Entry books and registers of the Secretary-at-War and the Secretary of State for War and also a few kept by independent or subordinate departments, including the Board of General Officers, the departments of the Commissary General of Musters and of the Chaplain General, and the Medical Department (including the Army Nursing Service). Dates given are approximate.

Subjects covered include: commissions and other appointments, records of service and other service matters; embarkation, disembarkation, casualty and deserter information; pay, pensions, absences and discharges; establishments; and the Militia, Army Reserve, defence of Ireland and School of Military Engineering.

The series includes material which would otherwise be found amongst another War Office (WO) division: the Records of the Board of General Officers and records relating to soldiers' clothing.

WO 25 is also available as part of the Digital Microfilm project.