STRATEGIC BOMBING aims to systematically destroy those resources which will most weaken an enemy by denying them the materials or weapons they need to continue a war. One of the main objectives of the Allies’ Combined Bomber Offensive, launched in the summer of 1943 and carried out during the last two years of the war, was to shut down Germany’s aircraft industry and to cut off the flow of usable aircraft to Hitler’s fighter squadrons. Preventing or disrupting the development of new aircraft or aero engines was never a specific item on the agenda, but it was an inevitable by-product of the intensive onslaught unleashed upon the aircraft and engine plants.
During their time in Germany the Fedden Mission came face to face with several examples of the destructive power of the Allied bombing raids and also the measures taken by the Germans to circumvent their effectiveness. Of the various plants they visited, without exception those which had been known to the Allies had been severely damaged. As Fedden commented in the final report, ‘Several of the places it was hoped to examine were found to be so badly bombed that there was nothing to be seen’. The Junkers works at Dessau, for example, were so extensively damaged that little of value could be found, and it was a similar story at the Jumo engine plant at Magdeburg, used to manufacture and overhaul the Jumo 109-004 jet engines. ‘A number of wrecked jet engines, destroyed in the air raids, were seen lying about,’ observed Fedden. Of the Daimler-Benz Untertürkheim plant in Stuttgart he wrote, ‘These works had been very badly damaged and production had been almost entirely dispersed during 1943-44.’ It was the same at the Bosch works at Stuttgart and with BMW at Stassfurt. Only the most secret sites, such as the LFA research institute at Völkenrode or Messerschmitt’s experimental and design department which transferred to Oberammergau in October 1943, and the carefully concealed or dispersed facilities, such as the Mittelwerk at Nordhausen, that had escaped unscathed. Everywhere else the devastation to industry and the transportation infrastructure was absolute and, as this excerpt from an official US government report on the effects of the strategic bombing campaign testifies, no country could carry on functioning for long under these circumstances:
Wrecked Me 262s amid the rubble of the bombed Messerschmitt factory at Obertraubling in Bavaria. (LoC)
Even a first class military power – rugged and resilient as Germany was – cannot live long under full-scale and free exploitation of air weapons over the heart of its territory. By the beginning of 1945, before the invasion of the homeland itself, Germany was reaching a state of helplessness. Her armament production was falling irretrievably, orderliness in effort was disappearing, and total disruption and disintegration were well along. Her armies were still in the field. But with the impending collapse of the supporting economy, the indications are convincing they would have had to cease fighting – any effective fighting – within a few months. Germany was mortally wounded.
So why was it that the Luftwaffe, equipped with the world’s first operational jet fighter in the Me 262, not to mention rocket-powered interceptors and all manner of guided weaponry, had been unable to hold back the enemy bombers? For the answer to this question we need go back to the beginning of the war when the role of Germany’s newly formed air force had been defined as supportive to the army within Hitler’s doctrine of lightning-fast Blitzkrieg offensives. It was all about quick-fire attack. All evidence suggests that Hitler regarded the war in the west as being over by October 1940. Yes the British were a nuisance, but what harm were they likely to cause? Reichsmarschall Hermann Göring once famously boasted that no enemy bomber would ever reach Germany’s industrial heartland. ‘If one reaches the Ruhr,’ he joked, ‘my name is not Göring. You may call me Meyer’ (a highly derogatory term). And when Hitler’s forces were poised to seize Leningrad and Moscow it must have seemed that the war in the east was about to be successfully concluded too. At that point Germany was not under any direct threat, neither was there any expectation of conducting a prolonged bombing campaign on an enemy’s industrial base and, accordingly, there was no great impetus to step up aircraft production. In this situation the German aircraft industry was meeting the Luftwaffe’s existing production requirements with comparative ease. In fact it was operating with 100 per cent excess capacity as it was customary for aircraft plants to work on only a single daytime shift basis. Neither were women brought in to boost the workforce, as was the case in both Britain and, later, the USA.
But the cracks in this strategy of complacency through strength had already begun to appear by the autumn of 1940. Only a matter of months after Hitler had abandoned Operation Sealion – the intended invasion of Great Britain – the RAF hit back, commencing with a number of daylight raids against Germany’s industrial centres in an effort to weaken the economy and undermine the morale of the German population. Unfortunately for the British airmen their own losses on these missions were extremely high while the tonnage of bombs dropped was quite small, especially when compared with the combined bomber offensive of the final year of the war; only 16,000 tons dropped in 1940 and 46,000 tons in 1941, as opposed to a staggering 676,000 tons in 1944. While the physical damage inflicted in those early raids was not particularly significant perhaps, the appearance of the British aircraft above the Fatherland undermined public confidence and was a source of huge embarrassment for Göring. It wouldn’t be long until the Germans began deriding the regular wailing of the air-raid sirens as the ‘horns of Meyer’.
Me 262 aircraft found by the advancing Allies at a ‘Waldwerk’ or forest factory near Obertraubling. (NARA)
Me 262s under cover: The entrance to the low buildings of the forest factory has been carefully concealed under camouflage netting. (NARA)
The biggest shake-up of the German armaments industry came unexpectedly in February 1942. Following the sudden death of Fritz Todt in an aircraft accident Hitler immediately promoted Albert Speer, the Reich’s chief architect at the time, to take charge of the Reichsministerium für Rüstung und Kriegsproduktion (RfRuK or Reich Ministry for Armament and War Production). This may have been a deliberate pre-emptive ploy to prevent the power-hungry Göring from claiming Todt’s ministerial powers for himself, but Speer was both loyal to the Führer and a very capable organiser. He immediately set about rationalising the nation’s war production, centralising control and achieving a threefold increase in output through the elimination of inefficiencies and improving the utilisation of existing industrial plant and facilities. Then, on 30 May 1942, the RAF made the first of its controversial ‘thousand plane’ raids on German industrial and urban centres, starting with Cologne and followed two nights later by an attack on Essen. This was followed up in the summer of 1943 when the port of Hamburg was singled out for one of the most devastating attacks of the entire war, carried out over three successive days and resulting in the destruction of around one-third of all the houses in the city and the deaths of 60,000 to 100,000 people. The Nazi leaders were shaken to the core, as Speer later confided: ‘I reported for the first time orally to the Führer that if these aerial attacks continue, a rapid end to the war might be the consequence.’
And the odds were already stacking up against the Nazis. Back in 1941, on 7 December, aircraft of the Imperial Japanese Navy had launched their notorious surprise attack on the US naval base at Pearl Harbor, Hawaii. The following day President Roosevelt signed his country’s declaration of war against Japan. In loyalty to their Japanese ally, both Germany and Italy reciprocated by declaring war on the USA on 11 December 1941. It is said that Hitler was furious with the Japanese for dragging the US into the war when he had yet to gain full control of continental Europe, but he still believed that American bombers would never dare to attack Germany. He was wrong.
Under the Combined Bomber Offensive (CBO) the might of the RAF and the USAAF, backed up by the USA’s formidable industrial base, were brought together to strike at the heart of Germany. At its peak this entailed a round-the-clock offensive with the RAF attacking at night and the USAAF by day. As far as targeting the German aircraft industry was concerned, the bombing offensive can be divided into two distinct periods. The first half, starting in April 1943 and through to May 1944, is referred to as the High Priority Campaign and focussed on the aircraft industry and the U-boat bases as the main strategic targets. The second half of the Combined Bomber Offensive, described as the Low Priority Campaign, took place from June 1944 right through to the end of the war in April 1945, and although the aircraft industry was still targeted it was no longer a main priority as a strategic target.
The first phase of the High Priority Campaign, beginning in April 1943 and continuing up to the autumn, saw bombing raids on those plants manufacturing the Messerschmitt Bf 109 and the Focke-Wulf Fw 190 fighter aircraft, plus one attack on an engine plant and several on the ball bearing plants at Schweinfurt. At this stage in the war these locations were at the extreme range that the Allied bombers could reach when still flying with protection from fighter escorts. Official records state that the first phase ended with ‘no discernible results’ in terms of disruption caused, but it did incur heavy losses for the Allies. Accordingly, over the winter of 1943 and into 1944, there was a brief hiatus in the proceedings to allow time for a build-up of heavy bomber strength and to await delivery of America’s new P-51 Mustang long-range fighter which would be able to escort the bomber formations right into the heart of Germany. The P-51D was a formidable aircraft with a maximum range of 1,650 miles (2,755km) when equipped with external fuel tanks, and an impressive maximum speed of 437mph (703km/h) at 25,000ft (7,620m). Performance-wise, they were more than a match for the Messerschmitt Bf 109s and they just had the edge on the Focke-Wulf Fw 190s.
A pair of Jumo 004 engines discovered in one of the forest factories. (USAF)
The CBO resumed in the new year, with deep penetration raids carried out under fighter escort, and from 20 to 25 February 1944 the bombs rained down upon twenty-three of Germany’s airframe plants plus three of the aero-engine works. March to May 1944 saw the heaviest bombing of aircraft targets of the whole campaign. Every single aircraft plant was hit and by late April Germany’s synthetic oil plants were beginning to replace the aircraft factories as strategic targets.
While these heavy attacks left the airframe plants at Marienburg, Augsburg, Wiener Neustadt and Dessau as smoking ruins, the raids were still regarded as failures in strategic terms as they caused only minor disruption to the fighter aircraft output. The Allies had failed to appreciate the tremendous recuperative powers of Germany’s aircraft industry, which was partly due to its inherent spare capacity and the fact that the machine tools were remarkably durable even though the buildings might be in ruins. More often than not it was a case of just clearing the rubble and starting up again.
In response to the onslaught Germany’s Jägerstab (‘fighter staff’) was formed in February 1944 and the responsibility for aircraft production was wrested from the Luftwaffe and placed in the hands of Albert Speer’s Ministry of Armaments and War Production. Speer faced two very different problems: how to increase aircraft production – in particular for the fighter aircraft – while also protecting the plants from further bombing damage. The solution was to be implemented in three stages: firstly, decentralising aircraft production through dispersal; secondly establishing safe facilities underground either in mines or tunnels; and finally instigating an ambitious plan to construct six large and impregnable weapons plants. Dividing the manufacturing process into smaller and less vulnerable units also established multiple supply sources not only for components and parts, but for the sub-assembly and final assembly of aircraft. If one site was hit then another could take on the work.
An American serviceman examines an unfinished Me 262 at an underground assembly plant near Kahla. (NARA)
Dispersing production was the quickest policy to implement. Over the next twelve months twenty-seven of the main airframe plants were split and relocated to around 300 smaller facilities, and the fifty or so engine plants were scattered to more than 200 different locations. The process of dispersal was aided by the ministry but the actual expense remained the responsibility of the individual companies, although they had little choice in the matter. Likewise, the workforce had to do what it was told and had to put up with moving to the new locations. A limited amount of dispersal had already taken place before 1944. The first important aircraft factory to be dispersed had been the Focke-Wulf plant in Bremen. Located in the north-west part of the country this was considered to be especially vulnerable to attack and following RAF raids in 1940 and 1941 its production facilities were divided between several sites at Marienberg, Posen, Cottbus and Sorau, all of which were deeper within Germany to the east and south-east of Berlin.
Messerschmitt’s plants had been heavily hit in the latest round of Allied raids, and the large areas of forest in the Augsburg area offered the obvious means of concealment via dispersal to a number of Waldwerke, or forest factories. In no time there were more than a dozen such factories hidden in the woods and the plant at Horgau, about 7 miles (11km) west of Augsburg, was typical of one of these set ups. Located beside the autobahn, it consisted of twenty-one timber buildings, including barracks for 845 workers, which were painted green and hidden from view beneath a combination of camouflage netting and overhanging foliage. Production work was carried out on a two-shift basis, assembling wing panels, nose and tail sections for the Me 262 which were then transferred to a nearby final assembly plant. The concealment of the forest factories was so successful that none was detected by aerial reconnaissance during the war, although Allied fighters did attack a number of Me 262s half hidden along the motorway. The autobahn served as a makeshift runway to send the aircraft on their way to the operational bases and the Fedden team reported seeing several Me 262s still on the stretch between Stuttgart and Munich, although it should be remembered that the Luftwaffe also made operational use of autobahn runways towards the end.
During the summer of 1944 the Germans had a brief respite from the incessant raids as virtually all Allied air power was concentrated on establishing air superiority in preparation for the D-Day landings at Normandy and the subsequent breakout. Then in September the CBO resumed with jet aircraft production given a priority second only to the oil plants. The list of specific targets included jet airframe and engine factories, conventional aircraft engine factories, fighter airframe factories, any airfields particularly associated with jets, and all airfields with concentrations of fighter aircraft. In most cases each target was attacked on a handful of occasions, although some were subjected to multiple attacks – possibly up to eleven times. This onslaught resulted in considerable damage to the buildings and facilities, but once again the effect on production was minimal as most plants had been dispersed by this time and several of the underground sites were starting to become operational.
The initial movement below ground had commenced as early as 1943 when orders had been given to identify suitable underground locations following the RAF’s Operation Hydra raids on the V-weapon research station at Peenemünde. The damage caused had been immense and for the Germans it demonstrated the vulnerability of such large above-ground facilities. Accordingly production of the V-weapons – both the V-1 flying bombs and the V-2 (A4) rockets – was transferred to an extensive network of tunnels burrowed into the Harz mountains near the village of Nordhausen. (These works were visited by the Fedden Mission to Germany and its findings are described in Chapter 7.) Once the German High Command had given priority to the production of jet fighter aircraft a number of airframe and engine plants were also moved underground. The scale of the underground sites varied enormously depending on whether they were natural caves and quarries or more extensive mine workings which, in certain cases, were massively extended or adapted for their new roles. Usually these sites are referred to by the nearest village (the choice of village appears to vary with different sources of information) and they were also allocated misleading codenames to throw Allied intelligence off the scent. Old mines and tunnels were usually named after various animals or fish, for example, while new tunnel systems were given geological designations.
Production of Junkers aircraft was relocated to a deep salt mine at Tarthun, about 12 miles (19km) to the south-west of Magdeburg. Work began on preparing the site in March 1944 and production had commenced by December that year. In a series of tunnels and galleries occupying an area of about 200,000ft2 (18,580m2), the 2,400 workers worked in shifts on the Heinkel He 162 Volksjäger. One photograph, taken after the site was discovered by the 1st US Army in April 1945, shows a gallery with over thirty He 162 fuselages all neatly lined up in a row. Apparently the moisture-absorbing qualities of the salt resulted in very satisfactory working conditions, although the capacity of the lone elevator cage made access awkward. Junkers occupied further underground facilities near Halberstadt in the Champignon Caves, a system of old quarry workings, codenamed Makrele (‘mackerel’) I and II, for the manufacture of aircraft parts and fuselages for both the He 162 and Ju 88.
The aero engine companies also sought safety underground. Production of the Jumo 109-004 turbojet was moved into the north end of the Nordhausen complex, and to the Malachit (malachite) tunnels under the Takenberg hills, also near Halberstadt and slightly further to the west of the Tarthun mines. This extensive grid of interlocking caves was created by excavating new workings, started in June 1944, connected to an entrance from an existing sandstone quarry. The aim had been to manufacture turbine components for 1,000 engines every month but production only commenced in April 1945. Daimler-Benz moved part of its plant into a 500,000ft2 (45,000m2) gypsum mine near Heidelberg, codename Goldfish, and BMW occupied railway tunnels at Markirch, near Strasbourg.
With hindsight, it would have been far more effective if the Allies had gone for the aero-engine manufacturing plants or the foundries that produced specialist castings for the jet engines from the outset and before they went underground. Albert Speer himself commented on this point after the war:
We were surprised for a long time that you attacked the airframe production and not the motor production. There were only a few big factories … If you had attacked the motor factories at first and not the airframe, we would have been finished.
Dispersing and hiding the production facilities obviously provided protection from the bombs, but it also concealed them from prying eyes, as this official US government report later confirmed:
After the industry dispersed, however, the quality of our intelligence deteriorated. We not only did not know the locations of many important units in the dispersal pattern, but we seriously underestimated the production capabilities and recuperability of the German industry.
Dispersal did cause its own problems, however, as Fedden noted:
We were told of organisations which had been dispersed to four different sites in fourteen months. It would be common for a firm to have hardly been settled down in a new place, before they had to be moved to another.
The dispersal had other effects including a dilution of technical talent, an increase in the need for indirect workers engaged in transportation and handling, and it placed a far greater reliance on the transportation system, in particular the railways. Furthermore, as the bombing offensive continued and the disruption increased the aircraft companies faced delays in the supply and delivery of essential materials, in particular aluminium, magnesium and high-strength steel alloys. For airframe construction this was mitigated to some extent by the simplification of designs and the greater use of more readily available materials such as steel or wood. As for the turbojets, the requirement for nickel and cobalt was minimised as much as possible and new methods of heat-proofing were developed including aluminium coatings to protect steel fan blades against oxidisation.
He 162 Volkjäger fuselages being assembled at Junkers’ underground facility at Tarthun. (NARA)
Inevitably the headlong rush to meet production targets and the problems caused by the new working situations resulted in issues concerning the quality of workmanship. The cracks were starting to show, literally. On an aircraft such as the Me 262 a smooth finish is important to minimise drag, but increasingly the gaps between badly fitting panels were being smoothed over with a filler paste. Fedden reported:
A shortage of raw materials and difficulties from our bombing attacks made many changes necessary. The chief engineer of BMW said that during the war he had had to change the steel of his poppet valves ten times, and his crankshafts three times, necessitating check tests in every case.
But time and time again the clear message was that it was the destruction and disruption of the transport infrastructure that had the greatest effect on productivity and effectiveness:
Several of the firms said that the bombing of their communications was more serious than the bombing of the factories as, with few exceptions, the factories could be got going again comparatively quickly. The bombing of communications however was fatal, and cut down, for instance, piston engine production, from the spring of 1943 to the spring of 1945, to one third of what it had been previously.
When the Allies shifted their focus to attack the transport infrastructure, in particular the railways, bridges and marshalling yards, and also the oil and synthetic fuel plants, the problems of moving components, materials or completed aircraft were further compounded. Monthly production figures for synthetic fuels fell from 316,000 tons to 17,000 tons by September 1944, and output of aviation fuel fell from 17,500 tons to a meagre 5,000 tons. In the spring of 1944 Germany’s consumption of oil was already exceeding production and by the end of the year virtually all of the reserves had been used up. For the beleaguered Luftwaffe the run-in time for new aircraft engines was cut from two hours to ninety minutes, and all pilot training was drastically reduced to save precious fuel. Synthetic rubber production also suffered from the attacks on the oil industry.
IMPREGNABLE WEAPONS PLANTS
In the end the dispersal measures proved self-defeating. The ultimate way to circumvent some of the production and infrastructure difficulties was to centralise production centres, either in huge bunkers or underground, where every aspect of an aircraft’s production could be carried out at a single well-protected site. In 1944 work began on a series of semi-subterranean bomb-proof bunkers in the Landsberg area, near Kaufering in Bavaria, specifically for the large-scale manufacture of the Me 262. These new facilities were part of a project named Ringeltaube (‘wood pigeon’), instigated by Albert Speer’s ministry. Three cavernous arched bunkers, each 1,300ft (400m) long and 278ft (85m) wide, were to be constructed starting with the first, codenamed ‘Weingut II’ (‘vineyard II’).
It was built by heaping up tons of excavated gravel to create a former or mould for the vast semi-cylindrical concrete roof which consisted of 8in (20cm) of light cement interlaced with iron rods, capped with a further covering of heavy concrete. This was considered adequate to resist even the RAF’s 6-ton bombs. Once the concrete had set the gravel was then removed and used in the construction of the other parts of the structure. Weingut II was so vast that the plans included an underground runway for the departure of the finished Me 262s, although assistance from liquid-fuelled rocket-assisted take off (RATO) units would probably have been essential.
Responsibility for construction lay with the Organisation Todt, while the SS managed an army of 10,000 slave workers made up of Russian prisoners plus thousands of Jewish inmates brought from concentration camps such as Dachau. Working fourteen-hour shifts, seven days a week, conditions for the workers were appalling; their average life expectancy was measured in weeks. It is estimated that 30,000 people were employed in the construction of Weingut II and that between 10,000 and 20,000 perished in the process. (The involvement of slave labour in the armaments industry is discussed further in Chapter 7.) Weingut II had not been completed by the time it was occupied by American troops in April 1945.
When reviewing the effects of the CBO and the German’s dispersal programme as a whole, it is worth noting that official Allied sources estimate that 18,000 aircraft of all types were denied to the Luftwaffe in the period of intensive attacks between July 1943 and December 1944, of which 78 per cent, or 14,000, would have been fighters. Ironically, however, German aircraft production actually increased dramatically after the CBO had commenced. For example, figures for fighter aircraft production show a total of just over 2,700 in 1940, but an almost tenfold increase to approximately 25,000 in 1944, and even 5,700 for the first few months of 1945 alone. Of course there are no figures for jet aircraft production prior to 1944, but in total by the end of hostilities almost 1,300 Messerschmitt Me 262s had been produced, 364 Me 163Bs and around 116 Heinkel He 162s. The Arado Ar 234 is classified as a bomber, and of these 214 were built. This gives an estimated total figure for German jet or rocket-powered aircraft of around 2,100. And that was despite the problems of maintaining production through the bomber offensive and the disruption and disadvantages of the dispersal programme. The potential for further increases was summed up by Fedden:
The German jet engines, Junkers and BMW, were primarily designed for very large production. From an examination of their designs as well as the tooling equipment and factory layout, it appears quite possible that their estimated production of about 100,000 jet engines a year by the middle of 1946 would have been realised if they had been allowed to continue.
Hidden in the woods beside the Autobahn, this abandoned Me 262 has been stripped of its Jumo 004 engines. (NARA)
Seen from the purely engineering point of view the German aeronautical designers had produced a dazzling array of advanced and exotic flying machines in the most difficult of conditions. Fedden again:
The Mission did feel that the German aircraft industry was in the midst of some extremely interesting new developments, and that, had they been able to proceed with their new prototypes undisturbed, they would have had, within a short time, a family of very high performance interceptor fighters, as well as a family of very high speed bombers in series production.
Primarily it was through the wrecking of Germany’s manufacturing base and transportation infrastructure that the Allies ensured this didn’t happen. The official view is that the Combined Bomber Offensive had probably shortened the war by ‘some months’. It doesn’t sound that much perhaps, but as Fedden concluded: ‘The members of the Mission have come back thankful that the war ended when it did.’