War Department

'War Department' (WD) is used in this encyclopedia for locomotives built or requisitioned for British military service in the First and Second World Wars and operated by the War Department, the Railway Operating Division of the Royal Engineers, or by overseas military authorities to British account.

The First World War saw mass orders of ROD 2-8-0s (a development of the Robinson GCR 8K) for service in France, Egypt and Mesopotamia. The Second World War saw Riddles's WD Austerity 2-8-0 (935 built) and 2-10-0 (150 built) for service across Europe, the Middle East and (post-war) into the early 1990s on Greek and Hong Kong railways.

British WD locomotives were built by various contractors, typically North British Locomotive Company, Vulcan Foundry, Beyer Peacock and the LNER's Doncaster Works, and operated under WD numbers and an austere unlined black livery.