Table 2.1: Statistic on German Air Activity against Britain, August 1940–June 1941
Date Major attacks Störangriffe Mines laid
Aug 1940 4 1,062 328
Sept 1940 24 (22 London) 420 669
Oct 1940 27 (all London) 21 562
Nov 1940 21 840 1,215
Dec 1940 18 369 557
Jan 1941 15 103 144
Feb 1941 6 151 376
Mar 1941 19 234 410
Apr 1941 21 412 433
May 1941 10 440 363
June 1941 6 221 647
Total 171 5,173 5,704
Source: Calculated from BA-MA, RL2. IV/33, ‘Angriffe auf England: Material-sammlung 1940–41’, monthly reports reports from Luftflotten 2, 3, 5.
The naval High Command placed great hopes on the plan to destroy at least 750,000 tonnes of shipping a month on the calculation that sinking 40 per cent of Britain’s 22 million shipping tonnage over a year would force Britain out of the war.112 The air force High Command, however, preferred to run the bombing as a unitary campaign and in the end devoted only limited resources to the naval element of the trade war. In March 1941 Göring succeeded, in the face of naval hostility, in uniting control over aircraft operating over sea under an air force commander, the Fliegerführer Atlantik, based at the French Atlantic port of Lorient. The number of serviceable aircraft available totalled only 58, including 6 of the Focke-Wulf FW200 ‘Condor’, whose initial successes were now compromised by improved British interception.113 Between July and December 1940, aircraft sank 50 merchant ships with a gross tonnage of 149,414 tonnes. Over the following six months a further 68 ships were sunk, totalling 195,894 tonnes, an average over the year of just 28,775 tonnes per month, a mere 4 per cent of what was required.114 The sea-mining campaign was similarly affected by the shortage of aircraft. In October 1940 a specialized unit, IX Fliegerkorps, was set up for mining operations, but it consisted of only 88 aircraft to cover all the waters around the British Isles. Moreover, out of the 11,167 mines dropped from the air between April 1940 and April 1941, more than one-third, 3,984, were dropped on land targets.115 Sinkings were sparse, but German airmen claimed for themselves an unverifiably large tonnage sunk by their mines throughout the campaign from 1940 to 1943, even though many of them had been laid by naval vessels and submarines.
The German Air Force saw blockade as a strategy best carried out by destroying port facilities and existing stocks rather than ships at sea, and focused its efforts on urban targets. The blockade priorities are evident from the pattern of the major (and many minor) attacks carried out during the course of the ten-month campaign. Between August 1940 and June 1941 there were 171 major raids, of which 141 were directed at ports (including London). Major port attacks at night absorbed 2,667 tonnes (86 per cent) of incendiary bombs out of a total of 3,116, and 24,535 tonnes (85 per cent) of high explosive out of a total of 28,736.116 Although some of the tonnage directed at Manchester and London was destined for non-port targets, the priority was for docks, warehouses, silos, oil storage and shipping. The economic war was seen above all as one means of closing off United States aid to Britain, which Hitler, among others, assumed to be an important source of sustenance for Britain’s war effort even before the start of Lend-Lease in March 1941.117 The flow of American goods was in reality a slender stream rather than a flood, but the German fear of American reinforcement of Britain’s war effort plays some part in explaining the willingness to continue the campaign over the difficult winter months. An assessment of the RAF made by the German Air Force operations staff in January 1941 assumed that problems caused to the supply of American aircraft and equipment must be seriously undermining British air strength and operational performance.118
For the first months of the bombing campaign the principal target was London, which was attacked for 57 nights in a row and occasionally by nuisance raids during the day. Between 7 September and 31 October, 13,685 tonnes of high explosive and Flammenbomben and 13,000 incendiary canisters were dropped on the capital.119 Unlike the early planning in the British and American bombing campaigns, the German Air Force did not draw up a list of vulnerable industrial target systems but relied more on the geographical pattern of British trade and distribution as a guide to blockade priorities, which explains the particular attention devoted to London. The one exception was the aircraft industry, and in particular the aero-engine industry, which was singled out as the priority industrial target, whose destruction would undermine RAF expansion and fighting capability. On 7 November 1940 Göring issued a new directive for the bombing campaign which left London as the principal target, but instructed the air fleets to undertake operations against the industrial region in the Midlands and Merseyside to destroy the British aircraft industry. The directive specified operations against Coventry (‘Moonlight Sonata’), Birmingham (‘Umbrella’, after Chamberlain) and Wolverhampton (‘All One Price’, a confusion for the popular Woolworths stores).120 Raids were carried out on the night of 14–15 November against Coventry and for three nights from 19–20 November against Birmingham. The raid against Wolverhampton was not attempted. For the Coventry raid 503 tonnes of bombs were dropped, including 139 1,000-kg mines, the heaviest available, and 881 canisters of incendiary bombs. The aiming point was a cluster of 30 aero-engine and component factories, including the Daimler and Alvis works. The German post-raid assessment was made difficult by the presence of cloud and smoke, but at least 12 works were identified as severely damaged and a further 8 were presumed to have suffered the same level of destruction. The close proximity of workers’ housing to the 30 aiming points resulted, according to the German raid report, in ‘considerable destruction to the residential areas’, but this was not the principal object of the attack. The raids against Birmingham totalled 762 tonnes of bombs, including 166 of the 1,000-kg and 1,563 incendiary canisters. Here again post-raid images showed that fire had destroyed much of the residential centre, and the few visible industrial targets, particularly the Rover Motor Works, were also seen to have sustained heavy damage. German estimates suggested that 60 per cent of Birmingham’s armaments production had been hit in the raids. The overall assessment of the damage sustained in the attack on Midlands industry painted an optimistic image of German successes: ‘The most important foundation of the British aircraft industry is for the present to be regarded as severely shaken.’121
The raids undertaken in November represented an escalation of the air war against inland targets. The destruction of residential districts produced high levels of civilian casualties as it had already done in London. Between September and November 1940, 18,261 people were killed in German raids.122 German estimates of damage to London reported the aerial evidence that around 50 per cent of the residential area immediately north of the docks (described in the report with the English word ‘slums’) had been rendered uninhabitable. British morale was described as ‘seriously damaged’ now that bombing was no longer confined to strictly military targets.123 Although housing as such was not a specific target and terror-bombing not its particular purpose, the tactical changes initiated in bombing attack – the use of heavy high-explosive bombs, the dropping of mines on land targets, the increased proportion of incendiaries to around half the bombload, regular nuisance raids to maximize the air-raid alarm times and provoke anxiety and fatigue – all contributed to raising the threshold of civilian disruption and casualty. But the chief reason was the declining accuracy of the bomber force under difficult night-time conditions, often in poor weather. The British Meteorological Office produced a report on aimed bombing which showed that on average there were favourable bombing conditions over Britain for only one-quarter of the year; from 20,000 feet there was reasonable visibility for only one-fifth of the year.124
The German Air Force leadership had a persistently exaggerated view of just how accurate their bombing could be under such circumstances. Maps issued to bomber crew had very precise target zones marked in a series of cross-hatched blue rectangles or r
homboids; the precise targets (a gasometer, a power station) were indicated by a small solid circle, while open red circles indicated the presence of decoy sites.125 They were expected to find these targets and not to waste their bombs. Instruction to crews in January 1941 identified inaccuracy as the principal problem confronting the force: ‘too many bombs have fallen on open ground far away from the target area ordered’.126 The RAF calculated that only between 10 per cent and 30 per cent of aircraft actually found their target (though on a fine moonlit night an estimated 47 per cent found Coventry).127 For this there were many explanations. Crews arriving at the bomber bases in the winter of 1940–41 were less experienced than many of the crews lost in combat or accident. At the training schools bomber crew were taught to fly using electronic aids to within one degree of accuracy, but by September the British understood the German beam system, which had never worked perfectly, and were beginning a programme of countermeasures to jam the signals and confuse the pilots.128 Although this did not usually prevent German bombers from finding a target city, it was sometimes the wrong one. A raid on the Rolls-Royce works in Derby in May 1941 ended up bombing the nearby city of Nottingham.129
The ability of British scientific intelligence, then its infancy, to grasp the nature of the beam system and to effect countermeasures was entirely predictable. The RAF had itself been using the German blind-landing Lorenz system since the 1930s and was familiar with its basic principles. Prisoner interrogations in the spring of 1940 alerted the British to the existence of blind-bombing technology. In June, Churchill’s scientific adviser, Frederick Lindemann, was convinced of the threat posed by the beams by a young Oxford scientist, R. V. Jones, who had been recruited by the Air Ministry as a scientific intelligence expert. Churchill himself insisted on action. An RAF unit, No. 80 Wing, was set up to research countermeasures and on 21 June 1940 the beam frequencies were finally detected. Under the codename ‘Headache’ a high-level research programme began to identify the source of the beams and to find ways of interfering with the signals. Transmitters were set up in southern and central England which could spoil the quality of the German Knickebein radio pulses, though they could not eliminate them altogether. Known as ‘aspirins’ (to cure the headache), there were 15 in place by October, 58 by summer 1941, 68 by the end of the year.130 Additional jamming stations were used for the X- and Y-Gerät, which by spring 1941 proved capable of completely misleading the pathfinder forces. By May only one-quarter of German aircraft were getting the bomb-drop signal.131
Once it became evident that the beams could be distorted or interrupted, crews were advised to avoid complete reliance on the Knickebein system and to resort to using visible markers, including woods, railways, water landmarks (estuaries, rivers, coastline), but not roads, because the roadmaps were known to be out of date.132 They were encouraged to imitate the British practice of Koppelnavigation, coupling electronic and visual methods to find the route and the target. All units were asked to choose the most experienced crews for each operation as ‘illuminators’ (Beleuchter) to guide less experienced crews, and to help them avoid British decoy fires which by the end of 1940 stretched across the English countryside.133 Over the following months reliance on electronic navigation and the pathfinders of Kampfgruppe 100 declined and crews had to resort to careful plotting and observation. This was a difficult task, as RAF crews were finding over Germany, and it made the German bomber force as a whole a much blunter instrument than it had been at the start of the campaign. At night, aircraft could achieve a relatively high concentration of bombs on a target area, but not on a precise target. German airmen shot down over Britain and held at the Trent Park interrogation centre in north London were overheard by hidden microphones to admit that the beams were no longer trusted.134 They complained among themselves that bombing accuracy was a difficult thing to achieve, demanding high levels of competence. The tension between expectation and reality is well illustrated by the following recorded exchange between a German Air Force major and a lieutenant:
M: [Knickebein] is accurate enough for night work, so that I can simply drop the bombs at that moment.
L: But if you drop the bombs at that moment, then if you are at a height of 6,000 metres the bomb will drop 1½ km farther in front, won’t it? It doesn’t drop vertically.
M: It doesn’t make any difference with such targets.
L: Well then, it can’t be so accurate.
M: No, good heavens, as I have just said, it is so difficult even to get to the point of intersection …
L: Yes, but why don’t your bombs fall accurately?
M: … you are just told to take the centre of the town and you must each find your own targets.135
German fliers knew that the levels of accuracy demanded were beyond them and that increasingly they hit the area in the target cities where the fires could be seen. It was even possible with a moment’s inattention to miss a target as large as London. ‘Göring should be told that we can’t hit the target,’ complained a German captain in another eavesdropping. ‘We must tell him all we have to put up with here …’136
This was one among many problems faced by the German bombing campaign, though few of them were dictated by the enemy, whose capacity to inflict serious damage on enemy aircraft at night remained minimal for most of the period of German attack. The bomber crews sustained high losses from accidents caused by the difficulty of long night-time flights and poor weather conditions, which could alter suddenly in the course of an operation. The number of serviceable bombers stood at almost 1,000 at the start of August, but by the end of November was down to 706. That month Kesselring himself witnessed a crash between two Ju88s, one of them a new plane, and berated his crews for ‘carelessness’. Figures for the period of poor weather from January to March 1941 show that out of 216 bombers lost and 190 damaged, 282 were as a result of flying accident.137 The often poor state of airfields in France and the Low Countries, in some cases lacking solid concrete runways, made landing and take-off especially risky. Over the winter months the German aircraft industry went through a period of crisis, making it harder to replace lost or damaged aircraft or to maintain the supply of filled bombs and mines. The planned output of bombers during the whole period of the campaign was little higher than in 1939, an average of 240 a month. Actual output was even lower, reaching a figure of only 130 bombers in January.138 The older He111 and Do17 bombers were being phased out, but a new generation of higher-performance aircraft were still in the development stage, facing accumulating technical difficulties, particularly the ill-fated Messerschmitt Me210, which was finally cancelled in April 1942. Plans for a ‘Bomber B’, a faster high-altitude bomber more suited to a strategic role, were still on the drawing board in 1940. Bombs were also a problem. In March 1941 the Air Ministry technical office warned the air force staff that there was not enough explosive to fill all the required bombs and mines, and empty bomb cases were piling up in warehouses. It was recommended filling fewer mines, which took a much larger explosive charge, in order to free explosive for regular bombs.139
The many pressures on German crews from the high accident rate, the stringent demands for accurate bombing, the injunction not to waste bombs, flying night after night in deteriorating meteorological conditions against a wide variety of scattered targets for a strategy whose end point was not entirely evident, all produced its own combat strain among the crews. Instructions to the bomber groups pointed out the necessity of giving flyers two days of proper rest after three days of combat. A long report on the medical condition of flying crews in late November 1940 noted increased signs of severe psychological and physical reaction to the pressure of constant combat and warned that the longer the campaign went on, the more likely it was that effective pilots would break down. The doctors recommended periods of leave in Paris or Brussels as a diversion, at least two weeks home leave every six months, and for all flying personnel, three weeks at a winter sports spa with plenty of good food and the best possible accommodat
ion.140 A rest home for psychiatric casualties was set up at the Hotel Boris in the Breton seaside town of Port Navalo. To give crews some sense of purpose, reports were prepared for distribution to every squadron on the estimated effects of their operations. An American report on impressions of London was circulated in early November: ‘London is still working, but on a much reduced scale … the apparatus that keeps London going is under strong pressure … The damage sustained in the past six weeks can hardly be made good in two years.’141 After the raids on Coventry and Birmingham, news was distributed about the crisis of the British steel and engineering industries, the collapsing morale of the British workforce and a widespread health crisis provoked, it was claimed, not altogether implausibly, by a combination of glassless windows and damp weather. On 23 November Göring sent out a communiqué to all the front-line squadrons assuring them that despite the difficult and tiring work in the face of enemy defences and the atrocious weather, and above all how seldom the success of operations could effectively be measured, the raid on Coventry showed that they were working for a historic victory.142 He then took a period of leave himself until the middle of January.
The Bombing War: Europe 1939–1945 Page 14