- the department of state responsible for the British Army, now part of the Ministry of Defence
- the premises of this department in Whitehall, London
Examples from the Web for war office
General Knox was appointed their secretary of the war-office.
I broke the envelope at once, which bore the war-office seal, and as I did so, a perfect avalanche of letters fell at my feet.Charles O'Malley, The Irish Dragoon, Volume 2 (of 2)
Shouldn't be surprised if it were the War-Office Authorities themselves!
Cobden would have done the business of the War-Office in a highly creditable manner.
He cannot remain, as he holds a very important appointment at the War-Office, and his presence is required in London.Soyer's Culinary Campaign