The Chairman opened the discussion by saying that the enemy operation in the Straits of Dover on 12th February 1942 was supported by intentional jamming of R.D.F. Stations.
Minutes of Air Ministry meeting, 23 February 1942
The February 1942 withdrawal of Scharnhorst, Gneisenau and Prinz Eugen from Brest to home waters (Unternehmen Cerberus or—to the British—“The Channel Dash”) was supported by a combined programme of earthbound and airborne jamming which formed part of the overall signals plan, Labyrinth. Setting out the necessary preconditions for the operation, a Navy document of 3 January includes the following:
While passing through the area endangered by radar, everything must be done to jam the enemy to the greatest extent. possible … The Chief of the Naval Signals Service has promised have around 10 jamming transmitters installed on the Channel coast by mid-February. With these the enemy’s land-based sea-targeting radars should be jammed during the breakthrough of the Straits. Furthermore, the flag ship should receive a jamming transmitter so that it can jam any hostile surface shadower.
The Luftwaffe’s radar-jamming service should operate simultaneously with the Navy’s.
On 1 February Luftflotte 3 recorded that:
Jamming of enemy Air Force and Naval radars is prepared for the night before ‘A-Day’ in the Brighton–Lyme Bay sector.
Deployment according to the situation in special agreement with Marine Gruppenkommando West.
For the period a ½-hour before first light on ‘A-Day’ until the onset of darkness in the Isle of Wight–Clacton sector.
On the 5th Marine-Gruppenkommando West had advised Luftflotte 3 of its belief that the ships could pass undetected during the hours of darkness and that to begin fighter escort and RDF jamming at daybreak would just alert the British: “it has been astablished beyond dispute that every activiation of jamming devices is immediately be recognised by the enemy”. Unless the ships were spotted sooner, jamming should commence abruptly when the formation was off Fécamp. Therefore the Navy requested that the Luftwaffe jamming organisation around Cherbourg should come into action if the British were already known to have been alerted, otherwise it start operate only when the jammers covering the Dover Straits came on. After discussing all this, it was agreed next day that jamming in the Straits would go ahead as the Navy suggested. The airmen would however direct what happened at Cherbourg in view of IX. Fliegerkorps’ planned diversionary raids against the English mainland on the first morning. A letter of 4 February from the Chief of Staff at MGr.Kdo. West had spelled out the arrangements:
Jamming of English Air Force and Naval locating devices
1.) Luftflotte 3 has prepared for the jamming of English Air Force sets:
a.) for the sector Brighton – Lyme Bay.
b.) for the sector Isle of Wight – Clacton on Sea.
2.) Mar. Gruppe West is to prepare for the jamming of English sea-targeting sets with the emphasis on the western part of the Straits.
3.) The jamming operation will take place according to the situation, in agreement with Luftflotte 3.
The Navy added two days later that the jamming of radars in the Cherbourg area on “A-Day” would be directed by Lfl. 3 since its bombers would be attacking the English mainland at the time.
Cerberus appears to have been the first time the Luftwaffe attempted jamming from aircraft and the Kriegsmarine Operations Staff diary (as translated postwar) says that:
The bombers of the IX. [Fliegerkorps] accomplished the following:
One plane sent out deceptive radio traffic.
15 planes staged feint attacks in the area northwest of Brest in order to tie down enemy fighters In the area of southwestern England.
10 planes attacked airfields and harbours.
continued on next page …
PART ONE OF TWO
"Radiolocation", 1941 British Army recruiting poster. (National Army Museum)