Series consists of records created and/or maintained by the Department of National Defence (DND), and its predecessor, the Department of Militia and Defence (M&D), and which were managed within the central registry system established in 1903. When DND was created in 1923, it adopted the 1903 central registry system as the record keeping system for the new department and continued to add documents to existing M&D files.
Shortly after 1903, the Chief Registration Clerk created a separate Classified Filing System to manage documents classified as confidential or higher. The file numbers in this system were independent from the 1903 system and were prefixed by HQC, HQS or HQTS, according to their security classification. (See Mikan Record No. 4921903.)
Originally, records of the Department of Naval Service (created in 1910) and of the Air Board (created in 1919) were included in the 1903 HQ system but were removed when separate registries were created for the Navy in 1938 (See RG 24 Series D-1-a) and for the RCAF in 1940 (See RG 24 Series E-1-a).
The 1903 system continued in use for Army records until the outbreak of the Second World War. At that time, the file numbering system was completely overhauled to accomodate the growth in the Canadian Army, with numbers being reassigned and others retired so as to creating more of a block structure. (See RG 24 Series C-1-b.)
Records created and received at Headquarters that related to the overall defence programme and the department, and not specifically the army, continued to be maintained in the 1903 system until its disbandment in 1948. As a result, the records in this series relate to the complete range of defence activities from the late 19th century until the end of the Second World War.