| O'Brien | J | 2536 | Private | Severely wounded. Bethlehem, 6 July 1900
1st Battalion.
Source: South African Field Force Casualty Roll | Royal Munster Fusiliers |
| O'Brien | J | 6326 | Private | Severely wounded. Kroonstad, 24 September 1901
1st Battalion. Accident
Source: South African Field Force Casualty Roll | Royal Munster Fusiliers |
| O'Brien | J | 3308 | Private | Slightly wounded. Belfast, 8 January 1901
1st Battalion.
Source: South African Field Force Casualty Roll | Royal Irish Regiment |
| O'Brien | J | 1356 | Colour Sergeant | Slightly wounded. Stenekamp, 8 April 1902
1st Battalion.
Source: South African Field Force Casualty Roll | Prince of Wales's Leinster Regiment (Royal Canadia |
| O'Brien | J | 3099 | Private | Slightly wounded. Stinkhoutboom, 24 July 1900
1st Battalion.
Source: South African Field Force Casualty Roll | Royal Dublin Fusiliers |
| O'Brien | J | 1342 | Lance Corporal | Wounded. Belmont, 23 November 1899
1st Battalion.
Source: South African Field Force Casualty Roll | Coldstream Guards |
| O'Brien | J | 2992 | Private | Wounded. Vrede, 7 October 1900
2nd Battalion.
Source: South African Field Force Casualty Roll | Grenadier Guards |
| O'Brien | J | 2853 | Private | Wounded. Zuikerbosch, 21 July 1900
2nd Battalion.
Source: South African Field Force Casualty Roll | Royal Dublin Fusiliers |
| O'Brien | J | 2919 | Private | 1st Malta Company, 9th Battalion Mounted Infantry
Source: QSA roll | Lancashire Fusiliers |
| O'Brien | J | 6862 | Private | 28th Mounted Infantry
Source: QSA roll | Lancashire Fusiliers |
| O'Brien | J | | | 1st Battalion
Source: QSA and KSA medal rolls | King's Royal Rifle Corps |
| O'Brien | J | 2973 | Private | 2nd Battalion
Source: QSA roll | Lancashire Fusiliers |
| O'Brien | J | | | 2nd Battalion
Source: QSA and KSA medal rolls | King's Royal Rifle Corps |
| O'Brien | J | | | 2nd Battalion
Source: QSA and KSA medal rolls | Cheshire Regiment |
| O'Brien | J | | | 4th Battalion
Source: QSA and KSA medal rolls | Cheshire Regiment |
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