| | | |
| ILLAWARRA REGIMENT | |
| IMPERIAL BUSHMEN CORPS | |
| IMPERIAL CAMEL BRIGADE | |
| IMPERIAL CAMEL CORPS | |
| IMPERIAL JAPANESE ARMY | |
| IMPERIAL JAPANESE NAVY | |
| IMPERIAL MOUNTED DIVISION | |
| IMPERIAL WAR GRAVES COMMISSION | |
| IMPERIAL WAR MUSEUM | |
| INDEPENDENT COMPANIES | |
| INDEPENDENT FIELD SQUADRONS | |
| INDI LIGHT HORSE | |
| INDIAN ARMY | |
| INDIAN LABOUR CORPS | |
| INDIAN MULE CORPS | |
| INDIAN NAVY | |
| INDONESIAN FORCES | |
| INFANTRY BATTALIONS | |
| INFANTRY BRIGADES | |
| INFANTRY CORPS | |
| INFANTRY DIVISIONS | |
| INFANTRY OFFICERS TRAINING SCHOOL, BONEGILLA | |
| INFANTRY REGIMENTS | |
| INFANTRY TRAINING UNITS | |
| INFANTRY TROOPS WORKSHOPS | |
| INFANTRY UNITS | |
| INITIAL TRAINING SCHOOLS (RAAF) | |
| INITIAL TRAINING SCHOOL, KINGAROY | |
| INITIAL TRAINING SCHOOL, SOMERS | |
| INITIAL TRAINING SCHOOL, VICTOR HARBOUR | |