There were three main numerical series of Records created by the Ministry (1922-1924) and the Department (1924-) of Defence, with a more subject-based series following on from these.
The earliest series of files are the Departmental "A-" series, which cover, subject-wise, before, during, and after the formation of the Irish Free State, including the Civil War and its immediate aftermath.
The "2-" series are mostly from the official formation of the Department of Defence in 1924 and continue throughout WWII.
The "3-" series are from the post-war period and some remain active to modern times.
The later subject-based series, which includes files that are being accrued at present, cover from the 1940s until the late 20th century.
