'Donnerkeil' (i) was the German air cover operation over 'Cerberus' (11/13 February 1942).

In 1941 Kriegsmarine surface vessels had carried out commerce raiding sorties in support of the U-boats in the 'Battle of the Atlantic'. From January 1941 major German warships making raiding sorties into the Atlantic had tried to return to bases in Germany, but British naval superiority meant that three of them, the battle-cruisers Scharnhorst and Gneisenau, and the heavy cruiser Prinz Eugen, could not return to bases in Germany proper or German-occupied Norway, but had instead to put into Brest on the north-western tip of German-occupied France. Here they were subjected to bombing by Air Marshal Sir Richard Peirse’s RAF Bomber Command many times during 1941, the comparatively short distance between British air bases and Brest making it possible for the bombers to fly many missions in rapid order.

Both Adolf Hitler and the Oberkommando der Marine wished that these important warships be moved out of the immediate range of British air attack. In December 1941 the Oberkommando der Luftwaffe received instructions to draft a plan to provide air superiority over the three ships as they escaped from France to Germany through the English Channel in 'Cerberus'. As a result, during January 1942 the General der Jagdflieger, Oberst Adolf Galland, planned 'Donnerkeil' (i) for implementation at the same time as 'Cerberus' on 11 February 1942.

On 12 January 1942 Hitler met the two operational commanders and other senior military leaders at his 'Wolfsschanze' headquarters in East Prussia: those present included Generalfeldmarschall Wilhelm Keitel (head of the Oberkommando der Wehrmacht), General Hans Jeschonnek (chief-of-staff of the Oberkommando der Luftwaffe), General Alfred Jodl (chief of the Oberkommando der Wehrmacht’s general staff), Galland, Grossadmiral Erich Raeder (commander-in-chief of the navy) and Vizeadmiral Otto Ciliax (commander of the squadron of three heavy warships). In this meeting Hitler compared the German fleet with 'a patient with cancer who is doomed unless he submits to an operation. An operation, on the other hand, even though it may have to be drastic, will at least offer some hope that the patient’s life may yet be saved. The passage of our ships is such an operation. It must be attempted.' Little in the way of operational detail was discussed, though the Luftwaffe was ordered to provide both cover over the escaping squadron and diversionary raids against British targets. Jeschonnek promised the commitment of about 250 aircraft.

The Oberkommando der Luftwaffe was not enthusiastic about supporting 'Cerberus', and Jeschonnek remarked to Galland that if 'Cerberus' failed the Luftwaffe would be allocated the greater portion of the blame as, during the meeting of 12 January, the navy had demanded maximum fighter cover and won Hitler’s support, so in the event of a failure, the navy would almost certainly lay on the Luftwaffe the blame for damage caused by British aircraft.

During the meeting Jeschonnek refused to guarantee the safe passage of the squadron, or to reinforce the fighter forces in the western theatre from other theatres.

Galland worked out the details of the plan with Oberst Karl Koller, chief-of-staff of Generalfeldmarschall Hugo Sperrle’s Luftflotte III. To assemble sufficient strength some training units had to be mobilised, for the bulk of Germany’s fighter strength was based in the east for the campaign in the USSR.

The route planned for 'Cerberus' was divided into three sectors based upon the existing Jagdführer (fighter sector) boundaries, but to ensure local control Oberst Max Ibel was appointed as the Jagdfliegerführer Schiff and embarked on Scharnhorst as a signals officer in order to communicate with Luftwaffe units during the operation.

Eight dummy operations, involving around 450 sorties, were made between 22 January and 10 February to train for the mission.

To disrupt British radio transmissions, Generalleutnant Wolfgang Martini’s Funkhorchdienst (radio enlightening, or Sigint, service) attempted to jam the British radio telephone frequencies. The unit also created a subtle jamming technique which increased atmospheric interference and thereby degraded the performance of British coastal radars. In addition Dornier Do 217 twin-engined bombers of Oberstleutnant Georg Pasewaldt’s Kampfgeschwader 2 were ordered to fly electronic deception missions over the western part of the English Channel to divert British aircraft.

General Joachim Coeler’s IX Fliegerkorps of Luftflotte III prepared to attack RAF bases in the south-western part of England and to engage and slow British naval forces that might attempt an interception. Major Gerhard Kopper’s Fernaufklärungsgruppe 123 was responsible for continued reconnaissance over the eastern and western ends of the English Channel, and was also to support the IX Fliegerkorps.

To ensure air support would be provided without intervals, the fighters and night-fighters of the various Jagdgeschwadern and Oberst Wolfgang Falck’s Nachtjagdgeschwader 1 were ordered to ensure very rapid turnround times: aircraft had to be refuelled and rearmed in no more than 30 minutes.

Galland demanded that the air units divided their machines into high- and low-altitude elements in order to provide cover over the full altitude spectrum. Galland also insisted on an umbrella of 16 fighters or more over the ships at any one time along the whole length of the English Channel. Each fighter group was to be divided into two groups of eight aircraft for their respective patrol altitudes, and each group was divided into two Schwärme (flights) of four aircraft. The Schwärme tactics involved one formation flying to sea and one to land in a zig-zag pattern. All Schwärme were ordered to fly up and down the line of ships in wide figure-of-eight patterns and maintain radio silence. Every sortie was meticulously timed to allow the fighters exactly 30 minutes over the ships, enough to maintain cover and allow the relieved units to refuel, rearm and return to start the cycle again. However, during 'Donnerkeil' (i), the relieving sortie would arrive after only 20 minutes, which meant the actual fighter cover over the ships for half the dash would be 32 fighters.

The British plan for implementation if and when the Germans warships made their dash up the English Channel was 'Fuller'. Captain Norman Dening, heading the Admiralty’s Operational Intelligence Centre, was not certain that the Germans would attempt a dash up the English Channel, but regarded it as the stronger possibility than the considerably longer passage right round the British Isles. At the end of January he had warned that the German warships were preparing to put to sea and that a major operation should be expected. Air Marshal Sir Philip Joubert de la Ferté, heading RAF Coastal Command agreed that the English Channel was was the probable route, and expected the Germans to make an attempt anytime after 10 February.

Unfortunately, however, the Air Ministry and the three operational RAF commands (Air Chief Marshal Sir Philip Joubert de la Ferté's RAF Coastal Command, Air Vice Marshal J. E. A. Baldwin’s RAF Bomber Command and Air Marshal Sir Sholto Douglas’s RAF Fighter Command) believed the Germans would make the longest and most dangerous part of their passage in the dark hours, and would therefore depart Brest in daylight. The forces at the RAF’s disposal, far from adequate for the task, would therefore be best reserved for use at night.

Most of RAF Bomber Command was therefore ordered to stand down, and this rendered the command totally unprepared to attack in the daylight hours of 12 February.

RAF Coastal Command had agreed to provide three squadrons of Bristol Beaufort twin-engined torpedo bombers, and the Fleet Air Arm contributed one squadron of Fairey Swordfish single-engined torpedo bombers. RAF Bomber Command had some 300 bombers on standby for any operation. There were many problems, however. The Swordfish biplanes were so slow that their escort by fighters was difficult. The Beaufort squadrons were spread out singly at Leuchars in Scotland, Thorney Island in Hampshire and St Eval in Cornwall, and it was difficult to bring them together.

The Luftwaffe’s force for 'Donnerkeil' (i) comprised Major Erich von Selle’s Jagdgeschwader 1, Oberstleutnant Walter Oesau’s Jagdgeschwader 2 and Major Gerhard Schöpfel’s Jagdgeschwader 26 flying the Messerschmitt Bf 109 (JG 1) and Focke-Wulf Fw 190 (JG 2 and JG 26) single-engined day fighters. The Nachtjagdgeschwader 1 was also pressed into service, but contributed only modest numbers of Messerschmitt Bf 110 twin-engined heavy fighters. The KG 2 flew in the support role, mainly maritime interdiction and air raids on airfields in southern England to distract the RAF from the area of the English Channel.

The confidence of the British bomber force was low. Having received no training in anti-ship warfare, the capability of its crews in this role was poor. The main British hope was therefore placed in the Beaufort and Swordfish torpedo bombers of RAF Coastal Command and the Fleet Air Aarm. The Beaufort machines of Nos 42, 86 and 217 Squadrons were made available by RAF Coastal Command, but were short of torpedoes and were the only Beaufort aircraft available on 12 February 1942 as another 57 aircraft of this type had been diverted to other theatres. Another two units (Nos 415 and 489 Squadrons) had been withdrawn to convert to the Handley Page Hampden twin-engined bomber, and No. 22 Squadron was being transferred to the Middle East at this time. The FAA’s No. 825 Squadron and its Swordfish aircraft were also available, and the Lockheed Hudson twin-engined bombers of the RAF’s Nos 224 and 233 Squadrons were committed for reconnaissance. The RAF’s No. 22 Squadron RAF was recalled from leave to take part in any operation that might eventuate in the English Channel. The Hudson aircraft of the RCAF’s No. 407 Squadron were also available, and were placed on high alert.

RAF Bomber Command contributed Air Vice Marshal R. D. Oxland’s No. 5 Group with 242 out of 300 serviceable aircraft available. Sholto Douglas’s RAF Fighter Command committed Nos 1, 11, 19, 41, 64, 65, 72, 91, 118, 128, 129, 137, 234, 401, 403, 607, 316, 411, 452 and 485 Squadrons.

During the evening of the 10 February the German naval squadron completed its final preparations for 'Cerberus'. As the ships got under way, RAF bombers appeared overhead, and the ships quickly returned to their moorings. The RAF bombers released their bombs but did little damage and, unfortunately for the British, noticed nothing untoward in Brest.

'Ultra' decrypts of intercepted German radio traffic had put the British on alert, but a number of British mistakes and bad luck enabled the German ships to evade early detection. Three Coastal Command Hudson aircraft were patrolling at three different positions. The first was a 'Stopper' patrol which maintained surveillance between sunset and dawn off Brest; the second was a 'Line SE' patrol which watched due north of the port; and the third was a 'Habo' patrol which covered the area between Le Havre and Boulogne. The patrols lasted between 01.00 and dawn on 11 February. At 19.25 on 10 February the 'Stopper' Hudson took off as usual but was intercepted by a Bf 110 night-fighter of NJG 1. The Hudson evaded the Bf 110, but its ASV equipment was unserviceable and the aeroplane headed back to St Eval, landing at 20.40. Its replacement headed over the same area, reaching the location at 22.38. It was too late, for during the interval Ciliax and his ships had slipped their moorings.

The 'Line SE' Hudson should have picked up the German squadron, but its ASV radar failed at 20.55. At 21.50, with all attempts to effect a repair fruitless, the Hudson returned to base and was not replaced.

All now depended on the 'Habo' Hudson, but again the Germans' luck held. At dawn, mist began to form over the airfield at Thorney Island. The mist was threatening to deny a clear landing run for the Hudson, so it was recalled one hour early, just as the German ships were approaching the 'Habo' patrol area. The II/NJG 1 flew 19 sorties, protecting the ships during the night, and was succeeded by the JG 2 at 08.00. For 11 hours the German squadron steamed from Brest to the north-east along the English Channel toward the Straits of Dover.

By chance, a mechanic at the radar station at Fairlight in East Sussex had just finished repairing the station’s equipment when he picked up 27 echoes at 10.15 on 12 February, at a position off Cap Gris Nez. The information was relayed to Vice Admiral Sir Bertram Ramsay, commanding at Dover, who ordered his air liaison officer to contact Air Vice Marshal T. Leigh-Mallory’s No. 11 Group of Fighter Command to request an armed reconnaissance. Ramsay also warned Air Vice Marshal J. H. S. Tyssen’s No. 16 Group of Coastal Command and the FAA squadron operating out of RAF Manston that there were possible targets were in the English Channel, despite not knowing the exact number or size of the German vessels as a result of the fact that the radar’s performance had been degraded by the jamming of the Ballstöranlage sets of two Heinkel He 111 twin-engined adapted bombers which had been flying off the south coast from their airfield near Paris. The flights ceased at 09.00 when installations along the French coast had taken over.

The detection by Fairlight was a piece of good fortune, for the Germans had assumed that it was out of action. Ten Do 217 bombers of Major Gerhard Klostermann’s III/KG 2 flew missions against Plymouth harbour and airfield, while 15 more bombers flew diversionary sorties to keep RAF fighters clear of the He 111 electronic warfare machines.

Ramsay’s request arrived at RAF Kenley, and two experienced pilots (Group Captain F. V. Beamish and Wing Commander F. Boyd) were despatched to investigate. Flying over the channel in Supermarine Spitfire single-engined fighters, Beamish and Boyd ran into large numbers of Bf 109 fighters protecting a large warship force and dived away at 10.42. Maintaining radio silence, the two pilots were able to communicate their discovery only after they had landed at 11.09, and it was another 16 minutes before Bomber Command was alerted and Ramsay did not know of the situation until 11.30.

Soon after this, at about 12.16, the first naval actions began between escorting Schnellboote and British motor torpedo boats, and the British were now fully alerted.

Galland now ordered the end of all low flying and allowed Ibel and his team on board Scharnhorst to break radio silence. Ibel then began to vector Bf 109 and Fw 190 fighters toward RAF units heading to the area. As the first outnumbered British squadrons entered the airspace over the ships, the German vessels were now at the point closest to German airfields, and this made it possible for the Luftwaffe to offer maximum protection.

Lieutenant Commander Eugene Esmonde, leading the FAA’s No. 825 Squadron, led his Swordfish formation into the air at 12.25. Nos 64 and 411 Squadrons were to escort the FAA unit, but arrived over Manston 15 minutes late and missed the rendezvous. The only unit to adhere to its mission orders was Squadron Leader Brian Kingcome’s No. 72 Squadron which, unaware of the Swordfish squadron’s location, met it by accident. As a result of low cloud cover, the British aircraft dropped to between 50 and 100 ft (15 and 30 m). The strength of the German fighter made it impossible for the Spitfire fighters, now themselves hard pressed to survive, to protect the Swordfish machines. The Spitfire and Swordfish aircraft were engaged by the Fw 190 fighters of the 8. and 9./JG 26 led by the Gruppenkommandeur, Major Gerhard Schöpfel of the III/JG 26. The Fw 190 fighters were just relieving fighters of the JG 2. Frail and slow, the Swordfish aircraft forced German pilots to lower their fighters' landing gear to avoid overshooting the biplanes. In the event all six Swordfish torpedo bombers were shot down, while the Spitfires destroyed three Fw 190s. Several Swordfish aircraft managed to drop their torpedoes, but none of these found its mark. Only five of the Swordfish aircraft’s 18 crew survived.

No. 41 Squadron claimed three Bf 109 fighters (most likely of the JG 1) destroyed and one damaged off the Belgian coast. No. 72 Squadron claimed three Fw 190 fighters destroyed and four damaged in the battles at about 13.00. No. 410 Squadron claimed two Bf 109 fighters destroyed and two damaged in the same dogfights.

During this period the German ships needed to use little of their anti-aircraft ammunition as most of the action was fought by the Luftwaffe.

The earlier stand-down order had meant RAF Bomber Command’s contribution arrived only late in the day. The command despatched 73 bombers at between 13.55 and 14.50, and none of these hit its target. At 14.35 nine Beaufort torpedo-bombers of No. 42 Squadron took off and, arriving over Manston at 14.50, found other aircraft of the RCAF’s No. 407 Squadron circling the airfield. It required nearly 30 minutes for the aircraft to form into a proper formation. With several other squadrons they attacked Gneisenau and Prinz Eugen at heights of between 60 and 100 ft (18 and 30 m), but all their torpedoes missed. No. 42 Squadron suffered no losses. The Hudsons struck at between 400 and 900 ft (120 and 275 m), and two of the Canadian bombers were lost as the squadron failed to gain any success. No. 217 Squadron nearly achieved a hit on Gneisenau, but the ship turned away and the salvo just missed. Another wave of between 134 and 137 bombers intercepted the ships between 16.00 and 17.05. Only 20 crews managed to make attacks as a result of inadequate training, a low cloud base of 2,300 ft (700 m) and sea-level visibility of only some 1,000 to 2,000 yards (915 to 1830 m). Nine bombers were lost. Another formation of 35 Vickers Wellington bombers attacked between 17.50 and 18.15, losing two of their number.

The most notable raid in this action was by six Beaufort torpedo-bombers of No. 86 Squadron, three of No. 217 Squadron and three of No. 22 Squadron under the command of Wing Commander C. Flood of No. 86 Squadron as his was the only aeroplane fitted with ASV radar. Locating the German ships in the darkness, the torpedo-bombers attacked, but heavy anti-aircraft fire scattered the aircraft, which scored no hits.

Thus, out of the 242 bombers which took part in the missions, it seems probable that a mere 39 actually attacked, though it is possible that a further 16 carried out attacks, suggesting a total of 54 aircraft actually released their bombs against the ships. Of this total, 15 were shot down.

Fighter Command also committed fighter-bombers in an effort to inflict damage, operating Hawker Hurricane single-engined machines over the Dover area.

The only success the British managed to achieve was to damage both Gneisenau and Scharnhorst, the later seriously. Scharnhorst hit two mines, one at 14.31 and the other at 21.34. Gneisenau also struck a mine at 18.55. Both ships recovered and steamed on. Scharnhorst had been stopped dead in the water with engine damage after the first hit, and the British failure to issue a timely alert to Bomber Command meant the loss of a major chance to attack the battle-cruiser when she was most vulnerable. The second and third mine hits came after the fall of night, which enabled both vessels to avoid further attacks.

The last RAF sighting of the ships had occurred at 18.00. In protecting the bombers, Fighter Command lost 20 fighters, with 14 pilots killed and three rescued and taken prisoner. Only eight of the RAF fighters were shot down by the Luftwaffe. A further eight were shot down by the ships' anti-aircraft fire, two collided, and two were lost to unknown causes. Ten of the fighters were Spitfires, six were Hurricanes and four were Westland Whirlwind twin-engined machines. During the air battles, each side overclaimed, though the Luftwaffe was significantly worse in this respect. RAF Fighter Command claimed 16 Bf 109s destroyed and 13 damaged, as well as four Focke-Wulf Fw 190 single-engined fighters claimed destroyed and six damaged. The actual German losses amounted to 17 fighters, along with five Do 217s, and 23 men killed. German fighter units claimed 60 RAF aircraft shot down, with the JG 26 awarded seven kills and six probable victories. Actual British losses were 41, a number of which were lost to anti-aircraft fire.

The Luftwaffe flew 300 fighter and 40 bomber sorties during 11/12 February. The German squadron reached home ports on the evening of the 12 February.