The Regiment was originally raised as a Medium Regiment in 1920, as 51 (Cornwall and Warwickshire) Medium Brigade RA(TA) at St Austell in Cornwall. It converted to Anti-Aircraft in October 1932 as 56 (Cornwall) Anti-Aircraft Brigade RA(TA) at Falmouth in Cornwall. The unit was re-designated as 56 (Cornwall) Anti-Aircraft Regiment RA(TA) in January 1939, becoming Heavy Anti-Aircraft in June 1940. It was re-designated as “B” Medium Regiment RA(TA) in June 1940 and re-designated two weeks later as 56 (Cornwall) Medium Regiment RA(TA) . The Regiment was converted to 86 (Cornwall) Medium Regiment RA(TA) in August 1944. It was placed in suspended animation in May 1946 and reconstituted as 456 (Cornwall) Heavy Anti-Aircraft Regiment RA(TA) in January 1947.
| Sep 39 | 35 Anti-Aircraft Brigade, 5 Anti-Aircraft Division | Plymouth, Devon, UK |
| Sep 40 | 55 Anti-Aircraft Brigade, 8 Anti-Aircraft Division | Plymouth, Devon, UK |
| Mar 42 | Madras Area | India |
| May 42 | 13 Anti-Aircraft Brigade | Bombay/Madras area, India |
| Feb 43 | 3 Indian Anti-Aircraft Brigade | Bombay/Madras area, India |
| Feb 44 | 9 Anti-Aircraft Brigade | Bombay/Madras area, India |
| Mar 44 | 33 Indian Corps | Galunche, India |
| Jul 44 | 9 Anti-Aircraft Brigade | Poona, India |
| Jul 44 | Became 86 Medium Regiment |
Batteries
| Sep 39 | 165, 201, 202, 203 |
| Dec 41 | 165, 201, 202 |
| Mar 43 | 154, 165, 201 |
| Jul 44 | 165, 201 |
