84 (Sussex) Medium Regiment RA (TA) was converted from 58 (Sussex) Field Regiment RA (TA) in December 1943. It went to France in June 1944 as part of 5 Army Group RA. The Regiment went into suspended animation in April 1946. 84 (Sussex) Medium Regiment RA (TA) was reconstituted as 258 (Sussex) Heavy Anti-Aircraft Regiment RA (TA) in January 1947.
Illustrations of the formation badges under which a unit served or supported are given. This is no guarantee that the unit used this formations badge.
| Dec 43 | Formed from 58 Field Regiment | Felixstowe, Suffolk, UK | |
| Dec 43 |  |
30 Corps | UK |
| Apr 44 |  |
2 Army | UK |
| Jun 44 | |
30 Corps, 5 Army Group RA | Bayeux, France |
| Aug 44 | |
30 Corps, 5 Army Group RA | Falaise Pocket, France |
| Sep 44 |  |
Guards Armoured Division | Brussels |
| Sep 44 | |
Guards Armoured Division | Nijmegen, Holland |
| Oct 44 | |
2 Army, 59 Army Group RA | Groesbeek, Holland |
| Dec 44 | US 84 Division | Brunssum, Holland | |
| Dec 44 | |
Guards Armoured Division | Tilburg, Holland |
| Feb 45 | |
30 Corps, 5 Army Group RA | Eindhoven, Holland |
| Mar 45 | |
30 Corps, 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 |