This series covers correspondence relating to the Australian Imperial  Forces, dealing with such matters as appointments, strengths, embarkation, discharges, enlistments, stores, rations, equipment, training and communications. Registered correspondence was given a Department of Defence stamp bearing an AIF imprint. Files were apparently kept in grey Department of Defence jackets, but many papers without related correspondence, and some files, were transferred to Archives without jackets and have been placed in folders. The series contains unclassified, confidential, and secret correspondence. The numbering system was based on that used for the 1913-1917
correspondence series (A2023) but as this was a more specialized series, some of the primary subject divisions allowed for in that system did not have to be used. It was a three number system with a primary number allocated to major subjects, a secondary number allocated to divisions within the subject and a third number allocated to papers consecutively upon receipt. Each paper received was registered. If it related to previous papers it would be placed with them to make a file and was put away according to the latest number. When looking for an individual paper it is usually essential to refer to the registration booklets (B 540) whichrecords these attachments.
 This series was subject to heavy culling in the late 1920's and again in the early 1950's by the department. The registration booklets (B 540) give some guide to these destructions, stamps having been placed on some entries to the effect that the papers had been destroyed or transferred to Archives. No files, other than those held by the Victorian Branch areknown to be extant.