84 (Sussex) Medium Regiment RA(TA) was converted from 58 (Sussex) Field Regiment RA(TA) in December 1943. The Regiment went into suspended animation in April 1946 and was reconstituted as 258 (Sussex) Heavy Anti-Aircraft Regiment RA(TA) in January 1947.
| Dec 43 | Formed from 58 Field Regiment | Felixstowe, Suffolk, UK |
| Dec 43 | 30 Corps | UK |
| Apr 44 | 2 Army | UK |
| Jun 44 | 5 Army Group RA | Bayeux, France |
| Aug 44 | 5 Army Group RA | Falaise Pocket, France |
| Sep 44 | Guards Armoured Division | Brussels |
| Sep 44 | Guards Armoured Division | Nijmegen, Holland |
| Oct 44 | 59 Army Group RA | Groesbeek, Holland |
| Dec 44 | US 84 Division | Brunssum, Holland |
| Dec 44 | Guards Armoured Division | Tilburg, Holland |
| Feb 45 | 5 Army Group RA | Eindhoven, Holland |
| Mar 45 | 5 Army Group RA | Rhine crossing, Germany |
| May 45 | 51 Infantry Division | Bremervorde, Germany |
Batteries
| Dec 43 | 250, 251 |
Equipment
| Jan 44 | 16 x 5.5 inch Guns |
| Mar 44 | AEC Matador gun tractors |
| Sep 44 | 2 x Sherman Observation Post tanks |
