| Unit Name: | No. 515 Squadron RAF |
| Dates: | 1 Oct 1942 – 10 Jun 1945 |
| Country: | United Kingdom |
| Branch: | Royal Air Force |
| Role: | Electronic countermeasures |
| Command Structure: | No. 11 Group RAF, Fighter Command No. 100 Group RAF, Bomber Command |
| Motto: | Latin Cleriter ferite ut hostes nacesit |
| Identification Symbol: | A gauntlet holding a winged dagger in bend sinister, trusting to the dexter |
| Identification Symbol Label: | Squadron Badge heraldry |
| Identification Symbol 2: | 3P (Feb 1944 – Jun 1945) |
| Identification Symbol 2 Label: | Squadron Codes |
No. 515 Squadron RAF was a squadron of the Royal Air Force formed during the Second World War. It ushered in Electronic countermeasures (ECM) warfare, jamming enemy radar installations from October 1942 as the only such squadron in the RAF initially. Later in the war 515 Sqn was joined by other squadrons as part of No. 100 Group RAF. The squadron disbanded after VE day, when the need for such a specialised squadron had reduced.
The squadron was formed from Defiant Flight, also known as Special Duties Flight – an electronic countermeasuress unit equipped with the Boulton Paul Defiant Mk.II – at RAF Northolt on 1 October 1942, It moved to RAF Heston later that month. As part of 11 Group, 515 Sqn performed radar jamming duties, using Moonshine and Mandrel equipment.
From May 1943, 515 Sqn re-equipped with the Bristol Beaufighter Mk.IIF.
The squadron transferred to No. 100 Group RAF in December 1943 as part of Bomber Command, and moved to RAF Little Snoring in Norfolk. There they re-equipped with de Havilland Mosquito Mk.VIs in March 1944, and operated these for the remainder of the war. At the time of its disbandment on 10 June 1945, 515 squadron had carried out 1,366 operational sorties with the Mosquito with a loss of 21 aircraft, with most of its aircrew transferring to No. 627 Squadron RAF. T
Moonshine was the code-name for ARI TR1427, (Airborne Radio Installation Transmitter Receiver), a British airborne spoofer/jammer installed in the 20 modified Boulton Paul Defiants of No. 515 Squadron RAF to defeat Freya radar and was developed at the Telecommunications Research Establishment (TRE).
Mandrel was the code-name for a jammer deployed against Freya and Würzburg radars used by aircraft of 515 sqn and 100 Group. Developed at the TRE, Mandrel was also built in the United States as AN/APT-3.
| October 1942 | December 1943 | Mk.II | ||
| June 1943 | April 1944 | Mk.IIf | ||
| February 1944 | April 1944 | Mk.II | ||
| March 1944 | June 1945 | de Havilland Mosquito | Mk.VI |
| 1 October 1942 | 29 October 1942 | dets. at RAF Coltishall, RAF West Malling, RAF Tangmere and RAF Exeter | |
| 29 October 1942 | 31 May 1943 | RAF Heston, Middlesex | |
| 31 May 1943 | 15 December 1943 | ||
| 15 December 1943 | 10 June 1945 | ||
| October 1942 | July 1943 | S/Ldr. S.R. Thomas, DFC, AFC | |
| July 1943 | January 1944 | W/Cdr. J.F. Inkster | |
| January 1944 | December 1944 | W/Cdr. F.F. Lambert, DSO, DFC | |
| December 1944 | June 1945 | W/Cdr. H.C. Kelsey, DFC |