On the morning of 17 May 1974, four cars are stolen in Belfast. That evening, they would explode without warning in Dublin and Monaghan resulting in the deaths of 34 civilians and injuries to more than 300. The bombings were the worst single atrocity in Ireland during the “Troubles.”

The bombings were a Loyalist reaction to the Sunningdale Agreement and attempts to introduce power sharing between Loyalist and Nationalists in Northern Ireland.

The first of the three Dublin bombs went off at approximately 5.28pm without warning, at Parnell Street, near the intersection with Marlborough Street. The second bomb went off at about 5.30 on Talbot Street, near the intersection with Lower Gardiner Street. The third bomb went off at about 5.32 on South Leinster Street, near the railings of Trinity College and not far from Leinster House. The streets all ran east-west from busy thoroughfares to railway stations. There was a bus strike in Dublin at the time, which meant there were more people on the streets than usual. According to one of the Irish Army’s top bomb disposal officers, Commandant Patrick Trears, the bombs were constructed so well that 100% of each bomb exploded upon detonation.

The scene was one of carnage with dead, dying and thought to be dead brought to make shift mortuaries. Fifteen year old Derek Byrne regained consciousness at the morgue where he had been pronounced dead. “I was just lying on the table. It was full of bodies. I just let out a scream. The mortuary attendant then let out a scream.”

News of car bombs in Dublin and Monaghan raised tensions in Northern Ireland. Sammy Smyth, press officer of both the Ulster Defence Association (UDA) and the Ulster Workers’ Council (UWC) Strike Committee, said, “I am very happy about the bombings in Dublin. There is a war with the Free State and now we are laughing at them.”

The Irish Press reported:

“Seconds after the blasts, as the pall of smoke rose from the streets, dazed survivors saw the normal home-going rush of people turned into a scene of carnage. There were bodies, some limbless, some blasted beyond recognition, some burned, lying on the pavements. Scores of others badly injured and many knocked out by the blast or shocked by the impact were hurled into windows and side streets. For some time it was impossible to distinguish between the dead and the injured.”

The relatively lightly injured Liam Sullivan told the official Barron Report into the bombings what he saw at the hospital “I will never be able to explain what I saw over there. It was like a slaughterhouse. There were bodies everywhere and people being operated on.”

Almost ninety minutes later, at about 6:58, a fourth bomb exploded in the centre of Monaghan town. It had been parked outside Greacen’s pub on North Road. The car had been stolen from a Portadown car park several hours before. As in Dublin, no warning had been given. This bomb killed five people outright, and another two died in the following weeks. There is evidence that the car bomb was parked five minutes before the explosion. The bomb site, which was about 300–400 yards (270–370 m) from the Garda station, was preserved by a roster of eight Gardaí from 7:00 on 17 May until 2:30 on 19 May, at which time the technical examination of the area had been completed. Forensic analysis of the metal fragments taken from the site suggested that the bomb had been in a beer barrel or similar container. It has been suggested that the Monaghan bombing was a “supporting attack”; a diversion to draw security away from the border and thus help the Dublin bombers return to the north.

The UVF only admitted responsibility for the attacks in 1993, but did not give any motive for them. Nobody has ever been charged with the bombings and there have been widespread allegations of collusion between loyalist paramilitaries and British security and intelligence services.

The Barron Report quotes the then Secretary of State for Northern Ireland Mr. Merlyn Rees, in relation to a subversive faction in British Army Intelligence: ‘It was a unit, a section out of control. There is no doubt it reflected the views of a number of soldiers.’ “Let’s go in and fix this lot”, and so on. But that it went on, and that it went on from Lisburn, and it went on from the Army Information Service and those associated with it, I have no doubt at all.’

The Garda Síochana and Irish Government has also been criticised about events following the bombing. Some early strong evidence related to the bombers was not pursued. Also, evidence disappeared including a car registration plate with a fingerprint of one of the suspected bombers.

Barron reported: “The Garda investigation failed to make full use of the information it obtained. Certain lines of inquiry that could have been pursued further in this jurisdiction were not pursued”

The Irish Government’s efforts finding the killers was criticised as lack-luster and uninterested. This may have been a deliberate decision due to the incredibly high tensions of the time. Had the involvement of British security forces become public knowledge, it would have caused an absolute firestorm of emotion and almost certainly even further violence.