustained, well-equipped, well-aimed fire from across an international line had become a permanent feature, and that the rules of patrol, of basing, of helicopter operation, would all have to change. Within five years, the ceasefires of 1994 and the steady run-up to the Good Friday Agreement would begin to render the calculation moot. But on 11 February 1990, in an open field between Augher and Derrygorry, the shape of the next phase of the conflict had already been written into the broken fuselage of ZB687.