This series comprises registered files of the War Office dealing with all aspects of the administration of the departments and the armed forces. They include files opened in the War Office and continued in the Ministry of Supply (SUPP) after 1939; and files pertaining to functions restored to the War Office in 1959.

With the unification of the Ministry of Defence in 1964, the War Office became the Army Department of the Ministry of Defence, its registered files are generally to be found thereafter in DEFE 70, but there is some overlap with this series.