They provide details of IRA operations and activities across more than 8,000 locations, including names of those who took part in them. Most of the activities date from April 1920 to July 1921, when the War of Independence was at its height, but there are also a small number of files holding information about earlier and later activities in which the Irish Volunteers and IRA were involved.
The reports include drawn maps and sketches – a total of 402 of them cover the locations of IRA operations in all four provinces – interactive Google maps for exploring operations, fatalities and executions by geographical areas, a gallery of photos (mostly memorial cards), and timelines. There is also a well-produced 171-page Guide (26Mb), downloadable from the BAR home page, which includes context to the collection and several essays by established Irish historians exploring specific themes or locations. This seems to me the best place to start after an initial rummage!
Researchers should note in the introduction to this record set that the files are not a definitive listing of IRA operations during the Independence struggle, and a number of companies and units do not appear in the Activity File series. There are also inconsistencies in terms of the activities and events covered, and the information provided by different brigades and units.