I of A ~ Instructor of Artillery

I of M ~ Regimental Instructor of Musketry

i/c ~ in charge of

IA ~ Indian Army

IAA ~ Indian Army Act

IACC ~ Indian Army Corps of Clerks

IAF ~ Independent Air Force

IAF ~ Indian Army Form

IAF ~ Independent Force Royal Air Force

IAMC ~ Indian Army Medical Corps

IAMC ~ Inter Allied Munitions Council

IAMCCH ~ Inter-Allied Military Control of Hungary

IAO ~ Indian Army Order

IAOC ~ Indian Army Ordnance Corps

IAPSS ~ Indian Army Printing & Stationery Services

IARO ~ Indian Army Reserve of Officers

IAS ~ Indian Army Staff

IAVC ~ Indian Army Veterinary Corps

IBC ~ Indian Bearer Corps

IBD ~ Infantry Base Depot

IBDAIF ~ Infantry Base Depot Australian Imperial Force

IC ~ Internal Combustion (mechanical transport)

ICCAIF ~ Imperial Camel Corps Australian Imperial Force

ICCB ~ Imperial Camel Corps Brigade

ICD ~ Indian Cavalry Division

ICE ~ Internal Combustion Engine

ID ~ Investigation Department

IE ~ Illegal Enlistment

IE ~ Inspector of High Explosives

IEAMS ~ Imperial East African Medical Service

IEF ~ Indian expeditionary Force

IEF ~ Italian Expeditionary Force

IF, RAF ~ Independent Force, Royal Air Force

IG ~ Irish Guards

IGC ~ Inspector-General Communications

IGT ~ Inspector-General Transportation

IHFE ~ Inspector of Horse Feeding & Economies

IHL ~ Imprisonment with Hard Labour

ILC ~ Indian Labour Corps

ILH ~ Imperial Light Horse (South Africa)

ILS ~ Inspector of Laboratory Stores

IMA ~ Inspector Munitions Area

IMD ~ Indian Medical Department

IML ~ Indian Miscellaneous List

IMS ~ Inspector of Medical Services

IMT ~ Indian Marine Transport

IMT ~ Inspector of Mechanical Transport

IMT ~ Inspectorate of Mechanical Transport

Inf ~ Infantry

Inspr.S&T ~ Inspector of Supplies & Transport

INV ~ Irish (National) Volunteers

IO ~ Intelligence Officer

IOC ~ Instructions for Officers Commanding

IOD ~ Indian Ordnance Department

IOM ~ Inspector of Ordnance Machinery

IOO ~ Inspector of Ordnance Officers

IOR ~ Indian Other Rank

IP ~ Inspector of Propellants

IPS ~ Indian Postal Service

IQMGS ~ Inspector of Quartermaster-General's Service

IQMGS, HF&E ~ Inspector of Quartermaster-General's Service, Horse Feeding & Economies

IQMGS, M&E ~ Inspector of Quartermaster-General's Service, Messing & Economies

IRCS ~ Imperial Rest Camp Staff (India)

IRES ~ Inspector of Royal Engineers Stores

IRO ~ Infantry Regimental Officer

IRS (AT) ~ Inspector of Rolling Stock (Ambulance Trains)

IS ~ Inspector of Searchlights

IS ~ Inland Section

IS.CPS ~ Imperial Staff Corps (India)

ISC.CPS ~ Imperial Service Camel Corps (India)

ISMD ~ Indian Subordinate Medical Department

ISO ~ Imperial Service Obligation

ISO ~ Companion of the Imperial Service Order

ISTC ~ Indian Service Transport Commissariat

ITC ~ Interallied Transportation Council

ITO ~ Infantry Transport Officer

IUL ~ Indian Unattached List

IV ~ Issue Voucher

IW ~ Issue Warrant

IW&D ~ Inland Waterways & Docks

IWGC ~ Imperial War Graves Commission

IWT ~ Inspector of War Trophies

IWT ~ Indian Water Transport

IWT ~ Inland Water Transport

IWTRE ~ Inland Water Transport Royal Engineers (West Africa)