Intruder history

German air doctrine had seen little need for the development of an nocturnal night air defence system and the Luftwaffe concentrated on the offensive use of air power.^[8] The failure of the Luftwaffe in the Battle of Britain in 1940 ended hopes for an early conclusion of the war. Faced with German domination of the continent, the only weapon the British could use to exert immediate military pressure on Germany was the night bombing operations of RAF Bomber Command.^[9] Bomber Command had been forced to operate at night since December 1939 and the Battle of the Heligoland Bight when debilitating losses in daylight forced the RAF to abandon these operations. These raids, though inaccurate and wholly ineffective, were causing embarrassment to the Commander-in-Chief of the Luftwaffe and the second most powerful man in Germany, Reichsmarschall (Imperial Marshal) Hermann Göring, who had once boasted "You may call me Meyer" if enemy bombers ever flew over Germany. He ordered the creation a new force set up on 26 June 1940, to combat the night raids.^[10][11][12]

Göring appointed a respected and experienced pilot, Geschwaderkommodore (Wing Commander) Wolfgang Falck to develop a new organisation and consequently Falck founded Nachtjagdgeschwader 1 (Night Fighter Wing 1 or NJG 1). Within a year four more Geschwader (Wings) were founded; Nachtjagdgeschwader 2 (NJG 2), Nachtjagdgeschwader 3 (NJG 3), and Nachtjagdgeschwader 4 (NJG 4). All of these units were in existence by April 1941.^[13] To improve the management of the expanding night fighter force, the Erste Nachtjagd Division (1st Night Fighter Division) was established on 17 July 1940, commanded by Oberst (Colonel) Josef Kammhuber. An aggressive commander, Kammhuber founded the Fernnachtjagd, or long-range night fighter intruder force. The nucleus of this force was derived from I./NJG 2 which would remain the only intruder unit.^[14][15]

The Germans quickly developed a series of basic tactics for intercepting enemy intruders. The lack of airborne radar at this stage in the war meant finding and destroying Allied bombers at night was a difficult prospect, thus it was decided to use the Fernnachtjagd in operations over Britain.^[16] Major Kuhlmann, head of the wireless telegraphy interception service played a significant part in assisting the Luftwaffe night fighter force as did Wolfgang Martini's Luftnachrichtentruppe (Air Signal Corps). Intercepting British signal communications by monitoring the radio traffic of enemy ground stations and aircraft the Germans could determine where and at what airfields RAF night activity was occurring. With the British base identified Falck could then move against them over their own airfields. Three waves could then be deployed; one to attack the bombers as they took off, one to cover the known routes taken by the enemy over the North Sea, and the third to attack them on landing at a time when, after a long flight, enemy crews were tired and much less alert. For operational purposes, Eastern England was divided into four regions or Räume (areas). Raum A was Yorkshire, bounded by Hull, Leeds, Lancaster and Newcastle. Raum B covered the Midlands and Lincolnshire whilst Raum C encompassed East Anglia bounded by London Peterborough, Luton and The Wash. Operations began in earnest in October 1940.^[17][18]

While sound in theory, it proved much more difficult in practice. Inexperience told and by December 1940 NJG 2 had lost 32 aircrew killed in action and 12 aircraft lost in exchange for 18 RAF aircraft claimed shot down. Despite the claims made by German crews, evidence showed a considerable amount of over claiming, and the difficulty in substantiating claims at night and over enemy territory became evident.^[19]

In 1941, the German night fighter intruders began achieving substantial successes. British ground defences, which had taken their toll on the German units in 1940, were now side-stepped by a decision to shift the area of operations to the North Sea, by the English coast. In June German night fighter units claimed 22 RAF aircraft; 18 over the sea. In July 19 British aircraft were claimed for four losses. By October 1941 British loss records listed 54 aircraft of all types destroyed and a further 44 damaged in these operations to all causes. German losses amounted to 27 destroyed and 31 damaged to all causes.^[20]

While the number of losses incurred against German night fighters was not significantly large the psychological damage was substantial. A high number of crashes owed much to nervous British bomber pilots who did not feel safe over their own airfields and consequently landed too hard and fast, or refused to go around a second time for fear of enemy intruders. Just as it appeared that night intruder sorties were showing promise. Adolf Hitler ordered a cessation of operations. For propaganda purposes, he thought that the morale of the German people would be better served by seeing British bombers destroyed and wrecked over German territory. Hitler was also reticent owing the fact there had been no noticeable reduction in British air raids and the RAF had not adopted these methods during The Blitz. This order came into effect on 12 October 1941.^[21][22][23] Kammhuber would unsuccessfully lobby to have intruder operations reinstated and his efforts to expand the intruder force beyond a single unit were thwarted by an uninterested High Command^[15] which was inundated with requests for reinforcements in other theatres.^[24]

Operational situation (1945)

Over the next three years the Combined Bomber Offensive had forced the Luftwaffe to invest heavily in air defence. In the campaign against the RAF, the German air defence system, named the Kammhuber Line, had become increasingly sophisticated. In 1942 the introduction of Lichtenstein radar, despite its early teething difficulties, and greater improvements in the armament and capability of German night fighters produced a force capable of inflicting heavy losses on British bomber streams.^[25] Though British losses rarely reached more than ten percent of a raid—considered a minimum target to irreparably damage British combat power—the night fighter force grew in size and potency.^[26] British losses in the Battle of the Ruhr (March–July 1943) and most notably in the Battle of Berlin (November 1943 – March 1944) reached an all-time high; 569 bombers in the latter campaign.^[27][28]

To increase the toll on Allied bombers further, intruder operations restarted briefly in August 1943 and took place intermittently or on the initiative of single crews, since no organised Fernnachtjagd existed after October 1941.^[29] Success was still possible. On 22 April 1944 the United States Army Air Force (USAAF) 1st Bombardment Division and 3rd Bombardment Division were returning to England in darkening skies after a daylight raid over Germany. They were attacked by an element of Messerschmitt Me 410 bomber destroyers of Kampfgeschwader 51 (KG 51—Bomber Wing 51) over their bases. Over the next twenty minutes, 10 aircraft, nine of them B-24 Liberators, were shot down and 61 men killed for the loss of only two Me 410s and four airmen.^[30][31] The attack coincided with Operation Steinbock, a bombing and intruder offensive against Greater London and in response to the British offensive against German industrial cities, but the operation was aimed at the British capital rather than British bomber bases.^[32]

In mid-1944 a series of developments impaired the German night fighter defence permanently. The most serious was the collapse of the German front around Normandy in August. The defeat led to the advance of the Allied armies across France into Belgium and the southern Netherlands. The Kammhuber Line which ran through these countries was eliminated, leaving only the northern portions, in northern Germany, the Netherlands and Denmark intact and exposing the Ruhr.^[33] Night fighting over France and Europe was also proving increasingly costly. The RAF consistently struck on moonlit nights and bombers were accompanied by a strong number of long-range de Havilland Mosquito night fighter intruder escorts from No. 100 Group RAF.^[34] As a consequence of these developments, and just three months after the German night fighter arm's most successful campaign over Berlin, it was fast becoming an insignificant force.^[35] Although numerically stronger and with more formidable aircraft designs than ever before (including the Heinkel He 219), the British were winning the electronics war and had succeeded in jamming German radar and radio communications to the extent German countermeasures were "useless".^[35] German SN-2 radar and Naxos radar detector had been negated by new Bomber Command tactics.^[36] These tactics resulted from the capture of the sets by the British in July 1944 which allowed the RAF to develop counter-measures.^[37]

The oil campaign over Romania and against the synthetic oil plants in the Ruhr—in which most oilfields had been destroyed, captured or damaged by 1945—triggered a critical fuel shortage from the autumn of 1944 onwards which denied the Luftwaffe the resources to capitalise on its numerical strength. Paradoxically, production was able to replace the relatively small losses and operational serviceability reached an all-time high since ground crews had more opportunity to work on machines. The Luftwaffe was still capable of taking a toll on Bomber Command on occasion, but unless more powerful radars and communications could be introduced in time it was doubtful British air superiority at night could be challenged.^[38] The impotence of the night fighter force as an organisation was demonstrated during the attack on Dresden when the second wave of Allied bombers was hardly opposed. Operation Clarion, launched later that month, was not adequately opposed either.^[39]

Intelligence breach

Unfortunately for the Germans security was breached within weeks. On 1 January 1945, after participating in Operation Bodenplatte to support the German Ardennes Offensive, a Ju 88 (code D5+PT) flown by Unteroffizier (Corporal) Lattoch belonging to 9./NJG 3 landed at Luxembourg in error. Lattoch had been present at the briefing on 1 December 1944 and was taken prisoner of war. He was soon handed over to the intelligence branch of the US Ninth Air Force. He divulged the details of the meeting and this information was passed to the Air Ministry.^[46]

RAF Fighter Command and Bomber Command attempted to warn all of their airborne units of the potential danger and bomber units were ordered to plan alternate landing sites in the event of an attack on their airfields. All bomber and fighter groups were linked by telephone and ground control passed on all details of intruder operations to pilots including height and heading when they occurred. Station Commands organised blackouts of airfields and pilots could be ordered to switch the navigation lights off at any time. Only the Mosquito groups remained active against intruders, though the majority of these units were supporting Allied operations on the continent.^[46]

The British propaganda radio station Soldatensender Calais (Soldiers' Radio Calais) was used to conspicuously broadcast to the Germans that they knew about a planned intruder operation. The station did so by playing the contemporary song I dance with Gisela tonight. The operation was suspended repeatedly until the British relaxed vigilance.^[47][48]

The British raid

At midday on 3 March 1945 teletype messages from Bomber Command Headquarters at RAF High Wycombe began reaching the airfields of RAF squadrons in Eastern England. On this night a planned raid with moderate numbers of bombers was planned over western Germany. A complex plan of feint attacks and diversions to deceive German air defence system were drawn up. The main force was split into two separate groups in the Münster area; No. 4 Group RAF were ordered to destroy the synthetic oil plant at Kamen and No. 5 Group RAF would attempt to eliminate the aqueduct, safety gates, and canal boats on the Dortmund–Ems Canal at Ladbergen.^[49]

Nearly 5,000 RAF airmen prepared to take part in 817 heavy bombers which were fuelled and armed in the evening. A trigger plan was prepared, which would act as a feint but, this night, Bomber Command amended the feint which was partially compromised by weather conditions. Restrictions on the flight path of the bombers was also changed. Bomber streams were permitted to fly over Ingoldmells Point to Filey; but not over coastal areas where no ground defences were stationed. The route took them downstream to southern England by Reading, and across the English Channel, as the trigger plan required. However, they were then ordered to turn back toward the North Sea. The reason behind this was the low-lying cloud which was ever-present over the continent that night. The clouds made it difficult for pilots to see and steer clear of zones heavily guarded by Allied ground defences near to the frontline. The possibility of losing aircraft to friendly fire was too great.^[49]

At 18:00 the first aircraft began to take-off. The first RAF aircraft over Germany were medium bomber variants of the de Havilland Mosquito. No. 8 Group RAF committed 89 to bomb Berlin and Würzburg. The Mosquitos marked the area with target indicators while 64 others dropped 59 tons of bombs. Six Mosquitos marked Würzburg which was then while 24 others each dropped a Blockbuster bomb in a concentrated area east of the river causing a large fire. None of the crews noticed any defence of the target.^[49][50]

No. 5 Group RAF and No. 1 Group RAF committed 15 and 16 Avro Lancaster bombers to drop naval mines in Oslo harbour. Around 36 Mark IV and 54 Mark VI mines. One No. 1 Group Lancaster was shot down by a NJG 3 Ju 88 night fighter patrolling the Kattegat near Denmark; Major Werner Husemann achieved his 33rd air victory in this action which was confirmed through British records. No 1 Group claimed a victory against a Ju 88 in return. No. 11 Group sent 12 Handley Page Halifax bombers and four Short Stirlings which formed a Mandrel Screen to jam long-range Freya and Würzburg radar. They patrolled in orbit for 120 minutes over the North Sea. Meanwhile one Mosquito and seven Halifaxes from No. 192 Squadron RAF accompanied No. 4 Group to Kammen while monitoring enemy radio transmissions.^[49]

Other diversion operations included 40 Lancasters, 19 Halifaxes and 35 Vickers Wellingtons from No. 7 Group RAF flying toward the Frisian Islands. Some aircraft withdrew owing to mechanical difficulties but 91 dropped 3,721 bundles of Window over the North Sea. Five Halifaxes, three B-24 Liberators and eight B-17 Flying Fortress also assisted with jamming operations. The USAAF committed 24 B-24s to bomb Emden in support of the main force. In the final pre-amble to the main attack No. 100 Group committed 10 Halifaxes and six Mosquitos to drop target markers over Meppen to mislead German ground controllers into believing it was the target. The bombers struck Ladbergen, and the canal burst its banks, the safety gates were overwhelmed and canal boats were stranded. The attack lasted just 25 minutes.^[49]

The jamming operations were effective, but the decision to pack a large number of aircraft into relatively small airspace made it certain that German night fighters would locate some aircraft. At this time, German policy was to commit only Experten to battle as they had the skill and experience to find and shoot down Allied bombers. The first fighters were being vectored onto their targets as the bombs began to fall on Ladbergen. Four pilots claimed all eight of the Lancasters lost on the raid out of an operating force of some 203 bombers. Geschwaderkommodore of NJG 4, Heinz-Wolfgang Schnaufer claimed two; Hauptmann (Captain) Hermann Greiner claimed three; Hauptmann Josef Kraft claimed two, while Major Martin Drewes claimed one.^{[49][51][52][53]}

No. 4 Group attacked Kamen. Mosquitos from No. 8 Group marked the target from 28,000–35,000 feet (8,534–10,668 m). No 8 Group also sent 21 Lancasters to assist. They dropped 98 tons of high explosive which effectively illuminated the synthetic oil plant for the following 181 Halifaxes. Although German night fighters were seen, none attacked the bombers. A total of 690 tons of bombs hit the target area in 10 minutes. The 29 Mosquito night fighters sent by RAF Fighter Command orbited the area in the hope of intercepting any German fighters. Two German night fighters were claimed destroyed and one damaged for no losses.^[49] German sources confirm two night fighters destroyed over Germany to enemy aircraft and four damaged.^[54]

Gisela: German counter-attack

Wolfgang Martini's Luftnachrichtentruppe (Air Signal Corps) had already busied themselves with searching the air waves for signs of a British raid. Before the first RAF bombers had taken off, they had already determined that a raid of at least 500 aircraft would take place that night. The Luftwaffe defences were alerted. Shortly afterwards the code word Gisela was issued to fighter units. Some German units did not treat the message with the urgency required. It is likely, after several months, unit officers did not remember the significance of the name and it took time for the crews to recall that it signified the offensive air patrol they were briefed about in late 1944. Crews were given a re-fresher briefing to compensate for the three-month time-gap. They were informed there was a wind blowing northerly at 50 kilometres per hour (31 mph). A strong front was moving across the North Sea which meant the bombers would fly above it on the return leg. The fighters would have to fly under it, in heavy rain to keep below British radar defences.^[55]

The first Ju 88s took off at 23:00 and began heading toward the Dutch coast where they dived to sea level and stayed at approximately 50 metres while they flew out to sea. Crews were forbidden to engage enemy aircraft over the North Sea in order to preserve surprise until the last possible moment. The rain and squall assisted crews in judging the location and distance of the water. However, with crews prone to human error, it was decided to use the very accurate FuG 101 radar altimeter and the Ju 88s blind-flying instruments. The strain on the crews was enormous, as a careful vigil was kept on them until the British coast was reached and the pilot began his ascent to the height of the returning bomber stream. As they did so, the Ju 88s released Düppel to obscure the radar of Mosquito fighters. The pilots were then free to begin their attacks.^[56][57]

Just after midnight on 4 March 1945, as the bombers crossed over the English coast, a Ju 88 night fighter opened fire on a No. 214 Squadron RAF B-17, returning from a Window patrol. The bomber was damaged but evaded its attacker, landing safely at RAF Oulton. The combat was the opening salvo of Gisela. The station commander at Oulton reported an intruder over his station and soon after radar screens picked up large numbers of hostile aircraft. The headquarters of 100 Group were alerted and a scramble order given to Mosquito squadrons. A "scram" order was also issued to bomber units still airborne; it signified a warning to number crews that intruders were in the vicinity and they were to divert to airfields in western or southern England, and out of danger. The second victim of the night was a Mosquito of No. 169 Squadron RAF which was probably shot down while en route to its alternative landing site.^[56]

A large number of bombers only began receiving their warning and diversion orders at 00:45 hours. Halifaxes of No. 4 Group were finally alerted at this time. It was too late to prevent the Ju 88s from sighting, and then homing in on a mass of landing lights. Crews from NJG 2 and NJG 4 were able to deliver beam and Schräge Musik attacks against the unwary crews. Pilots that were alerted in time were able to carry out a corkscrew manoeuvre, and evade the attack. Some bombers were able to land but were then subjected to strafing attacks and destroyed though the crews were presented with a greater chance to escape.^[58]

At RAF Winthorpe the Ju 88s attacked bombers illuminated by the landing lights. Leutnant Arnold Döring of IV./NJG 3 engaged and destroyed two bombers between 01:05 and 01:15 using his Schräge Musik. The British crews that witnessed the action switched off their navigation lights and he did not engage another bomber successfully. Döring had been told not to return with any ammunition so he engaged any targets of opportunity. He shot up a locomotive and set a wagon on fire. During the ten-minute time-frame Döring had claimed his victories, nine bombers had been destroyed. At 01:05 60 of No. 5 Group's Lancasters were still airborne and further losses were incurred against NJG 5 machines.^[59]

No. 100 Group were searching for intruders in force by 01:30, at which time the intruders had already spent 90 minutes over England. Several Ju 88s were chased out to sea and two were claimed as shot down. Three Ju 88s crashed while making ground attacks on targets of opportunity. Leo Zimmermann of NJG 5 attempted to attack an Air Transport Command B-24 using his Schräge Musik but was spotted. Evasive action by the pilot avoided an attack and the Ju 88 was seen to crash into the ground after its wing tip made contact with the runway. Eight minutes later Heinrich Conze, also of NJG 5, attempted to attack a car driven by Royal Observer Corps member Mr J P Kelway. The Ju 88 struck power lines as it attacked and crashed into the car killing Kelway and the German crew. Over Pocklington Johann Dreher and his crew attempted to attack a landing Halifax and then a taxi that had its headlights on and was travelling along a parallel road near the airfield. Dreher hit some trees as he dived to low-level and all aboard were killed. The crews had the distinction of being the last German airmen to crash on British soil during the war.^{[60][61][62][63]}

The most dangerous part of the operation was over by 02:15. The intruders had spent over an hour in British airspace. Now the journey back over the sea to Germany and the Netherlands was undertaken. The British had jammed German radio beacons and switched on others with the same frequency. It was hoped the move would fool German pilots into landing in Britain in error. Experienced pilots did not fall for the ruse. Still, they had to fly over the sea by dead reckoning.^[64][65] A consequence of this showed that while around only five Ju 88s were lost in combat over England, eight crews were missing, three were killed in crash-landings and had died from their injuries, six crews had baled out 11 aircraft crashed or were damaged on landing.^[2]

German claims

Below is likely only an incomplete record of claims submitted by German crews during Gisela. It is certain that some of the crews that did not return from the operation also would have filed claims for air victories.^[66][67][68]

British losses

British records list the loss of 15 Handley Page Halifax and 12 Avro Lancaster four-engine bombers which made up the vast majority of casualties. Two Mosquitos were lost, one of which presumably fell in combat. Nine aircraft were listed as damaged.^[5][69]
  Airframe damaged
  Airframe severely damaged
  Airframe destroyed

German losses

At the time of Gisela, the Ju 88 was the only fighter available in the necessary numbers, with the required range, to reach eastern England and return. As a consequence, all German losses were Ju 88s. Below is a list of German losses during the operation.^[3][4][61]
  Airframe damaged
  Airframe severely damaged
  Airframe destroyed