The IRA (Irish terrorists, for Americans confused at the acronym, or maybe confused at what the IRA did) did occasionally phone warnings and occasionally the information was accurate. Code words were used to authenticate the threat.
The IRA (Irish terrorists, for Americans confused at the acronym, or maybe confused at what the IRA did) did occasionally phone warnings and occasionally the information was accurate. Code words were used to authenticate the threat.
The PIRA actually do seem to have intended to give accurate warnings when they planted bombs, in Belfast at least. There were inevitably cases when the information was garbled or misunderstood but the use of codewords & the practice of delivering the warnings to a known set of media outlets was at least an attempt to minimise these.
The downside was that the vast majority of warnings were hoaxes - bomb scares were dozens of times more common than actual bombs.
The other main groups - INLA, UVF, and UFF/UDA also got in on the hoax game, but didn't often do real bombs (and didn't always give proper warnings when they did - see the UVF's Dublin & Monaghan bombings for a particularly grim example).
But real bombs were just common enough that the hoaxes from whatever source had to be taken seriously and so they caused huge amounts of disruption, probably more than anything that actually exploded.