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DAC: Divisional Ammunition Column.
DADMS: Deputy Assistant Director of Medical Services.
DADOS: Deputy Assistant Director of Ordnance Services.
Danton Class: Six French Pre-Dreadnought vessels.
Daffadar: Indian sergeant of cavalry.
DAG: Deputy Adjutant-General.
Daisy Cutter: Shell designed to explode upon impact with the ground, scattering shrapnel through the air.
DAMS: Defensively Armed Merchant Ships.
DAN: Détachement d’Armée du nord.
DAQMG: Deputy Adjutant and Quartermaster General.
Dardanelles Operation: An attempt made in February and March 1915 by the British and French navy to force a passage through the heavily defended Dardanelles Straits. It came surprisingly close to succeeding, although this wasn't known at the time.
Daylight Gun: American nickname for the Benét-Mercié machine gun, derived from a joke that it couldn’t be loaded in the dark!
DCLI: Duke of Cornwall's Light Infantry.
DCM: Distinguished Conduct Medal.
DDMS: Deputy Director of Medical Services.
DDVS: Deputy Director of Veterinary Services.
Defence in Depth: A strategy of trench warfare whereby defences were built many layers deep, allowing defenders to withdraw to prepared positions during an initial bombardment and attack and then bring their weapons to bear on pre-targeted areas during a counter. It differed from the initial, but gradually abandoned, tactic of defending a single line against everything.
Deflector Gear: Special plates fitted to an airplane’s propeller to deflect bullets from a machine gun. It allowed guns to be fired straight forward, improving accuracy, without damaging the blades. The technology was soon replaced by Interrupter Gear.
De Havilland DH Series: See Airco DH Series.
Dekko: To have a look, still in contemporary use.
Demonstration: As well as the usual meaning, a feint attack, whether with troops or artillery.
Depth Charge: A specially made waterproof bomb which only detonated at a certain depth, used to attack submarines.
Derby Scheme: British system of recruitment.
Derfflinger Class: German Battlecruisers.
Desecar: Serbian corporal of the 2nd and 3rd Ban.
Desetar: Montenegrin corporal.
Deserter: Someone who leaves their military unit without permission.
Destroyers: Relatively small, speedy ships deployed as a screen to protect fleets from the threat of torpedo craft, to scout and to deflect the attacks of other fleets.
Devil Dogs: German nickname for American marines.
DFPS: Détachement François de Palestine and Syria.
DFW: German aircraft maker.
DFW C-Types: A series of two seater armed German biplanes.
DGMS: Director General of Medical Services.
DI: Division d'infanterie, Infantry Division.
Difua: Divisions-Funkerabteilung, German divisional wireless detachment.
Digger: ANZAC soldier.
Dilution: The acceptance of untrained workers into specialist, previously closed, jobs.
Dinkum: Australian colloquialism for 'good'; also a veteran of Gallipoli.
Dinkum Oil: Proven news.
Director Control: The standard method of co-ordinating fire from Battleships involving one Director taking readings and feeding these to the individual guns, instead of the guns each taking their own readings.
Dis: Shortened version of disconnected, to lose communication.
Ditch: A tank becoming grounded because the ground was so soft/waterlogged the tracks couldn't find traction.
Divkonach: German divisional signals commander.
Division: Army unit of two-three brigades and support.
Dixie: British army kettle.
DKK: Divisions-Kraftwagen-Kolonne, German mechanised transport column.
DLOY: Duke of Lancaster's Own Yeomanry.
DMAP: Dépot Matérial Automobile et Personnel, French central motor transport depot.
DMC: Desert Mounted Corps.
DMI: Director of Military Intelligence.
DMO: Director of Military Operations.
DMS: Director of Medical Servies.
DMT: Director of Motor Transport.
DNI: Director of Naval Intelligence.
'Do An Alley': To go off.
Dogfight: Colloquial term for aerial battles.
Don R: Dispatch Rider.
Doolally / Doolally Tat: Mad/insane.
DORA: Defence of the Realm Act, a piece of British legislation in 1914 granting the government special wartime powers.
Dorsal Gun: A machine gun fitted on some airplanes.
Doughboys: Popular nickname, also used officially, for US troops.
Dover Barrage: An Allied attempt to block the English Channel using mines and indicator nets.
DOW: Died of Wounds.
DQMG: Deputy Quartermaster General.
DR: Division d'infanterie de Réserve, French reserve infantry division.
Draft: A reinforcement sent to currently existing units.
Dreadnought: Both a revolutionary British battleship finished in 1906 which rendered all previous craft obsolete and the class of heavily armed, armoured and powerfully driven ships which followed as other nations caught up.
Dreckfesser : 'Mud Eater', German nickname for infantry.
Drift: The tendency of a shell to shift to the right because of rifled barrels.
DRT: Director of Railway Transport.
Drum Fire: A barrage created by a unit of guns firing in succession, not all at once.
DSA: Direction des Services Automobile, French motor transport.
DSO: Distinguished Service Order.
DST: Director of Supplies and Transport.
D-Stoff: Phosgene Gas.
DU: Dauernd-untaugliche, unfit for service.
Dual Alliance: Both the 1879 Austro-German Alliance and the 1894 Franco-Russian Alliance.
Dual Monarchy: Austria-Hungary.
Duck-Board: Wooden planking used at the bottom of trenches or across muddy ground; also slang for the British Military Medal.
Duck-Board Patrol: A night time patrol through unmanned sections.
Dud: Either a shell which failed to explode or anything poor/of little use.
Duff: Either pudding or ‘to do something badly’.
Dug-Out: Usually a shelter in a trench, named because they had been 'dug out', varying from a small hole to a large underground room, but also a retired soldier brought back to duty against their wishes.
Dum-Dum: A bullet which splinters/spreads on impact causing worse than normal damage.
Dunsterforce: A force of roughly one thousand elites troops from the British Empire commanded by General Dunsterville deployed briefly in the Ottoman Empire.