On the night of 11 December 1956, in an operation involving up to 150 Volunteers, the IRA attacked targets in all of the Six Counties.
Attacks on RUC barracks continued in 1957 and early 1958, but were mainly concentrated on the border area. Harsh repression with Internment on both sides of the border, the lack of a co-ordinated, revolutionary political strategy and other factors gradually began to take their toll and the pace on IRA activity.The frequency of successful attacks slowed down by the end of 1958.
The campaign was called off three years later when all Volunteers were ordered to dump arms. Eleven IRA Volunteers were killed in action during the campaign. (Link here-IRA attacks Operation Harvest 1956-62 )
From IRA Internment and the Irish Government Subversives and the State 1939-62. John Maguire.