R ~ Research Centre (Ministry of Munitions)

R & F ~ Rank & File

RA ~ Royal Artillery

RAA ~ Royal Australian Artillery

RAAAIF ~ Royal Australian Artillery Australian Imperial Force

RAAMC ~ Royal Australian Army Medical Corps

RAC ~ Royal Automobile Club

RACD ~ Royal Army Clothing Depot

RAChD ~ Royal Army Chaplains' Department (Royal prefix awarded February 1919)

RACF ~ Royal Army Clothing Factory

RAE ~ Royal Australian Engineers

RAEAIF ~ Royal Australian Engineers Australian Imperial Force

RAF ~ Royal Air Force

RAFA ~ Royal Australian Field Artillery

RAGA ~ Royal Australian Garrison Artillery

RAMC ~ Royal Army Medical Corps

RAN ~ Royal Australian Navy

RANBT ~ Royal Australian Navy Bridging Train

RAOC ~ Royal Army Ordnance Corps

RAP ~ Regimental Aid Post

RAPC ~ Royal Army Pay Corps

RAPD ~ Royal Army Pay Department

RAR ~ Royal Arsenal Railway

RARE ~ Royal Angelsey Royal Engineers

RAS ~ Royal Agricultural Society

RASC ~ Royal Army Service Corps (Royal prefix awarded November 1918)

RATA ~ Royal Army Temperance Association

RAVC ~ Royal Army Veterinary Corps

RB ~ Rifle Bomber

RB ~ Rifle Brigade

RBAAAIF ~ Reserve Brigade Australian Army Australian Imperial Force

RC ~ Railway Commission

RC Coy RE ~ Road Construction Company Royal Engineers

RCC ~ Railway & Canal Commission

RCD ~ Royal Canadian Dragoons

RCD ~ Royal Carriage Department

RCE ~ Railway Construction Engineer

RCF ~ Royal Carriage Factory

RCGA ~ Royal Canadian Garrison Artillery

RCHA ~ Royal Canadian Horse Artillery

RCM ~ Regimental Court Martial

RCO ~ Railway Control Officer

RCR ~ Royal Canadian Regiment

RDB ~ Research Development Formula (munitions)

RDC ~ Railway Defence Corps

RDC ~ Royal Defence Corps

RDF ~ Royal Dublin Fusiliers

RDG ~ Royal Dragoon Guards

RDO ~ Railhead Disbursing Officer

RE ~ Royal Engineers

REC ~ Railway Executive Committee

REPS ~ Royal Engineers Postal Section

RESO ~ Royal Engineers Stores Officer

RESR ~ Royal Engineers Special Reserve

RETC ~ Royal Engineers Train Crew

RF ~ Royal Factory (Ministry of Munitions)

RF ~ Representative Fraction

RF ~ Rim Fire

RF ~ Royal Fusiliers

RFA ~ Royal Field Artillery

RFA ~ Royal Fleet Auxiliary

RFC ~ Royal Flying Corps

Rfcts ~ Reinforcements

RFG ~ Rifle Fine Grain (munitions)

Rfn ~ Rifleman

Rfm ~ Rifleman

RFP ~ Refilling Point

RFR ~ Royal Fleet Reserve

RGA ~ Royal Garrison Artillery

RGF ~ Royal Gun Factory

RGLI ~ Royal Guernsey Light Infantry

RGS ~ Royal Geographical Society

Rgt ~ Regiment

RH ~ Railhead

RHA ~ Royal Horse Artillery

RHA ~ Reserve Heavy Artillery

RHG ~ Royal Horse Guards

RHSD ~ Railhead Supply Detachment

RHTD ~ Reserve Horse Transport Depot

RMTD ~ Reserve Mechanical Transport Depot

RIA ~ Royal Indian Artillery

RIC ~ Royal Irish Constabulary

RIF ~ Royal Inniskilling Fusiliers

RIF ~ Royal Irish Fusiliers

RIM ~ Royal Indian Marine

RIR ~ Royal Irish Regiment

RIR ~ Royal Irish Rifles

RL ~ Regions Liberees (post-war)

RL ~ Royal Laboratory

RLO,HD ~ Returned Letter Office, Home Depot

RLS ~ Returned Letter Section

RLS ~ Registered Letter Section

RM ~ Riding Master

RM ~ Royal Marines

RM 1 ~ Director of Army Contracts - Wool, Woollen & Worsted Goods

RM 2 ~ Director of Army Contracts - Leather & Leather Goods

RM 3 ~ Director of Army Contracts - Cotton, Flax, Jute & Hemp Goods

RMA ~ Royal Marine Artillery

RMB ~ Railway Material Branch

RMB ~ Royal Marine Band

RMD ~ Railway Materials Department

RME ~ Royal Marine Engineers

RMF ~ Royal Munster Fusiliers

RMJ ~ Royal Militia of Jersey

RML ~ Railway Materials Licences

RMLC ~ Royal Marines Labour Corps

RMLD ~ Railway Materials Licences Department

RMLI ~ Royal Marine Light Infantry

RMO ~ Regimental Medical Officer

RMRE ~ Royal Monmouth Royal Engineers

RMSD ~ Railway Material Supply Department

RMSM ~ Royal Marine Submarine Miners

RMSP ~ Royal Mail Steam Packet Co Ltd

RN ~ Royal Navy

RNAS ~ Royal Naval Aircraft Section

RNAS ~ Royal Naval Air Service

RNASBR ~ Royal Naval Auxiliary Sick Berth Reserve

RNCVR ~ Royal Navy Canadian Volunteer Reserve

RND ~ Royal Naval Division

RNMWS ~ Royal Navy Mine Watching Service

RNPS ~ Royal Naval Patrol Service

RNR ~ Royal Naval Reserve

RNR ~ Royal Newfoundland Regiment

RNVR ~ Royal Naval Volunteer Reserve

RO ~ Routine Order

RO ~ Recruiting Officer

RO ~ Roads Officer

RO ~ Requisitioning Officer

ROD ~ Railway Operating Division

RODT ~ Requisitioning Officer Divisional Troops

ROF ~ Royal Ordnance Factories

ROFF ~ Royal Ordnance Filling Factories

ROO ~ Railway Ordnance Officer

RP ~ Regimental Pioneer

RP ~ Regimental Police

RP ~ Rules of Procedure

RP ~ Refilling Point

RP ~ Reply Paid

RP ~ Reserve Park

RPM ~ Revolutions per Minute

RQMS ~ Regimental Quartermaster-Sergeant

RR ~ Roughrider

RRC ~ Member of the Royal Red Cross

RS ~ Regulating Station

RS ~ Ranging Section (Royal Engineers)

RSAF ~ Royal Small Arms Factory

RSF ~ Royal Scots Fusiliers

RSM ~ Regimental Sergeant-Major

RSO ~ Railway Supply Officer

RSS ~ Ranging & Survey Section (Royal Engineers)

RT ~ Range Taker

RTC ~ Reserve Training Centre

RTD ~ Railways Transportation Department

RTE ~ Railway Transport Establishment

RTE ~ Railway Training Establishment

RTO ~ Railway Transport Officer

RTO ~ Railway Traffic Officer

RTU ~ Returned to Unit

RV ~ Receipt Voucher

RVP ~ Reserve Vehicle Park

RVS ~ Remounts & Veterinary Services

RWF ~ Royal Welch Fusliers

RWF ~ Royal Welsh Fusiliers

RWK ~ Royal West Kent Regiment (Queen's Own)

RWR ~ Royal Warwickshire Regiment

RYS ~ Royal Yacht Squadron

Ry TO ~ Railway Transport Officer